Rework refresh API and factor common display stuff out

NOT TESTED! Just compiles

Fixes #1691

8 files changed, 628 insertions, 669 deletions

diff --git a/shared-module/_stage/__init__.c b/shared-module/_stage/__init__.c
index ca71b758e..bfef165e7 100644
--- a/shared-module/_stage/__init__.c
+++ b/shared-module/_stage/__init__.c
@@ -57,7 +57,7 @@ void render_stage(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1,
                     index += 1;
                     // The buffer is full, send it.
                     if (index >= buffer_size) {
-                        display->send(display->bus, false, ((uint8_t*)buffer),
+                        display->core.send(display->core.bus, false, false, ((uint8_t*)buffer),
                                       buffer_size * 2);
                         index = 0;
                     }
@@ -67,6 +67,6 @@ void render_stage(uint16_t x0, uint16_t y0, uint16_t x1, uint16_t y1,
     }
     // Send the remaining data.
     if (index) {
-        display->send(display->bus, false, ((uint8_t*)buffer), index * 2);
+        display->core.send(display->core.bus, false, false, ((uint8_t*)buffer), index * 2);
     }
 }
diff --git a/shared-module/displayio/Display.c b/shared-module/displayio/Display.c
index fafb35f43..86800328f 100644
--- a/shared-module/displayio/Display.c
+++ b/shared-module/displayio/Display.c
@@ -33,7 +33,9 @@
 #include "shared-bindings/microcontroller/Pin.h"
 #include "shared-bindings/time/__init__.h"
 #include "shared-module/displayio/__init__.h"
+#include "shared-module/displayio/display_core.h"
 #include "supervisor/shared/display.h"
+#include "supervisor/usb.h"
 
 #include <stdint.h>
 #include <string.h>
@@ -41,48 +43,34 @@
 #include "tick.h"
 
 void common_hal_displayio_display_construct(displayio_display_obj_t* self,
-        mp_obj_t bus, uint16_t width, uint16_t height, int16_t colstart, int16_t rowstart, uint16_t rotation,
-        uint16_t color_depth, bool grayscale, bool pixels_in_byte_share_row, uint8_t bytes_per_cell, bool reverse_pixels_in_byte,
-        uint8_t set_column_command, uint8_t set_row_command,
-        uint8_t write_ram_command, uint8_t set_vertical_scroll, uint8_t* init_sequence, uint16_t init_sequence_len,
-        const mcu_pin_obj_t* backlight_pin, uint16_t brightness_command, mp_float_t brightness, bool auto_brightness,
-        bool single_byte_bounds, bool data_as_commands) {
-    self->colorspace.depth = color_depth;
-    self->colorspace.grayscale = grayscale;
-    self->colorspace.pixels_in_byte_share_row = pixels_in_byte_share_row;
-    self->colorspace.bytes_per_cell = bytes_per_cell;
-    self->colorspace.reverse_pixels_in_byte = reverse_pixels_in_byte;
+        mp_obj_t bus, uint16_t width, uint16_t height, int16_t colstart, int16_t rowstart,
+        uint16_t rotation, uint16_t color_depth, bool grayscale, bool pixels_in_byte_share_row,
+        uint8_t bytes_per_cell, bool reverse_pixels_in_byte, uint8_t set_column_command,
+        uint8_t set_row_command, uint8_t write_ram_command, uint8_t set_vertical_scroll,
+        uint8_t* init_sequence, uint16_t init_sequence_len, const mcu_pin_obj_t* backlight_pin,
+        uint16_t brightness_command, mp_float_t brightness, bool auto_brightness,
+        bool single_byte_bounds, bool data_as_commands, bool auto_refresh, uint16_t native_frames_per_second) {
+    uint16_t ram_width = 0x100;
+    uint16_t ram_height = 0x100;
+    if (single_byte_bounds) {
+        ram_width = 0xff;
+        ram_height = 0xff;
+    }
+    displayio_display_core_construct(&self->core, bus, width, height, ram_width, ram_height, colstart, rowstart, rotation,
+        color_depth, grayscale, pixels_in_byte_share_row, bytes_per_cell, reverse_pixels_in_byte);
+
     self->set_column_command = set_column_command;
     self->set_row_command = set_row_command;
     self->write_ram_command = write_ram_command;
-    self->refresh = false;
-    self->current_group = NULL;
-    self->colstart = colstart;
-    self->rowstart = rowstart;
     self->brightness_command = brightness_command;
     self->auto_brightness = auto_brightness;
     self->data_as_commands = data_as_commands;
-    self->single_byte_bounds = single_byte_bounds;
-
-    if (MP_OBJ_IS_TYPE(bus, &displayio_parallelbus_type)) {
-        self->begin_transaction = common_hal_displayio_parallelbus_begin_transaction;
-        self->send = common_hal_displayio_parallelbus_send;
-        self->end_transaction = common_hal_displayio_parallelbus_end_transaction;
-    } else if (MP_OBJ_IS_TYPE(bus, &displayio_fourwire_type)) {
-        self->begin_transaction = common_hal_displayio_fourwire_begin_transaction;
-        self->send = common_hal_displayio_fourwire_send;
-        self->end_transaction = common_hal_displayio_fourwire_end_transaction;
-    } else if (MP_OBJ_IS_TYPE(bus, &displayio_i2cdisplay_type)) {
-        self->begin_transaction = common_hal_displayio_i2cdisplay_begin_transaction;
-        self->send = common_hal_displayio_i2cdisplay_send;
-        self->end_transaction = common_hal_displayio_i2cdisplay_end_transaction;
-    } else {
-        mp_raise_ValueError(translate("Unsupported display bus type"));
-    }
-    self->bus = bus;
+
+    self->native_frames_per_second = native_frames_per_second;
+    self->native_frame_time = 1000 / native_frames_per_second;
 
     uint32_t i = 0;
-    while (!self->begin_transaction(self->bus)) {
+    while (!displayio_display_core_begin_transaction(&self->core)) {
         RUN_BACKGROUND_TASKS;
     }
     while (i < init_sequence_len) {
@@ -95,10 +83,10 @@ void common_hal_displayio_display_construct(displayio_display_obj_t* self,
             uint8_t full_command[data_size + 1];
             full_command[0] = cmd[0];
             memcpy(full_command + 1, data, data_size);
-            self->send(self->bus, true, true, full_command, data_size + 1);
+            self->core.send(self->core.bus, true, true, full_command, data_size + 1);
         } else {
-            self->send(self->bus, true, true, cmd, 1);
-            self->send(self->bus, false, false, data, data_size);
+            self->core.send(self->core.bus, true, true, cmd, 1);
+            self->core.send(self->core.bus, false, false, data, data_size);
         }
         uint16_t delay_length_ms = 10;
         if (delay) {
@@ -111,33 +99,10 @@ void common_hal_displayio_display_construct(displayio_display_obj_t* self,
         common_hal_time_delay_ms(delay_length_ms);
         i += 2 + data_size;
     }
-    self->end_transaction(self->bus);
+    self->core.end_transaction(self->core.bus);
 
     supervisor_start_terminal(width, height);
 
-    self->width = width;
-    self->height = height;
-    self->rotation = rotation % 360;
-    self->transform.x = 0;
-    self->transform.y = 0;
-    self->transform.scale = 1;
-    self->transform.mirror_x = false;
-    self->transform.mirror_y = false;
-    self->transform.transpose_xy = false;
-    if (rotation == 0 || rotation == 180) {
-        if (rotation == 180) {
-            self->transform.mirror_x = true;
-            self->transform.mirror_y = true;
-        }
-    } else {
-        self->transform.transpose_xy = true;
-        if (rotation == 270) {
-            self->transform.mirror_y = true;
-        } else {
-            self->transform.mirror_x = true;
-        }
-    }
-
     // Always set the backlight type in case we're reusing memory.
     self->backlight_inout.base.type = &mp_type_NoneType;
     if (backlight_pin != NULL && common_hal_mcu_pin_is_free(backlight_pin)) {
@@ -158,101 +123,98 @@ void common_hal_displayio_display_construct(displayio_display_obj_t* self,
         self->current_brightness = -1.0;
     }
 
-    self->area.x1 = 0;
-    self->area.y1 = 0;
-    self->area.next = NULL;
-
-    self->transform.dx = 1;
-    self->transform.dy = 1;
-    if (self->transform.transpose_xy) {
-        self->area.x2 = height;
-        self->area.y2 = width;
-        if (self->transform.mirror_x) {
-            self->transform.x = height;
-            self->transform.dx = -1;
-        }
-        if (self->transform.mirror_y) {
-            self->transform.y = width;
-            self->transform.dy = -1;
-        }
-    } else {
-        self->area.x2 = width;
-        self->area.y2 = height;
-        if (self->transform.mirror_x) {
-            self->transform.x = width;
-            self->transform.dx = -1;
-        }
-        if (self->transform.mirror_y) {
-            self->transform.y = height;
-            self->transform.dy = -1;
-        }
-    }
-
     // Set the group after initialization otherwise we may send pixels while we delay in
     // initialization.
     common_hal_displayio_display_show(self, &circuitpython_splash);
 }
 
 bool common_hal_displayio_display_show(displayio_display_obj_t* self, displayio_group_t* root_group) {
-    if (root_group == NULL) {
-        if (!circuitpython_splash.in_group) {
-            root_group = &circuitpython_splash;
-        } else if (self->current_group == &circuitpython_splash) {
-            return false;
+    return displayio_display_core_show(&self->core, root_group);
+}
+
+uint16_t common_hal_displayio_display_get_width(displayio_display_obj_t* self){
+    return displayio_display_core_get_width(&self->core);
+}
+
+uint16_t common_hal_displayio_display_get_height(displayio_display_obj_t* self){
+    return displayio_display_core_get_height(&self->core);
+}
+
+bool common_hal_displayio_display_get_auto_brightness(displayio_display_obj_t* self) {
+    return self->auto_brightness;
+}
+
+void common_hal_displayio_display_set_auto_brightness(displayio_display_obj_t* self, bool auto_brightness) {
+    self->auto_brightness = auto_brightness;
+}
+
+mp_float_t common_hal_displayio_display_get_brightness(displayio_display_obj_t* self) {
+    return self->current_brightness;
+}
+
+bool common_hal_displayio_display_set_brightness(displayio_display_obj_t* self, mp_float_t brightness) {
+    self->updating_backlight = true;
+    bool ok = false;
+    if (self->backlight_pwm.base.type == &pulseio_pwmout_type) {
+        common_hal_pulseio_pwmout_set_duty_cycle(&self->backlight_pwm, (uint16_t) (0xffff * brightness));
+        ok = true;
+    } else if (self->backlight_inout.base.type == &digitalio_digitalinout_type) {
+        common_hal_digitalio_digitalinout_set_value(&self->backlight_inout, brightness > 0.99);
+        ok = true;
+    } else if (self->brightness_command != NO_BRIGHTNESS_COMMAND) {
+        ok = displayio_display_core_begin_transaction(&self->core);
+        if (ok) {
+            if (self->data_as_commands) {
+                uint8_t set_brightness[2] = {self->brightness_command, (uint8_t) (0xff * brightness)};
+                self->core.send(self->core.bus, true, true, set_brightness, 2);
+            } else {
+                uint8_t command = self->brightness_command;
+                uint8_t hex_brightness = 0xff * brightness;
+                self->core.send(self->core.bus, true, true, &command, 1);
+                self->core.send(self->core.bus, false, false, &hex_brightness, 1);
+            }
+            displayio_display_core_end_transaction(&self->core);
         }
+
     }
-    if (root_group == self->current_group) {
-        return true;
-    }
-    if (root_group != NULL && root_group->in_group) {
-        return false;
-    }
-    if (self->current_group != NULL) {
-        self->current_group->in_group = false;
+    self->updating_backlight = false;
+    if (ok) {
+        self->current_brightness = brightness;
     }
+    return ok;
+}
 
-    if (root_group != NULL) {
-        displayio_group_update_transform(root_group, &self->transform);
-        root_group->in_group = true;
-    }
-    self->current_group = root_group;
-    self->full_refresh = true;
-    common_hal_displayio_display_refresh_soon(self);
-    return true;
+mp_obj_t common_hal_displayio_display_get_bus(displayio_display_obj_t* self) {
+    return self->core.bus;
 }
 
-const displayio_area_t* displayio_display_get_refresh_areas(displayio_display_obj_t *self) {
-    if (self->full_refresh) {
-        self->area.next = NULL;
-        return &self->area;
+STATIC const displayio_area_t* _get_refresh_areas(displayio_display_obj_t *self) {
+    if (self->core.full_refresh) {
+        self->core.area.next = NULL;
+        return &self->core.area;
     } else {
-        if (self->current_group == NULL || self->current_group->base.type != &displayio_group_type) {
-            asm("bkpt");
-        }
-        return displayio_group_get_refresh_areas(self->current_group, NULL);
+        return displayio_group_get_refresh_areas(self->core.current_group, NULL);
     }
 }
 
-int32_t common_hal_displayio_display_wait_for_frame(displayio_display_obj_t* self) {
-    uint64_t last_refresh = self->last_refresh;
-    // Don't try to refresh if we got an exception.
-    while (last_refresh == self->last_refresh && MP_STATE_VM(mp_pending_exception) == NULL) {
-        RUN_BACKGROUND_TASKS;
+STATIC void _send_pixels(displayio_display_obj_t* self, uint8_t* pixels, uint32_t length) {
+    if (!self->data_as_commands) {
+        self->core.send(self->core.bus, true, true, &self->write_ram_command, 1);
     }
-    return 0;
+    self->core.send(self->core.bus, false, false, pixels, length);
 }
 
-STATIC bool refresh_area(displayio_display_obj_t* display, const displayio_area_t* area) {
+STATIC bool _refresh_area(displayio_display_obj_t* self, const displayio_area_t* area) {
     uint16_t buffer_size = 128; // In uint32_ts
 
     displayio_area_t clipped;
     // Clip the area to the display by overlapping the areas. If there is no overlap then we're done.
-    if (!displayio_display_clip_area(display, area, &clipped)) {
+    if (!displayio_display_core_clip_area(&self->core, area, &clipped)) {
         return true;
     }
     uint16_t subrectangles = 1;
     uint16_t rows_per_buffer = displayio_area_height(&clipped);
-    uint8_t pixels_per_word = (sizeof(uint32_t) * 8) / display->colorspace.depth;
+    uint8_t pixels_per_word = (sizeof(uint32_t) * 8) / self->core.colorspace.depth;
     uint16_t pixels_per_buffer = displayio_area_size(&clipped);
     if (displayio_area_size(&clipped) > buffer_size * pixels_per_word) {
         rows_per_buffer = buffer_size * pixels_per_word / displayio_area_width(&clipped);
@@ -260,8 +222,8 @@ STATIC bool refresh_area(displayio_display_obj_t* display, const displayio_area_
             rows_per_buffer = 1;
         }
         // If pixels are packed by column then ensure rows_per_buffer is on a byte boundary.
-        if (display->colorspace.depth < 8 && !display->colorspace.pixels_in_byte_share_row) {
-            uint8_t pixels_per_byte = 8 / display->colorspace.depth;
+        if (self->core.colorspace.depth < 8 && !self->core.colorspace.pixels_in_byte_share_row) {
+            uint8_t pixels_per_byte = 8 / self->core.colorspace.depth;
             if (rows_per_buffer % pixels_per_byte != 0) {
                 rows_per_buffer -= rows_per_buffer % pixels_per_byte;
             }
@@ -296,15 +258,13 @@ STATIC bool refresh_area(displayio_display_obj_t* display, const displayio_area_
         }
         remaining_rows -= rows_per_buffer;
 
-        displayio_display_begin_transaction(display);
-        displayio_display_set_region_to_update(display, &subrectangle);
-        displayio_display_end_transaction(display);
+        displayio_display_core_set_region_to_update(&self->core, self->set_column_command, self->set_row_command, NO_COMMAND, NO_COMMAND, self->data_as_commands, false, &subrectangle);
 
         uint16_t subrectangle_size_bytes;
-        if (display->colorspace.depth >= 8) {
-            subrectangle_size_bytes = displayio_area_size(&subrectangle) * (display->colorspace.depth / 8);
+        if (self->core.colorspace.depth >= 8) {
+            subrectangle_size_bytes = displayio_area_size(&subrectangle) * (self->core.colorspace.depth / 8);
         } else {
-            subrectangle_size_bytes = displayio_area_size(&subrectangle) / (8 / display->colorspace.depth);
+            subrectangle_size_bytes = displayio_area_size(&subrectangle) / (8 / self->core.colorspace.depth);
         }
 
         for (uint16_t k = 0; k < mask_length; k++) {
@@ -314,14 +274,16 @@ STATIC bool refresh_area(displayio_display_obj_t* display, const displayio_area_
             buffer[k] = 0x00000000;
         }
 
-        displayio_display_fill_area(display, &subrectangle, mask, buffer);
+        displayio_display_core_fill_area(&self->core, &subrectangle, mask, buffer);
 
-        if (!displayio_display_begin_transaction(display)) {
-            // Can't acquire display bus; skip the rest of the data. Try next display.
+        // Can't acquire display bus; skip the rest of the data.
+        if (!displayio_display_core_bus_free(&self->core)) {
             return false;
         }
-        displayio_display_send_pixels(display, (uint8_t*) buffer, subrectangle_size_bytes);
-        displayio_display_end_transaction(display);
+
+        displayio_display_core_begin_transaction(&self->core);
+        _send_pixels(self, (uint8_t*) buffer, subrectangle_size_bytes);
+        displayio_display_core_end_transaction(&self->core);
 
         // TODO(tannewt): Make refresh displays faster so we don't starve other
         // background tasks.
@@ -330,182 +292,59 @@ STATIC bool refresh_area(displayio_display_obj_t* display, const displayio_area_
     return true;
 }
 
-STATIC void refresh_display(displayio_display_obj_t* self) {
-    if (!displayio_display_begin_transaction(self)) {
+STATIC void _refresh_display(displayio_display_obj_t* self) {
+    if (!displayio_display_core_bus_free(&self->core)) {
         // Can't acquire display bus; skip updating this display. Try next display.
-        continue;
+        return;
     }
-    displayio_display_end_transaction(self);
-    displayio_display_start_refresh(self);
-    const displayio_area_t* current_area = displayio_display_get_refresh_areas(self);
+    displayio_display_core_start_refresh(&self->core);
+    const displayio_area_t* current_area = _get_refresh_areas(self);
     while (current_area != NULL) {
-        refresh_area(self, current_area);
+        _refresh_area(self, current_area);
         current_area = current_area->next;
     }
-    displayio_display_finish_refresh(self);
-}
-
-void common_hal_displayio_display_refresh(displayio_display_obj_t* self) {
-    // Time to refresh at specified frame rate?
-    while (!displayio_display_frame_queued(self)) {
-        // Too soon. Try next display.
-        continue;
-    }
-    refresh_display(self);
-}
-
-bool common_hal_displayio_display_get_auto_brightness(displayio_display_obj_t* self) {
-    return self->auto_brightness;
-}
-
-uint16_t common_hal_displayio_display_get_width(displayio_display_obj_t* self){
-    return self->width;
-}
-
-uint16_t common_hal_displayio_display_get_height(displayio_display_obj_t* self){
-    return self->height;
+    displayio_display_core_finish_refresh(&self->core);
 }
 
 uint16_t common_hal_displayio_display_get_rotation(displayio_display_obj_t* self){
-    return self->rotation;
-}
-
-void common_hal_displayio_display_set_auto_brightness(displayio_display_obj_t* self, bool auto_brightness) {
-    self->auto_brightness = auto_brightness;
-}
-
-mp_float_t common_hal_displayio_display_get_brightness(displayio_display_obj_t* self) {
-    return self->current_brightness;
+    return self->core.rotation;
 }
 
-bool common_hal_displayio_display_set_brightness(displayio_display_obj_t* self, mp_float_t brightness) {
-    self->updating_backlight = true;
-    bool ok = false;
-    if (self->backlight_pwm.base.type == &pulseio_pwmout_type) {
-        common_hal_pulseio_pwmout_set_duty_cycle(&self->backlight_pwm, (uint16_t) (0xffff * brightness));
-        ok = true;
-    } else if (self->backlight_inout.base.type == &digitalio_digitalinout_type) {
-        common_hal_digitalio_digitalinout_set_value(&self->backlight_inout, brightness > 0.99);
-        ok = true;
-    } else if (self->brightness_command != NO_BRIGHTNESS_COMMAND) {
-        ok = self->begin_transaction(self->bus);
-        if (ok) {
-            if (self->data_as_commands) {
-                uint8_t set_brightness[2] = {self->brightness_command, (uint8_t) (0xff * brightness)};
-                self->send(self->bus, true, true, set_brightness, 2);
-            } else {
-                uint8_t command = self->brightness_command;
-                uint8_t hex_brightness = 0xff * brightness;
-                self->send(self->bus, true, true, &command, 1);
-                self->send(self->bus, false, false, &hex_brightness, 1);
-            }
-            self->end_transaction(self->bus);
+void common_hal_displayio_display_refresh(displayio_display_obj_t* self, uint32_t target_frame_time, uint32_t maximum_frame_time) {
+    if (!self->auto_refresh) {
+        uint64_t current_time = ticks_ms;
+        uint32_t current_frame_time = current_time - self->core.last_refresh;
+        // Test to see if the real frame time is below our minimum.
+        if (current_frame_time > maximum_frame_time) {
+            mp_raise_RuntimeError(translate("Below minimum frame rate"));
         }
-
-    }
-    self->updating_backlight = false;
-    if (ok) {
-        self->current_brightness = brightness;
-    }
-    return ok;
-}
-
-bool displayio_display_begin_transaction(displayio_display_obj_t* self) {
-    return self->begin_transaction(self->bus);
-}
-
-void displayio_display_end_transaction(displayio_display_obj_t* self) {
-    self->end_transaction(self->bus);
-}
-
-void displayio_display_set_region_to_update(displayio_display_obj_t* self, displayio_area_t* area) {
-    uint16_t x1 = area->x1;
-    uint16_t x2 = area->x2;
-    uint16_t y1 = area->y1;
-    uint16_t y2 = area->y2;
-    // Collapse down the dimension where multiple pixels are in a byte.
-    if (self->colorspace.depth < 8) {
-        uint8_t pixels_per_byte = 8 / self->colorspace.depth;
-        if (self->colorspace.pixels_in_byte_share_row) {
-            x1 /= pixels_per_byte * self->colorspace.bytes_per_cell;
-            x2 /= pixels_per_byte * self->colorspace.bytes_per_cell;
-        } else {
-            y1 /= pixels_per_byte * self->colorspace.bytes_per_cell;
-            y2 /= pixels_per_byte * self->colorspace.bytes_per_cell;
+        uint32_t current_call_time = current_time - self->last_refresh_call;
+        self->last_refresh_call = current_time;
+        // Skip the actual refresh to help catch up.
+        if (current_call_time > target_frame_time) {
+            return;
+        }
+        uint32_t remaining_time = target_frame_time - (current_frame_time % target_frame_time);
+        // We're ahead of the game so wait until we align with the frame rate.
+        while (ticks_ms - self->last_refresh_call < remaining_time) {
+            #ifdef MICROPY_VM_HOOK_LOOP
+            MICROPY_VM_HOOK_LOOP ;
+            #endif
         }
     }
-
-    // Set column.
-    uint8_t data[5];
-    data[0] = self->set_column_command;
-    uint8_t data_length = 1;
-    if (!self->data_as_commands) {
-        self->send(self->bus, true, true, data, 1);
-        data_length = 0;
-    }
-    if (self->single_byte_bounds) {
-        data[data_length++] = x1 + self->colstart;
-        data[data_length++] = x2 - 1 + self->colstart;
-    } else {
-        x1 += self->colstart;
-        x2 += self->colstart - 1;
-        data[data_length++] = x1 >> 8;
-        data[data_length++] = x1 & 0xff;
-        data[data_length++] = x2 >> 8;
-        data[data_length++] = x2 & 0xff;
-    }
-    self->send(self->bus, self->data_as_commands, self->data_as_commands, data, data_length);
-
-    // Set row.
-    data[0] = self->set_row_command;
-    data_length = 1;
-    if (!self->data_as_commands) {
-        self->send(self->bus, true, true, data, 1);
-        data_length = 0;
-    }
-    if (self->single_byte_bounds) {
-        data[data_length++] = y1 + self->rowstart;
-        data[data_length++] = y2 - 1 + self->rowstart;
-    } else {
-        y1 += self->rowstart;
-        y2 += self->rowstart - 1;
-        data[data_length++] = y1 >> 8;
-        data[data_length++] = y1 & 0xff;
-        data[data_length++] = y2 >> 8;
-        data[data_length++] = y2 & 0xff;
-    }
-    self->send(self->bus, self->data_as_commands, self->data_as_commands, data, data_length);
-}
-
-void displayio_display_start_refresh(displayio_display_obj_t* self) {
-    self->last_refresh = ticks_ms;
-}
-
-bool displayio_display_frame_queued(displayio_display_obj_t* self) {
-    if (self->current_group == NULL) {
-        return false;
-    }
-    // Refresh at ~60 fps.
-    return (ticks_ms - self->last_refresh) > 16;
+    _refresh_display(self);
 }
 
-void displayio_display_finish_refresh(displayio_display_obj_t* self) {
-    if (self->current_group != NULL) {
-        displayio_group_finish_refresh(self->current_group);
-    }
-    self->refresh = false;
-    self->full_refresh = false;
-    self->last_refresh = ticks_ms;
+bool common_hal_displayio_display_get_auto_refresh(displayio_display_obj_t* self) {
+    return self->auto_refresh;
 }
 
-void displayio_display_send_pixels(displayio_display_obj_t* self, uint8_t* pixels, uint32_t length) {
-    if (!self->data_as_commands) {
-        self->send(self->bus, true, true, &self->write_ram_command, 1);
-    }
-    self->send(self->bus, false, false, pixels, length);
+void common_hal_displayio_display_set_auto_refresh(displayio_display_obj_t* self,
+                                                   bool auto_refresh) {
+    self->auto_refresh = auto_refresh;
 }
 
-void displayio_display_update_backlight(displayio_display_obj_t* self) {
+STATIC void _update_backlight(displayio_display_obj_t* self) {
     if (!self->auto_brightness || self->updating_backlight) {
         return;
     }
@@ -520,17 +359,15 @@ void displayio_display_update_backlight(displayio_display_obj_t* self) {
 }
 
 void displayio_display_background(displayio_display_obj_t* self) {
-    displayio_display_update_backlight(self);
+    _update_backlight(self);
 
-    if (self->auto_refresh && (ticks_ms - self->last_refresh) > 16) {
-        display_refresh(self);
+    if (self->auto_refresh && (ticks_ms - self->core.last_refresh) > self->native_frame_time) {
+        _refresh_display(self);
     }
 }
 
 void release_display(displayio_display_obj_t* self) {
-    if (self->current_group != NULL) {
-        self->current_group->in_group = false;
-    }
+    release_display_core(&self->core);
     if (self->backlight_pwm.base.type == &pulseio_pwmout_type) {
         common_hal_pulseio_pwmout_reset_ok(&self->backlight_pwm);
         common_hal_pulseio_pwmout_deinit(&self->backlight_pwm);
@@ -539,34 +376,6 @@ void release_display(displayio_display_obj_t* self) {
     }
 }
 
-bool displayio_display_fill_area(displayio_display_obj_t *self, displayio_area_t* area, uint32_t* mask, uint32_t *buffer) {
-    return displayio_group_fill_area(self->current_group, &self->colorspace, area, mask, buffer);
-}
-
-bool displayio_display_clip_area(displayio_display_obj_t *self, const displayio_area_t* area, displayio_area_t* clipped) {
-    bool overlaps = displayio_area_compute_overlap(&self->area, area, clipped);
-    if (!overlaps) {
-        return false;
-    }
-    // Expand the area if we have multiple pixels per byte and we need to byte
-    // align the bounds.
-    if (self->colorspace.depth < 8) {
-        uint8_t pixels_per_byte = 8 / self->colorspace.depth * self->colorspace.bytes_per_cell;
-        if (self->colorspace.pixels_in_byte_share_row) {
-            if (clipped->x1 % pixels_per_byte != 0) {
-                clipped->x1 -= clipped->x1 % pixels_per_byte;
-            }
-            if (clipped->x2 % pixels_per_byte != 0) {
-                clipped->x2 += pixels_per_byte - clipped->x2 % pixels_per_byte;
-            }
-        } else {
-            if (clipped->y1 % pixels_per_byte != 0) {
-                clipped->y1 -= clipped->y1 % pixels_per_byte;
-            }
-            if (clipped->y2 % pixels_per_byte != 0) {
-                clipped->y2 += pixels_per_byte - clipped->y2 % pixels_per_byte;
-            }
-        }
-    }
-    return true;
+void displayio_display_collect_ptrs(displayio_display_obj_t* self) {
+    displayio_display_core_collect_ptrs(&self->core);
 }
diff --git a/shared-module/displayio/Display.h b/shared-module/displayio/Display.h
index db0a23012..cff566a61 100644
--- a/shared-module/displayio/Display.h
+++ b/shared-module/displayio/Display.h
@@ -32,46 +32,33 @@
 #include "shared-bindings/pulseio/PWMOut.h"
 
 #include "shared-module/displayio/area.h"
-
-typedef bool (*display_bus_begin_transaction)(mp_obj_t bus);
-typedef void (*display_bus_send)(mp_obj_t bus, bool command, bool toggle_every_byte, uint8_t *data, uint32_t data_length);
-typedef void (*display_bus_end_transaction)(mp_obj_t bus);
+#include "shared-module/displayio/display_core.h"
 
 typedef struct {
     mp_obj_base_t base;
-    mp_obj_t bus;
-    displayio_group_t *current_group;
-    uint64_t last_refresh;
-    display_bus_begin_transaction begin_transaction;
-    display_bus_send send;
-    display_bus_end_transaction end_transaction;
+    displayio_display_core_t core;
     union {
         digitalio_digitalinout_obj_t backlight_inout;
         pulseio_pwmout_obj_t backlight_pwm;
     };
     uint64_t last_backlight_refresh;
-    displayio_buffer_transform_t transform;
-    displayio_area_t area;
+    uint64_t last_refresh_call;
     mp_float_t current_brightness;
-    uint16_t width;
-    uint16_t height;
-    uint16_t rotation;
-    _displayio_colorspace_t colorspace;
-    int16_t colstart;
-    int16_t rowstart;
     uint16_t brightness_command;
+    uint16_t native_frames_per_second;
+    uint16_t native_frame_time;
     uint8_t set_column_command;
     uint8_t set_row_command;
     uint8_t write_ram_command;
     bool auto_refresh;
-    bool single_byte_bounds;
     bool data_as_commands;
     bool auto_brightness;
     bool updating_backlight;
-    bool full_refresh; // New group means we need to refresh the whole display.
 } displayio_display_obj_t;
 
 void displayio_display_background(displayio_display_obj_t* self);
 void release_display(displayio_display_obj_t* self);
 
+void displayio_display_collect_ptrs(displayio_display_obj_t* self);
+
 #endif // MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_DISPLAY_H
diff --git a/shared-module/displayio/EPaperDisplay.c b/shared-module/displayio/EPaperDisplay.c
index 434adbdf4..6ff060a6a 100644
--- a/shared-module/displayio/EPaperDisplay.c
+++ b/shared-module/displayio/EPaperDisplay.c
@@ -50,18 +50,14 @@ void common_hal_displayio_epaperdisplay_construct(displayio_epaperdisplay_obj_t*
         uint16_t set_current_column_command, uint16_t set_current_row_command,
         uint16_t write_black_ram_command, bool black_bits_inverted, uint16_t write_color_ram_command, bool color_bits_inverted, uint32_t highlight_color, uint16_t refresh_display_command,
         const mcu_pin_obj_t* busy_pin, bool busy_state, mp_float_t seconds_per_frame, bool always_toggle_chip_select) {
-    self->colorspace.depth = 1;
-    self->colorspace.grayscale = true;
-    self->colorspace.pixels_in_byte_share_row = true;
-    self->colorspace.bytes_per_cell = 1;
-    self->colorspace.reverse_pixels_in_byte = true;
-
     if (highlight_color != 0x000000) {
-        self->colorspace.tricolor = true;
-        self->colorspace.tricolor_hue = displayio_colorconverter_compute_hue(highlight_color);
-        self->colorspace.tricolor_luma = displayio_colorconverter_compute_luma(highlight_color);
+        self->core.colorspace.tricolor = true;
+        self->core.colorspace.tricolor_hue = displayio_colorconverter_compute_hue(highlight_color);
+        self->core.colorspace.tricolor_luma = displayio_colorconverter_compute_luma(highlight_color);
     }
 
+    displayio_display_core_construct(&self->core, bus, width, height, ram_width, ram_height, colstart, rowstart, rotation, 1, true, true, 1, true);
+
     self->set_column_window_command = set_column_window_command;
     self->set_row_window_command = set_row_window_command;
     self->set_current_column_command = set_current_column_command;
@@ -72,10 +68,6 @@ void common_hal_displayio_epaperdisplay_construct(displayio_epaperdisplay_obj_t*
     self->color_bits_inverted = color_bits_inverted;
     self->refresh_display_command = refresh_display_command;
     self->busy_state = busy_state;
-    self->refresh = true;
-    self->current_group = NULL;
-    self->colstart = colstart;
-    self->rowstart = rowstart;
     self->refreshing = false;
     self->milliseconds_per_frame = seconds_per_frame * 1000;
     self->always_toggle_chip_select = always_toggle_chip_select;
@@ -85,88 +77,6 @@ void common_hal_displayio_epaperdisplay_construct(displayio_epaperdisplay_obj_t*
     self->stop_sequence = stop_sequence;
     self->stop_sequence_len = stop_sequence_len;
 
-
-    if (MP_OBJ_IS_TYPE(bus, &displayio_parallelbus_type)) {
-        self->bus_reset = common_hal_displayio_parallelbus_reset;
-        self->bus_free = common_hal_displayio_parallelbus_bus_free;
-        self->begin_transaction = common_hal_displayio_parallelbus_begin_transaction;
-        self->send = common_hal_displayio_parallelbus_send;
-        self->end_transaction = common_hal_displayio_parallelbus_end_transaction;
-    } else if (MP_OBJ_IS_TYPE(bus, &displayio_fourwire_type)) {
-        self->bus_reset = common_hal_displayio_fourwire_reset;
-        self->bus_free = common_hal_displayio_fourwire_bus_free;
-        self->begin_transaction = common_hal_displayio_fourwire_begin_transaction;
-        self->send = common_hal_displayio_fourwire_send;
-        self->end_transaction = common_hal_displayio_fourwire_end_transaction;
-    } else if (MP_OBJ_IS_TYPE(bus, &displayio_i2cdisplay_type)) {
-        self->bus_reset = common_hal_displayio_i2cdisplay_reset;
-        self->bus_free = common_hal_displayio_i2cdisplay_bus_free;
-        self->begin_transaction = common_hal_displayio_i2cdisplay_begin_transaction;
-        self->send = common_hal_displayio_i2cdisplay_send;
-        self->end_transaction = common_hal_displayio_i2cdisplay_end_transaction;
-    } else {
-        mp_raise_ValueError(translate("Unsupported display bus type"));
-    }
-    self->bus = bus;
-
-    supervisor_start_terminal(width, height);
-
-    self->width = width;
-    self->height = height;
-    rotation = rotation % 360;
-    self->transform.x = 0;
-    self->transform.y = 0;
-    self->transform.scale = 1;
-    self->transform.mirror_x = false;
-    self->transform.mirror_y = false;
-    self->transform.transpose_xy = false;
-    if (rotation == 0 || rotation == 180) {
-        if (rotation == 180) {
-            self->transform.mirror_x = true;
-            self->transform.mirror_y = true;
-        }
-    } else {
-        self->transform.transpose_xy = true;
-        if (rotation == 270) {
-            self->transform.mirror_y = true;
-        } else {
-            self->transform.mirror_x = true;
-        }
-    }
-
-    self->ram_width = ram_width;
-    self->ram_height = ram_height;
-
-    self->area.x1 = 0;
-    self->area.y1 = 0;
-    self->area.next = NULL;
-
-    self->transform.dx = 1;
-    self->transform.dy = 1;
-    if (self->transform.transpose_xy) {
-        self->area.x2 = height;
-        self->area.y2 = width;
-        if (self->transform.mirror_x) {
-            self->transform.x = height;
-            self->transform.dx = -1;
-        }
-        if (self->transform.mirror_y) {
-            self->transform.y = width;
-            self->transform.dy = -1;
-        }
-    } else {
-        self->area.x2 = width;
-        self->area.y2 = height;
-        if (self->transform.mirror_x) {
-            self->transform.x = width;
-            self->transform.dx = -1;
-        }
-        if (self->transform.mirror_y) {
-            self->transform.y = height;
-            self->transform.dy = -1;
-        }
-    }
-
     self->busy.base.type = &mp_type_NoneType;
     if (busy_pin != NULL) {
         self->busy.base.type = &digitalio_digitalinout_type;
@@ -179,77 +89,37 @@ void common_hal_displayio_epaperdisplay_construct(displayio_epaperdisplay_obj_t*
         // TODO: Clear
     }
 
+    supervisor_start_terminal(width, height);
+
     // Set the group after initialization otherwise we may send pixels while we delay in
     // initialization.
     common_hal_displayio_epaperdisplay_show(self, &circuitpython_splash);
 }
 
 bool common_hal_displayio_epaperdisplay_show(displayio_epaperdisplay_obj_t* self, displayio_group_t* root_group) {
-    if (root_group == NULL && !circuitpython_splash.in_group) {
-        root_group = &circuitpython_splash;
-    }
-    if (root_group == self->current_group) {
-        return true;
-    }
-    if (root_group != NULL && root_group->in_group) {
-        return false;
-    }
-    if (self->current_group != NULL) {
-        self->current_group->in_group = false;
-    }
-    if (root_group != NULL) {
-        displayio_group_update_transform(root_group, &self->transform);
-        root_group->in_group = true;
-        self->current_group = root_group;
-    }
-    self->full_refresh = true;
-    return true;
+    return displayio_display_core_show(&self->core, root_group);
 }
 
 const displayio_area_t* displayio_epaperdisplay_get_refresh_areas(displayio_epaperdisplay_obj_t *self) {
     const displayio_area_t* first_area;
-    if (self->current_group == NULL || self->current_group->base.type != &displayio_group_type) {
-        asm("bkpt");
-    }
-    if (self->full_refresh) {
-        first_area = &self->area;
+    if (self->core.full_refresh) {
+        first_area = &self->core.area;
     } else {
-        first_area = displayio_group_get_refresh_areas(self->current_group, NULL);
+        first_area = displayio_group_get_refresh_areas(self->core.current_group, NULL);
     }
     if (first_area != NULL && self->set_row_window_command == NO_COMMAND) {
-        self->area.next = NULL;
-        return &self->area;
+        self->core.area.next = NULL;
+        return &self->core.area;
     }
     return first_area;
 }
 
-int32_t common_hal_displayio_epaperdisplay_wait_for_frame(displayio_epaperdisplay_obj_t* self) {
-    uint64_t last_refresh = self->last_refresh;
-    // Don't try to refresh if we got an exception.
-    while (last_refresh == self->last_refresh && MP_STATE_VM(mp_pending_exception) == NULL) {
-        MICROPY_VM_HOOK_LOOP
-    }
-    return 0;
-}
-
 uint16_t common_hal_displayio_epaperdisplay_get_width(displayio_epaperdisplay_obj_t* self){
-    return self->width;
+    return displayio_display_core_get_width(&self->core);
 }
 
 uint16_t common_hal_displayio_epaperdisplay_get_height(displayio_epaperdisplay_obj_t* self){
-    return self->height;
-}
-
-bool displayio_epaperdisplay_bus_free(displayio_epaperdisplay_obj_t *self) {
-    return self->bus_free(self->bus);
-}
-
-bool displayio_epaperdisplay_begin_transaction(displayio_epaperdisplay_obj_t* self) {
-    return self->begin_transaction(self->bus);
-}
-
-void displayio_epaperdisplay_end_transaction(displayio_epaperdisplay_obj_t* self) {
-    self->end_transaction(self->bus);
+    return displayio_display_core_get_height(&self->core);
 }
 
 STATIC void wait_for_busy(displayio_epaperdisplay_obj_t* self) {
@@ -271,10 +141,10 @@ STATIC void send_command_sequence(displayio_epaperdisplay_obj_t* self, bool shou
         bool delay = (data_size & DELAY) != 0;
         data_size &= ~DELAY;
         uint8_t *data = cmd + 2;
-        self->begin_transaction(self->bus);
-        self->send(self->bus, true, self->always_toggle_chip_select, cmd, 1);
-        self->send(self->bus, false, self->always_toggle_chip_select, data, data_size);
-        self->end_transaction(self->bus);
+        displayio_display_core_begin_transaction(&self->core);
+        self->core.send(self->core.bus, true, self->always_toggle_chip_select, cmd, 1);
+        self->core.send(self->core.bus, false, self->always_toggle_chip_select, data, data_size);
+        displayio_display_core_end_transaction(&self->core);
         uint16_t delay_length_ms = 0;
         if (delay) {
             data_size++;
@@ -291,87 +161,17 @@ STATIC void send_command_sequence(displayio_epaperdisplay_obj_t* self, bool shou
     }
 }
 
-void displayio_epaperdisplay_set_region_to_update(displayio_epaperdisplay_obj_t* self, displayio_area_t* area) {
-    if (self->set_row_window_command == NO_COMMAND) {
-        return;
-    }
-    uint16_t x1 = area->x1;
-    uint16_t x2 = area->x2;
-    uint16_t y1 = area->y1;
-    uint16_t y2 = area->y2;
-    // Collapse down the dimension where multiple pixels are in a byte.
-    uint8_t pixels_per_byte = 8 / self->colorspace.depth;
-    x1 /= pixels_per_byte * self->colorspace.bytes_per_cell;
-    x2 /= pixels_per_byte * self->colorspace.bytes_per_cell;
-
-
-    // Set column.
-    uint8_t data[5];
-    data[0] = self->set_column_window_command;
-    self->send(self->bus, true, self->always_toggle_chip_select, data, 1);
-    uint8_t data_length = 0;
-    if (self->ram_width / pixels_per_byte < 0x100) {
-        data[data_length++] = x1 + self->colstart;
-        data[data_length++] = x2 - 1 + self->colstart;
-    } else {
-        x1 += self->colstart;
-        x2 += self->colstart - 1;
-        data[data_length++] = x1 >> 8;
-        data[data_length++] = x1 & 0xff;
-        data[data_length++] = x2 >> 8;
-        data[data_length++] = x2 & 0xff;
-    }
-    self->send(self->bus, false, self->always_toggle_chip_select, data, data_length);
-    if (self->set_current_column_command != NO_COMMAND) {
-        uint8_t command = self->set_current_column_command;
-        self->send(self->bus, true, self->always_toggle_chip_select, &command, 1);
-        self->send(self->bus, false, self->always_toggle_chip_select, data, data_length / 2);
-    }
-
-    // Set row.
-    data[0] = self->set_row_window_command;
-    self->send(self->bus, true, self->always_toggle_chip_select, data, 1);
-    data_length = 0;
-    if (self->ram_height < 0x100) {
-        data[data_length++] = y1 + self->rowstart;
-        data[data_length++] = y2 - 1 + self->rowstart;
-    } else {
-        y1 += self->rowstart;
-        y2 += self->rowstart - 1;
-        data[data_length++] = y1 & 0xff;
-        data[data_length++] = y1 >> 8;
-        data[data_length++] = y2 & 0xff;
-        data[data_length++] = y2 >> 8;
-    }
-    self->send(self->bus, false, self->always_toggle_chip_select, data, data_length);
-    if (self->set_current_row_command != NO_COMMAND) {
-        uint8_t command = self->set_current_row_command;
-        self->send(self->bus, true, self->always_toggle_chip_select, &command, 1);
-        self->send(self->bus, false, self->always_toggle_chip_select, data, data_length / 2);
-    }
-}
-
 void displayio_epaperdisplay_start_refresh(displayio_epaperdisplay_obj_t* self) {
     // run start sequence
-    self->bus_reset(self->bus);
+    self->core.bus_reset(self->core.bus);
 
     send_command_sequence(self, true, self->start_sequence, self->start_sequence_len);
-    self->last_refresh = ticks_ms;
-}
-
-void displayio_epaperdisplay_background_task(displayio_epaperdisplay_obj_t* self) {
-    if (self->refreshing && self->busy.base.type == &digitalio_digitalinout_type) {
-        if (common_hal_digitalio_digitalinout_get_value(&self->busy) != self->busy_state) {
-            self->refreshing = false;
-            // Run stop sequence but don't wait for busy because busy is set when sleeping.
-            send_command_sequence(self, false, self->stop_sequence, self->stop_sequence_len);
-        }
-    }
+    displayio_display_core_start_refresh(&self->core);
 }
 
 uint32_t common_hal_displayio_epaperdisplay_get_time_to_refresh(displayio_epaperdisplay_obj_t* self) {
     // Refresh at seconds per frame rate.
-    uint32_t elapsed_time = ticks_ms - self->last_refresh;
+    uint32_t elapsed_time = ticks_ms - self->core.last_refresh;
     if (elapsed_time > self->milliseconds_per_frame) {
         return 0;
     }
@@ -380,20 +180,16 @@ uint32_t common_hal_displayio_epaperdisplay_get_time_to_refresh(displayio_epaper
 
 void displayio_epaperdisplay_finish_refresh(displayio_epaperdisplay_obj_t* self) {
     // Actually refresh the display now that all pixel RAM has been updated.
-    displayio_epaperdisplay_begin_transaction(self);
-    self->send(self->bus, true, self->always_toggle_chip_select, &self->refresh_display_command, 1);
-    displayio_epaperdisplay_end_transaction(self);
+    displayio_display_core_begin_transaction(&self->core);
+    self->core.send(self->core.bus, true, self->always_toggle_chip_select, &self->refresh_display_command, 1);
+    displayio_display_core_end_transaction(&self->core);
     self->refreshing = true;
 
-    if (self->current_group != NULL) {
-        displayio_group_finish_refresh(self->current_group);
-    }
-    self->refresh = false;
-    self->full_refresh = false;
-    self->last_refresh = ticks_ms;
+    displayio_display_core_finish_refresh(&self->core);
 }
 
-void displayio_epaperdisplay_send_pixels(displayio_epaperdisplay_obj_t* self, uint8_t* pixels, uint32_t length) {
+mp_obj_t common_hal_displayio_epaperdisplay_get_bus(displayio_epaperdisplay_obj_t* self) {
+    return self->core.bus;
 }
 
 bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, const displayio_area_t* area) {
@@ -401,12 +197,12 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
 
     displayio_area_t clipped;
     // Clip the area to the display by overlapping the areas. If there is no overlap then we're done.
-    if (!displayio_epaperdisplay_clip_area(self, area, &clipped)) {
+    if (!displayio_display_core_clip_area(&self->core, area, &clipped)) {
         return true;
     }
     uint16_t subrectangles = 1;
     uint16_t rows_per_buffer = displayio_area_height(&clipped);
-    uint8_t pixels_per_word = (sizeof(uint32_t) * 8) / self->colorspace.depth;
+    uint8_t pixels_per_word = (sizeof(uint32_t) * 8) / self->core.colorspace.depth;
     uint16_t pixels_per_buffer = displayio_area_size(&clipped);
     if (displayio_area_size(&clipped) > buffer_size * pixels_per_word) {
         rows_per_buffer = buffer_size * pixels_per_word / displayio_area_width(&clipped);
@@ -431,23 +227,23 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
     uint32_t mask[mask_length];
 
     uint8_t passes = 1;
-    if (self->colorspace.tricolor) {
+    if (self->core.colorspace.tricolor) {
         passes = 2;
     }
     for (uint8_t pass = 0; pass < passes; pass++) {
         uint16_t remaining_rows = displayio_area_height(&clipped);
 
-        displayio_epaperdisplay_begin_transaction(self);
-        displayio_epaperdisplay_set_region_to_update(self, &clipped);
-        displayio_epaperdisplay_end_transaction(self);
+        if (self->set_row_window_command != NO_COMMAND) {
+            displayio_display_core_set_region_to_update(&self->core, self->set_column_window_command, self->set_row_window_command, self->set_current_column_command, self->set_current_row_command, false, self->always_toggle_chip_select, &clipped);
+        }
 
         uint8_t write_command = self->write_black_ram_command;
         if (pass == 1) {
             write_command = self->write_color_ram_command;
         }
-        displayio_epaperdisplay_begin_transaction(self);
-        self->send(self->bus, true, self->always_toggle_chip_select, &write_command, 1);
-        displayio_epaperdisplay_end_transaction(self);
+        displayio_display_core_begin_transaction(&self->core);
+        self->core.send(self->core.bus, true, self->always_toggle_chip_select, &write_command, 1);
+        displayio_display_core_end_transaction(&self->core);
 
         for (uint16_t j = 0; j < subrectangles; j++) {
             displayio_area_t subrectangle = {
@@ -462,7 +258,7 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
             remaining_rows -= rows_per_buffer;
 
 
-            uint16_t subrectangle_size_bytes = displayio_area_size(&subrectangle) / (8 / self->colorspace.depth);
+            uint16_t subrectangle_size_bytes = displayio_area_size(&subrectangle) / (8 / self->core.colorspace.depth);
 
             for (uint16_t k = 0; k < mask_length; k++) {
                 mask[k] = 0x00000000;
@@ -471,11 +267,11 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
                 buffer[k] = 0x00000000;
             }
 
-            self->colorspace.grayscale = true;
+            self->core.colorspace.grayscale = true;
             if (pass == 1) {
-                self->colorspace.grayscale = false;
+                self->core.colorspace.grayscale = false;
             }
-            displayio_group_fill_area(self->current_group, &self->colorspace, &subrectangle, mask, buffer);
+            displayio_display_core_fill_area(&self->core, &subrectangle, mask, buffer);
 
             // Invert it all.
             if ((pass == 1 && self->color_bits_inverted) ||
@@ -485,12 +281,12 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
                 }
             }
 
-            if (!displayio_epaperdisplay_begin_transaction(self)) {
+            if (!displayio_display_core_begin_transaction(&self->core)) {
                 // Can't acquire display bus; skip the rest of the data. Try next display.
                 return false;
             }
-            self->send(self->bus, false, self->always_toggle_chip_select, (uint8_t*) buffer, subrectangle_size_bytes);
-            displayio_epaperdisplay_end_transaction(self);
+            self->core.send(self->core.bus, false, self->always_toggle_chip_select, (uint8_t*) buffer, subrectangle_size_bytes);
+            displayio_display_core_end_transaction(&self->core);
 
             // TODO(tannewt): Make refresh displays faster so we don't starve other
             // background tasks.
@@ -512,57 +308,47 @@ bool common_hal_displayio_epaperdisplay_refresh(displayio_epaperdisplay_obj_t* s
             return false;
         }
     }
-    if (self->current_group == NULL) {
-        return false;
+    if (self->core.current_group == NULL) {
+        return true;
     }
     // Refresh at seconds per frame rate.
-    if (ticks_ms - self->last_refresh) > self->milliseconds_per_frame;
-
-    if (displayio_epaperdisplay_get_time_to_refresh(display) > 0) {
+    if (common_hal_displayio_epaperdisplay_get_time_to_refresh(self) > 0) {
         return false;
     }
-    if (!displayio_epaperdisplay_bus_free(display)) {
+    if (!displayio_display_core_bus_free(&self->core)) {
         // Can't acquire display bus; skip updating this display. Try next display.
-        continue;
+        return false;
     }
-    const displayio_area_t* current_area = displayio_epaperdisplay_get_refresh_areas(display);
+    const displayio_area_t* current_area = displayio_epaperdisplay_get_refresh_areas(self);
     if (current_area == NULL) {
-        continue;
+        return true;
     }
-    displayio_epaperdisplay_start_refresh(display);
+    displayio_epaperdisplay_start_refresh(self);
     while (current_area != NULL) {
-        displayio_epaperdisplay_refresh_area(display, current_area);
+        displayio_epaperdisplay_refresh_area(self, current_area);
         current_area = current_area->next;
     }
-    displayio_epaperdisplay_finish_refresh(display);
+    displayio_epaperdisplay_finish_refresh(self);
+    return true;
 }
 
-void release_epaperdisplay(displayio_epaperdisplay_obj_t* self) {
-    if (self->current_group != NULL) {
-        self->current_group->in_group = false;
+void displayio_epaperdisplay_background(displayio_epaperdisplay_obj_t* self) {
+    if (self->refreshing && self->busy.base.type == &digitalio_digitalinout_type) {
+        if (common_hal_digitalio_digitalinout_get_value(&self->busy) != self->busy_state) {
+            self->refreshing = false;
+            // Run stop sequence but don't wait for busy because busy is set when sleeping.
+            send_command_sequence(self, false, self->stop_sequence, self->stop_sequence_len);
+        }
     }
+}
+
+void release_epaperdisplay(displayio_epaperdisplay_obj_t* self) {
+    release_display_core(&self->core);
     if (self->busy.base.type == &digitalio_digitalinout_type) {
         common_hal_digitalio_digitalinout_deinit(&self->busy);
     }
 }
 
-bool displayio_epaperdisplay_fill_area(displayio_epaperdisplay_obj_t *self, displayio_area_t* area, uint32_t* mask, uint32_t *buffer) {
-    return displayio_group_fill_area(self->current_group, &self->colorspace, area, mask, buffer);
-}
-
-bool displayio_epaperdisplay_clip_area(displayio_epaperdisplay_obj_t *self, const displayio_area_t* area, displayio_area_t* clipped) {
-    bool overlaps = displayio_area_compute_overlap(&self->area, area, clipped);
-    if (!overlaps) {
-        return false;
-    }
-    // Expand the area if we have multiple pixels per byte and we need to byte
-    // align the bounds.
-    uint8_t pixels_per_byte = 8;
-    if (clipped->x1 % pixels_per_byte != 0) {
-        clipped->x1 -= clipped->x1 % pixels_per_byte;
-    }
-    if (clipped->x2 % pixels_per_byte != 0) {
-        clipped->x2 += pixels_per_byte - clipped->x2 % pixels_per_byte;
-    }
-    return true;
+void displayio_epaperdisplay_collect_ptrs(displayio_epaperdisplay_obj_t* self) {
+    displayio_display_core_collect_ptrs(&self->core);
 }
diff --git a/shared-module/displayio/EPaperDisplay.h b/shared-module/displayio/EPaperDisplay.h
index cc7db6f6d..88b5ebfaf 100644
--- a/shared-module/displayio/EPaperDisplay.h
+++ b/shared-module/displayio/EPaperDisplay.h
@@ -32,38 +32,17 @@
 #include "shared-bindings/pulseio/PWMOut.h"
 
 #include "shared-module/displayio/area.h"
-
-typedef void (*display_bus_bus_reset)(mp_obj_t bus);
-typedef bool (*display_bus_bus_free)(mp_obj_t bus);
-typedef bool (*display_bus_begin_transaction)(mp_obj_t bus);
-typedef void (*display_bus_send)(mp_obj_t bus, bool command, bool toggle_every_byte, uint8_t *data, uint32_t data_length);
-typedef void (*display_bus_end_transaction)(mp_obj_t bus);
+#include "shared-module/displayio/display_core.h"
 
 typedef struct {
     mp_obj_base_t base;
-    mp_obj_t bus;
-    displayio_group_t *current_group;
-    uint64_t last_refresh;
-    display_bus_bus_reset bus_reset;
-    display_bus_bus_free bus_free;
-    display_bus_begin_transaction begin_transaction;
-    display_bus_send send;
-    display_bus_end_transaction end_transaction;
+    displayio_display_core_t core;
     digitalio_digitalinout_obj_t busy;
     uint32_t milliseconds_per_frame;
     uint8_t* start_sequence;
     uint32_t start_sequence_len;
     uint8_t* stop_sequence;
     uint32_t stop_sequence_len;
-    displayio_buffer_transform_t transform;
-    displayio_area_t area;
-    uint16_t width;
-    uint16_t height;
-    uint16_t ram_width;
-    uint16_t ram_height;
-    _displayio_colorspace_t colorspace;
-    int16_t colstart;
-    int16_t rowstart;
     uint16_t set_column_window_command;
     uint16_t set_row_window_command;
     uint16_t set_current_column_command;
@@ -76,11 +55,12 @@ typedef struct {
     bool black_bits_inverted;
     bool color_bits_inverted;
     bool refreshing;
-    bool full_refresh; // New group means we need to refresh the whole display.
     bool always_toggle_chip_select;
 } displayio_epaperdisplay_obj_t;
 
 void displayio_epaperdisplay_background(displayio_epaperdisplay_obj_t* self);
 void release_epaperdisplay(displayio_epaperdisplay_obj_t* self);
 
+void displayio_epaperdisplay_collect_ptrs(displayio_epaperdisplay_obj_t* self);
+
 #endif // MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_EPAPERDISPLAY_H
diff --git a/shared-module/displayio/__init__.c b/shared-module/displayio/__init__.c
index 0ebed58c2..0a3b1fd10 100644
--- a/shared-module/displayio/__init__.c
+++ b/shared-module/displayio/__init__.c
@@ -4,7 +4,6 @@
 #include "shared-module/displayio/__init__.h"
 
 #include "lib/utils/interrupt_char.h"
-#include "py/gc.h"
 #include "py/reload.h"
 #include "py/runtime.h"
 #include "shared-bindings/board/__init__.h"
@@ -16,7 +15,6 @@
 #include "supervisor/shared/autoreload.h"
 #include "supervisor/shared/display.h"
 #include "supervisor/memory.h"
-#include "supervisor/usb.h"
 
 primary_display_t displays[CIRCUITPY_DISPLAY_LIMIT];
 
@@ -46,8 +44,8 @@ void displayio_background(void) {
         }
         if (displays[i].display.base.type == &displayio_display_type) {
             displayio_display_background(&displays[i].display);
-        } else if (displays[i].epaperdisplay.base.type == &displayio_epaperdisplay_type) {
-            displayio_epaperdisplay_background(&displays[i].epaperdisplay);
+        } else if (displays[i].epaper_display.base.type == &displayio_epaperdisplay_type) {
+            displayio_epaperdisplay_background(&displays[i].epaper_display);
         }
     }
 
@@ -162,9 +160,9 @@ void displayio_gc_collect(void) {
         // Alternatively, we could use gc_collect_root over the whole object,
         // but this is more precise, and is the only field that needs marking.
         if (displays[i].display.base.type == &displayio_display_type) {
-            gc_collect_ptr(displays[i].display.current_group);
+            displayio_display_collect_ptrs(&displays[i].display);
         } else if (displays[i].epaper_display.base.type == &displayio_epaperdisplay_type) {
-            gc_collect_ptr(displays[i].epaper_display.current_group);
+            displayio_epaperdisplay_collect_ptrs(&displays[i].epaper_display);
         }
     }
 }
diff --git a/shared-module/displayio/display_core.c b/shared-module/displayio/display_core.c
new file mode 100644
index 000000000..f8a8d8fea
--- /dev/null
+++ b/shared-module/displayio/display_core.c
@@ -0,0 +1,309 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Scott Shawcroft for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "shared-bindings/displayio/Display.h"
+
+#include "py/gc.h"
+#include "py/runtime.h"
+#include "shared-bindings/displayio/FourWire.h"
+#include "shared-bindings/displayio/I2CDisplay.h"
+#include "shared-bindings/displayio/ParallelBus.h"
+#include "shared-bindings/microcontroller/Pin.h"
+#include "shared-bindings/time/__init__.h"
+#include "shared-module/displayio/__init__.h"
+#include "supervisor/shared/display.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#include "tick.h"
+
+void displayio_display_core_construct(displayio_display_core_t* self,
+        mp_obj_t bus, uint16_t width, uint16_t height, uint16_t ram_width, uint16_t ram_height, int16_t colstart, int16_t rowstart, uint16_t rotation,
+        uint16_t color_depth, bool grayscale, bool pixels_in_byte_share_row, uint8_t bytes_per_cell, bool reverse_pixels_in_byte) {
+    self->colorspace.depth = color_depth;
+    self->colorspace.grayscale = grayscale;
+    self->colorspace.pixels_in_byte_share_row = pixels_in_byte_share_row;
+    self->colorspace.bytes_per_cell = bytes_per_cell;
+    self->colorspace.reverse_pixels_in_byte = reverse_pixels_in_byte;
+    self->current_group = NULL;
+    self->colstart = colstart;
+    self->rowstart = rowstart;
+
+    if (MP_OBJ_IS_TYPE(bus, &displayio_parallelbus_type)) {
+        self->bus_reset = common_hal_displayio_parallelbus_reset;
+        self->bus_free = common_hal_displayio_parallelbus_bus_free;
+        self->begin_transaction = common_hal_displayio_parallelbus_begin_transaction;
+        self->send = common_hal_displayio_parallelbus_send;
+        self->end_transaction = common_hal_displayio_parallelbus_end_transaction;
+    } else if (MP_OBJ_IS_TYPE(bus, &displayio_fourwire_type)) {
+        self->bus_reset = common_hal_displayio_fourwire_reset;
+        self->bus_free = common_hal_displayio_fourwire_bus_free;
+        self->begin_transaction = common_hal_displayio_fourwire_begin_transaction;
+        self->send = common_hal_displayio_fourwire_send;
+        self->end_transaction = common_hal_displayio_fourwire_end_transaction;
+    } else if (MP_OBJ_IS_TYPE(bus, &displayio_i2cdisplay_type)) {
+        self->bus_reset = common_hal_displayio_i2cdisplay_reset;
+        self->bus_free = common_hal_displayio_i2cdisplay_bus_free;
+        self->begin_transaction = common_hal_displayio_i2cdisplay_begin_transaction;
+        self->send = common_hal_displayio_i2cdisplay_send;
+        self->end_transaction = common_hal_displayio_i2cdisplay_end_transaction;
+    } else {
+        mp_raise_ValueError(translate("Unsupported display bus type"));
+    }
+    self->bus = bus;
+
+
+    supervisor_start_terminal(width, height);
+
+    self->width = width;
+    self->height = height;
+    self->ram_width = width;
+    self->ram_height = height;
+    rotation = rotation % 360;
+    self->transform.x = 0;
+    self->transform.y = 0;
+    self->transform.scale = 1;
+    self->transform.mirror_x = false;
+    self->transform.mirror_y = false;
+    self->transform.transpose_xy = false;
+    if (rotation == 0 || rotation == 180) {
+        if (rotation == 180) {
+            self->transform.mirror_x = true;
+            self->transform.mirror_y = true;
+        }
+    } else {
+        self->transform.transpose_xy = true;
+        if (rotation == 270) {
+            self->transform.mirror_y = true;
+        } else {
+            self->transform.mirror_x = true;
+        }
+    }
+
+    self->area.x1 = 0;
+    self->area.y1 = 0;
+    self->area.next = NULL;
+
+    self->transform.dx = 1;
+    self->transform.dy = 1;
+    if (self->transform.transpose_xy) {
+        self->area.x2 = height;
+        self->area.y2 = width;
+        if (self->transform.mirror_x) {
+            self->transform.x = height;
+            self->transform.dx = -1;
+        }
+        if (self->transform.mirror_y) {
+            self->transform.y = width;
+            self->transform.dy = -1;
+        }
+    } else {
+        self->area.x2 = width;
+        self->area.y2 = height;
+        if (self->transform.mirror_x) {
+            self->transform.x = width;
+            self->transform.dx = -1;
+        }
+        if (self->transform.mirror_y) {
+            self->transform.y = height;
+            self->transform.dy = -1;
+        }
+    }
+}
+
+bool displayio_display_core_show(displayio_display_core_t* self, displayio_group_t* root_group) {
+    if (root_group == NULL) {
+        if (!circuitpython_splash.in_group) {
+            root_group = &circuitpython_splash;
+        } else if (self->current_group == &circuitpython_splash) {
+            return false;
+        }
+    }
+    if (root_group == self->current_group) {
+        return true;
+    }
+    if (root_group != NULL && root_group->in_group) {
+        return false;
+    }
+    if (self->current_group != NULL) {
+        self->current_group->in_group = false;
+    }
+
+    if (root_group != NULL) {
+        displayio_group_update_transform(root_group, &self->transform);
+        root_group->in_group = true;
+    }
+    self->current_group = root_group;
+    self->full_refresh = true;
+    return true;
+}
+
+uint16_t displayio_display_core_get_width(displayio_display_core_t* self){
+    return self->width;
+}
+
+uint16_t displayio_display_core_get_height(displayio_display_core_t* self){
+    return self->height;
+}
+
+bool displayio_display_core_bus_free(displayio_display_core_t *self) {
+    return self->bus_free(self->bus);
+}
+
+bool displayio_display_core_begin_transaction(displayio_display_core_t* self) {
+    return self->begin_transaction(self->bus);
+}
+
+void displayio_display_core_end_transaction(displayio_display_core_t* self) {
+    self->end_transaction(self->bus);
+}
+
+void displayio_display_core_set_region_to_update(displayio_display_core_t* self, uint8_t column_command, uint8_t row_command, uint16_t set_current_column_command, uint16_t set_current_row_command, bool data_as_commands, bool always_toggle_chip_select, displayio_area_t* area) {
+    displayio_display_core_begin_transaction(self);
+    uint16_t x1 = area->x1;
+    uint16_t x2 = area->x2;
+    uint16_t y1 = area->y1;
+    uint16_t y2 = area->y2;
+    // Collapse down the dimension where multiple pixels are in a byte.
+    if (self->colorspace.depth < 8) {
+        uint8_t pixels_per_byte = 8 / self->colorspace.depth;
+        if (self->colorspace.pixels_in_byte_share_row) {
+            x1 /= pixels_per_byte * self->colorspace.bytes_per_cell;
+            x2 /= pixels_per_byte * self->colorspace.bytes_per_cell;
+        } else {
+            y1 /= pixels_per_byte * self->colorspace.bytes_per_cell;
+            y2 /= pixels_per_byte * self->colorspace.bytes_per_cell;
+        }
+    }
+
+    // Set column.
+    uint8_t data[5];
+    data[0] = column_command;
+    uint8_t data_length = 1;
+    if (!data_as_commands) {
+        self->send(self->bus, true, true, data, 1);
+        data_length = 0;
+    }
+    if (self->ram_width < 0x100) {
+        data[data_length++] = x1 + self->colstart;
+        data[data_length++] = x2 - 1 + self->colstart;
+    } else {
+        x1 += self->colstart;
+        x2 += self->colstart - 1;
+        data[data_length++] = x1 >> 8;
+        data[data_length++] = x1 & 0xff;
+        data[data_length++] = x2 >> 8;
+        data[data_length++] = x2 & 0xff;
+    }
+    self->send(self->bus, data_as_commands, data_as_commands, data, data_length);
+    if (set_current_column_command != NO_COMMAND) {
+        uint8_t command = set_current_column_command;
+        self->send(self->bus, true, always_toggle_chip_select, &command, 1);
+        self->send(self->bus, false, always_toggle_chip_select, data, data_length / 2);
+    }
+
+    // Set row.
+    data[0] = row_command;
+    data_length = 1;
+    if (!data_as_commands) {
+        self->send(self->bus, true, true, data, 1);
+        data_length = 0;
+    }
+    if (self->ram_height < 0x100) {
+        data[data_length++] = y1 + self->rowstart;
+        data[data_length++] = y2 - 1 + self->rowstart;
+    } else {
+        y1 += self->rowstart;
+        y2 += self->rowstart - 1;
+        data[data_length++] = y1 >> 8;
+        data[data_length++] = y1 & 0xff;
+        data[data_length++] = y2 >> 8;
+        data[data_length++] = y2 & 0xff;
+    }
+    self->send(self->bus, data_as_commands, data_as_commands, data, data_length);
+    if (set_current_row_command != NO_COMMAND) {
+        uint8_t command = set_current_row_command;
+        self->send(self->bus, true, always_toggle_chip_select, &command, 1);
+        self->send(self->bus, false, always_toggle_chip_select, data, data_length / 2);
+    }
+
+    displayio_display_core_end_transaction(self);
+}
+
+void displayio_display_core_start_refresh(displayio_display_core_t* self) {
+    self->last_refresh = ticks_ms;
+}
+
+void displayio_display_core_finish_refresh(displayio_display_core_t* self) {
+    if (self->current_group != NULL) {
+        displayio_group_finish_refresh(self->current_group);
+    }
+    self->full_refresh = false;
+    self->last_refresh = ticks_ms;
+}
+
+void release_display_core(displayio_display_core_t* self) {
+    if (self->current_group != NULL) {
+        self->current_group->in_group = false;
+    }
+}
+
+void displayio_display_core_collect_ptrs(displayio_display_core_t* self) {
+    gc_collect_ptr(self->current_group);
+}
+
+bool displayio_display_core_fill_area(displayio_display_core_t *self, displayio_area_t* area, uint32_t* mask, uint32_t *buffer) {
+    return displayio_group_fill_area(self->current_group, &self->colorspace, area, mask, buffer);
+}
+
+bool displayio_display_core_clip_area(displayio_display_core_t *self, const displayio_area_t* area, displayio_area_t* clipped) {
+    bool overlaps = displayio_area_compute_overlap(&self->area, area, clipped);
+    if (!overlaps) {
+        return false;
+    }
+    // Expand the area if we have multiple pixels per byte and we need to byte
+    // align the bounds.
+    if (self->colorspace.depth < 8) {
+        uint8_t pixels_per_byte = 8 / self->colorspace.depth * self->colorspace.bytes_per_cell;
+        if (self->colorspace.pixels_in_byte_share_row) {
+            if (clipped->x1 % pixels_per_byte != 0) {
+                clipped->x1 -= clipped->x1 % pixels_per_byte;
+            }
+            if (clipped->x2 % pixels_per_byte != 0) {
+                clipped->x2 += pixels_per_byte - clipped->x2 % pixels_per_byte;
+            }
+        } else {
+            if (clipped->y1 % pixels_per_byte != 0) {
+                clipped->y1 -= clipped->y1 % pixels_per_byte;
+            }
+            if (clipped->y2 % pixels_per_byte != 0) {
+                clipped->y2 += pixels_per_byte - clipped->y2 % pixels_per_byte;
+            }
+        }
+    }
+    return true;
+}
diff --git a/shared-module/displayio/display_core.h b/shared-module/displayio/display_core.h
new file mode 100644
index 000000000..c837ce913
--- /dev/null
+++ b/shared-module/displayio/display_core.h
@@ -0,0 +1,90 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Scott Shawcroft for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_DISPLAY_CORE_H
+#define MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_DISPLAY_CORE_H
+
+#include "shared-bindings/displayio/Group.h"
+
+#include "shared-module/displayio/area.h"
+
+#define NO_COMMAND 0x100
+
+typedef void (*display_bus_bus_reset)(mp_obj_t bus);
+typedef bool (*display_bus_bus_free)(mp_obj_t bus);
+typedef bool (*display_bus_begin_transaction)(mp_obj_t bus);
+typedef void (*display_bus_send)(mp_obj_t bus, bool command, bool toggle_every_byte, uint8_t *data, uint32_t data_length);
+typedef void (*display_bus_end_transaction)(mp_obj_t bus);
+
+typedef struct {
+    mp_obj_t bus;
+    displayio_group_t *current_group;
+    uint64_t last_refresh;
+    display_bus_bus_reset bus_reset;
+    display_bus_bus_free bus_free;
+    display_bus_begin_transaction begin_transaction;
+    display_bus_send send;
+    display_bus_end_transaction end_transaction;
+    displayio_buffer_transform_t transform;
+    displayio_area_t area;
+    uint16_t width;
+    uint16_t height;
+    uint16_t rotation;
+    uint16_t ram_width;
+    uint16_t ram_height;
+    _displayio_colorspace_t colorspace;
+    int16_t colstart;
+    int16_t rowstart;
+    bool full_refresh; // New group means we need to refresh the whole display.
+} displayio_display_core_t;
+
+void displayio_display_core_construct(displayio_display_core_t* self,
+        mp_obj_t bus, uint16_t width, uint16_t height, uint16_t ram_width, uint16_t ram_height, int16_t colstart, int16_t rowstart, uint16_t rotation,
+        uint16_t color_depth, bool grayscale, bool pixels_in_byte_share_row, uint8_t bytes_per_cell, bool reverse_pixels_in_byte);
+
+bool displayio_display_core_show(displayio_display_core_t* self, displayio_group_t* root_group);
+
+uint16_t displayio_display_core_get_width(displayio_display_core_t* self);
+uint16_t displayio_display_core_get_height(displayio_display_core_t* self);
+
+bool displayio_display_core_bus_free(displayio_display_core_t *self);
+bool displayio_display_core_begin_transaction(displayio_display_core_t* self);
+void displayio_display_core_end_transaction(displayio_display_core_t* self);
+
+void displayio_display_core_set_region_to_update(displayio_display_core_t* self, uint8_t column_command, uint8_t row_command, uint16_t set_current_column_command, uint16_t set_current_row_command, bool data_as_commands, bool always_toggle_chip_select, displayio_area_t* area);
+
+void release_display_core(displayio_display_core_t* self);
+
+void displayio_display_core_start_refresh(displayio_display_core_t* self);
+void displayio_display_core_finish_refresh(displayio_display_core_t* self);
+
+void displayio_display_core_collect_ptrs(displayio_display_core_t* self);
+
+bool displayio_display_core_fill_area(displayio_display_core_t *self, displayio_area_t* area, uint32_t* mask, uint32_t *buffer);
+
+bool displayio_display_core_clip_area(displayio_display_core_t *self, const displayio_area_t* area, displayio_area_t* clipped);
+
+#endif // MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO_DISPLAY_CORE_H