Add grayscale EInk support

5 files changed, 18 insertions, 9 deletions

diff --git a/shared-module/displayio/ColorConverter.c b/shared-module/displayio/ColorConverter.c
index dc64da03d..03ec99ceb 100644
--- a/shared-module/displayio/ColorConverter.c
+++ b/shared-module/displayio/ColorConverter.c
@@ -165,9 +165,9 @@ void displayio_colorconverter_convert(displayio_colorconverter_t *self, const _d
             g8 = MIN(255,g8 + (randg&0x03));
         } else {
             int bitmask = 0xFF >> colorspace->depth;
-            b8 = MIN(255,b8 + (randb&bitmask));
-            r8 = MIN(255,r8 + (randr&bitmask));
-            g8 = MIN(255,g8 + (randg&bitmask));
+            b8 = MIN(255,b8 + (randb & bitmask));
+            r8 = MIN(255,r8 + (randr & bitmask));
+            g8 = MIN(255,g8 + (randg & bitmask));
         }
         pixel = r8 << 16 | g8 << 8 | b8;
     }
@@ -196,7 +196,8 @@ void displayio_colorconverter_convert(displayio_colorconverter_t *self, const _d
         return;
     }  else if (colorspace->grayscale && colorspace->depth <= 8) {
         uint8_t luma = displayio_colorconverter_compute_luma(pixel);
-        output_color->pixel = luma >> (8 - colorspace->depth);
+        size_t bitmask = (1 << colorspace->depth) - 1;
+        output_color->pixel = (luma >> colorspace->grayscale_bit) & bitmask;
         output_color->opaque = true;
         return;
     }
diff --git a/shared-module/displayio/EPaperDisplay.c b/shared-module/displayio/EPaperDisplay.c
index 46c7ea82e..514b99a13 100644
--- a/shared-module/displayio/EPaperDisplay.c
+++ b/shared-module/displayio/EPaperDisplay.c
@@ -49,7 +49,7 @@ void common_hal_displayio_epaperdisplay_construct(displayio_epaperdisplay_obj_t*
         uint16_t set_column_window_command, uint16_t set_row_window_command,
         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, mp_float_t refresh_time,
-        const mcu_pin_obj_t* busy_pin, bool busy_state, mp_float_t seconds_per_frame, bool chip_select) {
+        const mcu_pin_obj_t* busy_pin, bool busy_state, mp_float_t seconds_per_frame, bool chip_select, bool grayscale) {
     if (highlight_color != 0x000000) {
         self->core.colorspace.tricolor = true;
         self->core.colorspace.tricolor_hue = displayio_colorconverter_compute_hue(highlight_color);
@@ -72,6 +72,7 @@ void common_hal_displayio_epaperdisplay_construct(displayio_epaperdisplay_obj_t*
     self->refreshing = false;
     self->milliseconds_per_frame = seconds_per_frame * 1000;
     self->chip_select = chip_select ? CHIP_SELECT_TOGGLE_EVERY_BYTE : CHIP_SELECT_UNTOUCHED;
+    self->grayscale = grayscale;
 
     self->start_sequence = start_sequence;
     self->start_sequence_len = start_sequence_len;
@@ -230,17 +231,16 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
     uint32_t mask[mask_length];
 
     uint8_t passes = 1;
-    if (self->core.colorspace.tricolor) {
+    if (self->core.colorspace.tricolor || self->grayscale) {
         passes = 2;
     }
     for (uint8_t pass = 0; pass < passes; pass++) {
         uint16_t remaining_rows = displayio_area_height(&clipped);
 
-        // added false parameter at end for SH1107_addressing quirk
         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->chip_select, &clipped, false);
+            false, self->chip_select, &clipped, false /* SH1107_addressing */);
         }
 
         uint8_t write_command = self->write_black_ram_command;
@@ -270,8 +270,13 @@ bool displayio_epaperdisplay_refresh_area(displayio_epaperdisplay_obj_t* self, c
             memset(buffer, 0, buffer_size * sizeof(buffer[0]));
 
             self->core.colorspace.grayscale = true;
+            self->core.colorspace.grayscale_bit = 7;
             if (pass == 1) {
-                self->core.colorspace.grayscale = false;
+                if (self->grayscale) { // 4-color grayscale
+                    self->core.colorspace.grayscale_bit = 6;
+                } else { // Tri-color
+                    self->core.colorspace.grayscale = false;
+                }
             }
             displayio_display_core_fill_area(&self->core, &subrectangle, mask, buffer);
 
diff --git a/shared-module/displayio/EPaperDisplay.h b/shared-module/displayio/EPaperDisplay.h
index 3b9f6e368..4103fe5fc 100644
--- a/shared-module/displayio/EPaperDisplay.h
+++ b/shared-module/displayio/EPaperDisplay.h
@@ -55,6 +55,7 @@ typedef struct {
     bool black_bits_inverted;
     bool color_bits_inverted;
     bool refreshing;
+    bool grayscale;
     display_chip_select_behavior_t chip_select;
 } displayio_epaperdisplay_obj_t;
 
diff --git a/shared-module/displayio/Palette.h b/shared-module/displayio/Palette.h
index da72f250f..993912cc5 100644
--- a/shared-module/displayio/Palette.h
+++ b/shared-module/displayio/Palette.h
@@ -37,6 +37,7 @@ typedef struct {
     uint8_t bytes_per_cell;
     uint8_t tricolor_hue;
     uint8_t tricolor_luma;
+    uint8_t grayscale_bit; // The lowest grayscale bit. Normally 8 - depth.
     bool grayscale;
     bool tricolor;
     bool pixels_in_byte_share_row;
diff --git a/shared-module/displayio/display_core.c b/shared-module/displayio/display_core.c
index 411f9f373..57d33b565 100644
--- a/shared-module/displayio/display_core.c
+++ b/shared-module/displayio/display_core.c
@@ -48,6 +48,7 @@ void displayio_display_core_construct(displayio_display_core_t* self,
         uint16_t color_depth, bool grayscale, bool pixels_in_byte_share_row, uint8_t bytes_per_cell, bool reverse_pixels_in_byte, bool reverse_bytes_in_word) {
     self->colorspace.depth = color_depth;
     self->colorspace.grayscale = grayscale;
+    self->colorspace.grayscale_bit = 8 - color_depth;
     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;