Add support for grayscale displays that are < 8 bit depth.

This also improves Palette so it stores the original RGB888 colors.

Lastly, it adds I2CDisplay as a display bus to talk over I2C. Particularly
useful for the SSD1306.

Fixes #1828. Fixes #1956

12 files changed, 62 insertions, 7 deletions

diff --git a/ports/atmel-samd/boards/hallowing_m0_express/board.c b/ports/atmel-samd/boards/hallowing_m0_express/board.c
index a0e160757..1bbbfbaf8 100644
--- a/ports/atmel-samd/boards/hallowing_m0_express/board.c
+++ b/ports/atmel-samd/boards/hallowing_m0_express/board.c
@@ -91,6 +91,8 @@ void board_init(void) {
         1, // row start
         0, // rotation
         16, // Color depth
+        false, // Grayscale
+        false, // Pixels in a byte share a row. Only used for depth < 8
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
@@ -98,6 +100,7 @@ void board_init(void) {
         display_init_sequence,
         sizeof(display_init_sequence),
         &pin_PA00,
+        0x100, // Brightness command. Only available when <= 0xff
         1.0f, // brightness (ignored)
         true, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/boards/pybadge/board.c b/ports/atmel-samd/boards/pybadge/board.c
index 38902315a..7e6c11dd4 100644
--- a/ports/atmel-samd/boards/pybadge/board.c
+++ b/ports/atmel-samd/boards/pybadge/board.c
@@ -93,6 +93,8 @@ void board_init(void) {
         0, // row start
         270, // rotation
         16, // Color depth
+        false, // grayscale
+        false, // pixels in byte share row. only used for depth < 8
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
@@ -100,6 +102,7 @@ void board_init(void) {
         display_init_sequence,
         sizeof(display_init_sequence),
         &pin_PA01,  // backlight pin
+        0x100, // no brightness command
         1.0f, // brightness (ignored)
         true, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/boards/pybadge_airlift/board.c b/ports/atmel-samd/boards/pybadge_airlift/board.c
index a1f778df1..d7f291d7d 100644
--- a/ports/atmel-samd/boards/pybadge_airlift/board.c
+++ b/ports/atmel-samd/boards/pybadge_airlift/board.c
@@ -71,6 +71,8 @@ void board_init(void) {
         0, // row start
         90, // rotation
         16, // Color depth
+        false, // grayscale
+        false, // pixels in byte share row. Only used for depth < 8
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
@@ -78,6 +80,7 @@ void board_init(void) {
         display_init_sequence,
         sizeof(display_init_sequence),
         &pin_PA01,  // backlight pin
+        0x100, // brightness command, only valid <= 0xff
         1.0f, // brightness (ignored)
         true, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/boards/pygamer/board.c b/ports/atmel-samd/boards/pygamer/board.c
index 7b54b6fb5..e59b7c458 100644
--- a/ports/atmel-samd/boards/pygamer/board.c
+++ b/ports/atmel-samd/boards/pygamer/board.c
@@ -93,6 +93,8 @@ void board_init(void) {
         0, // row start
         270, // rotation
         16, // Color depth
+        false, // Grayscale
+        false, // pixels in a byte share a row. Only valid for depths < 8
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
@@ -100,6 +102,7 @@ void board_init(void) {
         display_init_sequence,
         sizeof(display_init_sequence),
         &pin_PA01,  // backlight pin
+        0x100, // Brightness command. Only available when < 0xff
         1.0f, // brightness (ignored)
         true, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/boards/pygamer_advance/board.c b/ports/atmel-samd/boards/pygamer_advance/board.c
index d1c5edc99..b23353998 100644
--- a/ports/atmel-samd/boards/pygamer_advance/board.c
+++ b/ports/atmel-samd/boards/pygamer_advance/board.c
@@ -71,6 +71,8 @@ void board_init(void) {
         0, // row start
         90, // rotation
         16, // Color depth
+        false, // Grayscale
+        false, // pixels in a byte share a row. Only valid for depths < 8
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
@@ -78,6 +80,7 @@ void board_init(void) {
         display_init_sequence,
         sizeof(display_init_sequence),
         &pin_PA01,  // backlight pin
+        0x100, // Brightness command. Only available when < 0xff
         1.0f, // brightness (ignored)
         true, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/boards/pyportal/board.c b/ports/atmel-samd/boards/pyportal/board.c
index bb80c5b48..7fffb764f 100644
--- a/ports/atmel-samd/boards/pyportal/board.c
+++ b/ports/atmel-samd/boards/pyportal/board.c
@@ -83,13 +83,16 @@ void board_init(void) {
         0, // row start
         0, // rotation
         16, // Color depth
+        false, // grayscale
+        false, // pixels_in_byte_share_row (unused for depths > 8)
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
         0x37, // Set vertical scroll command
         display_init_sequence,
         sizeof(display_init_sequence),
-        &pin_PB31,
+        &pin_PB31, // Backlight pin
+        0x100, // Brightness command > 0xff is none s
         1.0f, // brightness (ignored)
         true, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/boards/ugame10/board.c b/ports/atmel-samd/boards/ugame10/board.c
index 828f0c87d..27a03ad91 100644
--- a/ports/atmel-samd/boards/ugame10/board.c
+++ b/ports/atmel-samd/boards/ugame10/board.c
@@ -91,6 +91,8 @@ void board_init(void) {
         2, // row start
         0, // rotation
         16, // Color depth
+        false, // grayscale
+        false, // pixels in byte share row. Only used with depth < 8
         MIPI_COMMAND_SET_COLUMN_ADDRESS, // Set column command
         MIPI_COMMAND_SET_PAGE_ADDRESS, // Set row command
         MIPI_COMMAND_WRITE_MEMORY_START, // Write memory command
@@ -98,6 +100,7 @@ void board_init(void) {
         display_init_sequence,
         sizeof(display_init_sequence),
         NULL,
+        0x100, // brightness command. Only valid <=0xff
         1.0f, // brightness
         false, // auto_brightness
         false, // single_byte_bounds
diff --git a/ports/atmel-samd/common-hal/busio/I2C.c b/ports/atmel-samd/common-hal/busio/I2C.c
index a0c04d65d..cdc616bbc 100644
--- a/ports/atmel-samd/common-hal/busio/I2C.c
+++ b/ports/atmel-samd/common-hal/busio/I2C.c
@@ -36,6 +36,8 @@
 #include "shared-bindings/microcontroller/__init__.h"
 #include "supervisor/shared/translate.h"
 
+#include "common-hal/busio/SPI.h" // for never_reset_sercom
+
 // Number of times to try to send packet if failed.
 #define ATTEMPTS 2
 
@@ -225,3 +227,10 @@ uint8_t common_hal_busio_i2c_read(busio_i2c_obj_t *self, uint16_t addr,
     }
     return MP_EIO;
 }
+
+void common_hal_busio_i2c_never_reset(busio_i2c_obj_t *self) {
+    never_reset_sercom(self->i2c_desc.device.hw);
+
+    never_reset_pin_number(self->scl_pin);
+    never_reset_pin_number(self->sda_pin);
+}
diff --git a/ports/atmel-samd/common-hal/busio/SPI.h b/ports/atmel-samd/common-hal/busio/SPI.h
index 56d163a9d..a1c0e1517 100644
--- a/ports/atmel-samd/common-hal/busio/SPI.h
+++ b/ports/atmel-samd/common-hal/busio/SPI.h
@@ -43,6 +43,7 @@ typedef struct {
 } busio_spi_obj_t;
 
 void reset_sercoms(void);
+void never_reset_sercom(Sercom* sercom);
 
 
 #endif // MICROPY_INCLUDED_ATMEL_SAMD_COMMON_HAL_BUSIO_SPI_H
diff --git a/ports/atmel-samd/common-hal/displayio/ParallelBus.c b/ports/atmel-samd/common-hal/displayio/ParallelBus.c
index 7a5f61448..c370f7e52 100644
--- a/ports/atmel-samd/common-hal/displayio/ParallelBus.c
+++ b/ports/atmel-samd/common-hal/displayio/ParallelBus.c
@@ -31,6 +31,7 @@
 #include "common-hal/microcontroller/Pin.h"
 #include "py/runtime.h"
 #include "shared-bindings/digitalio/DigitalInOut.h"
+#include "shared-bindings/microcontroller/__init__.h"
 
 #include "tick.h"
 
@@ -66,10 +67,6 @@ void common_hal_displayio_parallelbus_construct(displayio_parallelbus_obj_t* sel
     common_hal_digitalio_digitalinout_construct(&self->chip_select, chip_select);
     common_hal_digitalio_digitalinout_switch_to_output(&self->chip_select, true, DRIVE_MODE_PUSH_PULL);
 
-    self->reset.base.type = &digitalio_digitalinout_type;
-    common_hal_digitalio_digitalinout_construct(&self->reset, reset);
-    common_hal_digitalio_digitalinout_switch_to_output(&self->reset, true, DRIVE_MODE_PUSH_PULL);
-
     self->write.base.type = &digitalio_digitalinout_type;
     common_hal_digitalio_digitalinout_construct(&self->write, write);
     common_hal_digitalio_digitalinout_switch_to_output(&self->write, true, DRIVE_MODE_PUSH_PULL);
@@ -82,11 +79,21 @@ void common_hal_displayio_parallelbus_construct(displayio_parallelbus_obj_t* sel
     self->write_group = &PORT->Group[write->number / 32];
     self->write_mask = 1 << (write->number % 32);
 
+    if (reset != NULL) {
+        self->reset.base.type = &digitalio_digitalinout_type;
+        common_hal_digitalio_digitalinout_construct(&self->reset, reset);
+        common_hal_digitalio_digitalinout_switch_to_output(&self->reset, true, DRIVE_MODE_PUSH_PULL);
+        never_reset_pin_number(reset->number);
+
+        common_hal_digitalio_digitalinout_set_value(&self->reset, false);
+        common_hal_mcu_delay_us(4);
+        common_hal_digitalio_digitalinout_set_value(&self->reset, true);
+    }
+
     never_reset_pin_number(command->number);
     never_reset_pin_number(chip_select->number);
     never_reset_pin_number(write->number);
     never_reset_pin_number(read->number);
-    never_reset_pin_number(reset->number);
     for (uint8_t i = 0; i < 8; i++) {
         never_reset_pin_number(data_pin + i);
     }
diff --git a/ports/nrf/common-hal/busio/I2C.c b/ports/nrf/common-hal/busio/I2C.c
index 538c87f2d..71835d16a 100644
--- a/ports/nrf/common-hal/busio/I2C.c
+++ b/ports/nrf/common-hal/busio/I2C.c
@@ -57,13 +57,30 @@ STATIC twim_peripheral_t twim_peripherals[] = {
 #endif
 };
 
+STATIC bool never_reset[MP_ARRAY_SIZE(twim_peripherals)];
+
 void i2c_reset(void) {
     for (size_t i = 0 ; i < MP_ARRAY_SIZE(twim_peripherals); i++) {
+        if (never_reset[i]) {
+            continue;
+        }
         nrf_twim_disable(twim_peripherals[i].twim.p_twim);
         twim_peripherals[i].in_use = false;
     }
 }
 
+void common_hal_busio_i2c_never_reset(busio_i2c_obj_t *self) {
+    for (size_t i = 0 ; i < MP_ARRAY_SIZE(twim_peripherals); i++) {
+        if (self->twim_peripheral == &twim_peripherals[i]) {
+            never_reset[i] = true;
+
+            never_reset_pin_number(self->scl_pin_number);
+            never_reset_pin_number(self->sda_pin_number);
+            break;
+        }
+    }
+}
+
 static uint8_t twi_error_to_mp(const nrfx_err_t err) {
     switch (err) {
     case NRFX_ERROR_DRV_TWI_ERR_ANACK:
diff --git a/ports/nrf/common-hal/busio/SPI.c b/ports/nrf/common-hal/busio/SPI.c
index 6ab6d9493..5f1aac193 100644
--- a/ports/nrf/common-hal/busio/SPI.c
+++ b/ports/nrf/common-hal/busio/SPI.c
@@ -61,7 +61,7 @@ STATIC spim_peripheral_t spim_peripherals[] = {
 #endif
 };
 
-STATIC bool never_reset[4];
+STATIC bool never_reset[MP_ARRAY_SIZE(spim_peripherals)];
 
 void spi_reset(void) {
     for (size_t i = 0 ; i < MP_ARRAY_SIZE(spim_peripherals); i++) {