From 102ee716a7430acaca6eb223f3a06df1d34a257b Mon Sep 17 00:00:00 2001 From: Radomir Dopieralski Date: Thu, 3 Mar 2022 22:42:50 +0100 Subject: [PATCH] Add support for 9-bit mode to displayio.FourWire If the ``command`` pin is None, that information will instead be sent as a ninth bit in the SPI transactions. Fix #6109 --- shared-bindings/displayio/FourWire.c | 13 ++++-- shared-module/displayio/FourWire.c | 61 ++++++++++++++++++++++++---- 2 files changed, 61 insertions(+), 13 deletions(-) diff --git a/shared-bindings/displayio/FourWire.c b/shared-bindings/displayio/FourWire.c index ead9e418dc..90aa5c6c17 100644 --- a/shared-bindings/displayio/FourWire.c +++ b/shared-bindings/displayio/FourWire.c @@ -43,7 +43,7 @@ //| """Manage updating a display over SPI four wire protocol in the background while Python code runs. //| It doesn't handle display initialization.""" //| -//| def __init__(self, spi_bus: busio.SPI, *, command: microcontroller.Pin, chip_select: microcontroller.Pin, reset: Optional[microcontroller.Pin] = None, baudrate: int = 24000000, polarity: int = 0, phase: int = 0) -> None: +//| def __init__(self, spi_bus: busio.SPI, *, command: Optional[microcontroller.Pin], chip_select: microcontroller.Pin, reset: Optional[microcontroller.Pin] = None, baudrate: int = 24000000, polarity: int = 0, phase: int = 0) -> None: //| """Create a FourWire object associated with the given pins. //| //| The SPI bus and pins are then in use by the display until `displayio.release_displays()` is @@ -51,8 +51,13 @@ //| is done.) So, the first time you initialize a display bus in code.py you should call //| :py:func:`displayio.release_displays` first, otherwise it will error after the first code.py run. //| +//| If the ``command`` pin is not specified, a 9-bit SPI mode will be simulated by adding a +//| data/command bit to every bit being transmitted, and splitting the resulting data back +//| into 8-bit bytes for transmission. The extra bits that this creates at the end are ignored +//| by the receiving device. +//| //| :param busio.SPI spi_bus: The SPI bus that make up the clock and data lines -//| :param microcontroller.Pin command: Data or command pin +//| :param microcontroller.Pin command: Data or command pin. When None, 9-bit SPI is simulated. //| :param microcontroller.Pin chip_select: Chip select pin //| :param microcontroller.Pin reset: Reset pin. When None only software reset can be used //| :param int baudrate: Maximum baudrate in Hz for the display on the bus @@ -65,7 +70,7 @@ STATIC mp_obj_t displayio_fourwire_make_new(const mp_obj_type_t *type, size_t n_ enum { ARG_spi_bus, ARG_command, ARG_chip_select, ARG_reset, ARG_baudrate, ARG_polarity, ARG_phase }; static const mp_arg_t allowed_args[] = { { MP_QSTR_spi_bus, MP_ARG_REQUIRED | MP_ARG_OBJ }, - { MP_QSTR_command, MP_ARG_OBJ | MP_ARG_KW_ONLY | MP_ARG_REQUIRED }, + { MP_QSTR_command, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none} }, { MP_QSTR_chip_select, MP_ARG_OBJ | MP_ARG_KW_ONLY | MP_ARG_REQUIRED }, { MP_QSTR_reset, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none} }, { MP_QSTR_baudrate, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 24000000} }, @@ -75,7 +80,7 @@ STATIC mp_obj_t displayio_fourwire_make_new(const mp_obj_type_t *type, size_t n_ mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)]; mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args); - const mcu_pin_obj_t *command = validate_obj_is_free_pin(args[ARG_command].u_obj); + const mcu_pin_obj_t *command = validate_obj_is_free_pin_or_none(args[ARG_command].u_obj); const mcu_pin_obj_t *chip_select = validate_obj_is_free_pin(args[ARG_chip_select].u_obj); const mcu_pin_obj_t *reset = validate_obj_is_free_pin_or_none(args[ARG_reset].u_obj); diff --git a/shared-module/displayio/FourWire.c b/shared-module/displayio/FourWire.c index 59e2021bd8..41d43400f9 100644 --- a/shared-module/displayio/FourWire.c +++ b/shared-module/displayio/FourWire.c @@ -51,11 +51,16 @@ void common_hal_displayio_fourwire_construct(displayio_fourwire_obj_t *self, self->polarity = polarity; self->phase = phase; - common_hal_digitalio_digitalinout_construct(&self->command, command); - common_hal_digitalio_digitalinout_switch_to_output(&self->command, true, DRIVE_MODE_PUSH_PULL); 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->command.base.type = &mp_type_NoneType; + if (command != NULL) { + self->command.base.type = &digitalio_digitalinout_type; + common_hal_digitalio_digitalinout_construct(&self->command, command); + common_hal_digitalio_digitalinout_switch_to_output(&self->command, true, DRIVE_MODE_PUSH_PULL); + common_hal_never_reset_pin(command); + } self->reset.base.type = &mp_type_NoneType; if (reset != NULL) { self->reset.base.type = &digitalio_digitalinout_type; @@ -65,7 +70,6 @@ void common_hal_displayio_fourwire_construct(displayio_fourwire_obj_t *self, common_hal_displayio_fourwire_reset(self); } - common_hal_never_reset_pin(command); common_hal_never_reset_pin(chip_select); } @@ -114,18 +118,57 @@ bool common_hal_displayio_fourwire_begin_transaction(mp_obj_t obj) { void common_hal_displayio_fourwire_send(mp_obj_t obj, display_byte_type_t data_type, display_chip_select_behavior_t chip_select, const uint8_t *data, uint32_t data_length) { displayio_fourwire_obj_t *self = MP_OBJ_TO_PTR(obj); - common_hal_digitalio_digitalinout_set_value(&self->command, data_type == DISPLAY_DATA); - if (chip_select == CHIP_SELECT_TOGGLE_EVERY_BYTE) { - // Toggle chip select after each command byte in case the display driver - // IC latches commands based on it. + if (self->command.base.type == &mp_type_NoneType) { + // When the data/command pin is not specified, we simulate a 9-bit SPI mode, by + // adding a data/command bit to every byte, and then splitting the resulting data back + // into 8-bit chunks for transmission. If the length of the data being transmitted + // is not a multiple of 8, there will be additional bits at the end of the + // transmission. We toggle the CS pin to make the receiver discard them. + uint8_t buffer = 0; + uint8_t bits = 0; + uint8_t dc = (data_type == DISPLAY_DATA); + for (size_t i = 0; i < data_length; i++) { - common_hal_busio_spi_write(self->bus, &data[i], 1); + bits = (bits + 1) % 8; + + if (bits == 0) { + // send the previous byte and the dc bit + // we will send the current byte later + buffer = (buffer << 1) | dc; + common_hal_busio_spi_write(self->bus, &buffer, 1); + // send the current byte, because previous byte already filled all bits + common_hal_busio_spi_write(self->bus, &data[i], 1); + } else { + // send remaining bits from previous byte, dc and beginning of current byte + buffer = (buffer << (9 - bits)) | (dc << (8 - bits)) | (data[i] >> bits); + common_hal_busio_spi_write(self->bus, &buffer, 1); + } + // save the current byte + buffer = data[i]; + } + // send any remaining bits + if (bits > 0) { + buffer = buffer << (8 - bits); + common_hal_busio_spi_write(self->bus, &buffer, 1); + // toggle CS to discard superfluous bits common_hal_digitalio_digitalinout_set_value(&self->chip_select, true); common_hal_mcu_delay_us(1); common_hal_digitalio_digitalinout_set_value(&self->chip_select, false); } } else { - common_hal_busio_spi_write(self->bus, data, data_length); + common_hal_digitalio_digitalinout_set_value(&self->command, data_type == DISPLAY_DATA); + if (chip_select == CHIP_SELECT_TOGGLE_EVERY_BYTE) { + // Toggle chip select after each command byte in case the display driver + // IC latches commands based on it. + for (size_t i = 0; i < data_length; i++) { + common_hal_busio_spi_write(self->bus, &data[i], 1); + common_hal_digitalio_digitalinout_set_value(&self->chip_select, true); + common_hal_mcu_delay_us(1); + common_hal_digitalio_digitalinout_set_value(&self->chip_select, false); + } + } else { + common_hal_busio_spi_write(self->bus, data, data_length); + } } }