From 4b41fdb586f71df283126b012f589b2b746bca12 Mon Sep 17 00:00:00 2001 From: Jeff Epler Date: Thu, 14 Sep 2023 14:20:37 -0500 Subject: [PATCH] Fast(ish) special purpose bitbang spi over i2c with the i2c bus operating at 400kHz this achieves a 4.8kHz SPI clock rate which could be worse. It accepts the same style of init sequence as displayio. tested by scoping the pins on the espressif lcd dev kit with a dummy init sequence: ```python dotclockframebuffer.ioexpander_send_init_sequence( bus=bus, i2c_address=expander_addr, gpio_address=1, gpio_data_len=1, gpio_data=0xff, cs_bit=1, mosi_bit=3, clk_bit=2, init_sequence=init_sequence) ``` --- py/circuitpy_defns.mk | 1 + .../dotclockframebuffer/__init__.c | 93 +++++++++++++++++++ .../dotclockframebuffer/__init__.h | 29 ++++++ shared-module/dotclockframebuffer/__init__.c | 75 +++++++++++++++ 4 files changed, 198 insertions(+) create mode 100644 shared-module/dotclockframebuffer/__init__.c diff --git a/py/circuitpy_defns.mk b/py/circuitpy_defns.mk index 8be49dca0d..c819d46db8 100644 --- a/py/circuitpy_defns.mk +++ b/py/circuitpy_defns.mk @@ -603,6 +603,7 @@ SRC_SHARED_MODULE_ALL = \ displayio/TileGrid.c \ displayio/area.c \ displayio/__init__.c \ + dotclockframebuffer/__init__.c \ floppyio/__init__.c \ fontio/BuiltinFont.c \ fontio/__init__.c \ diff --git a/shared-bindings/dotclockframebuffer/__init__.c b/shared-bindings/dotclockframebuffer/__init__.c index a91964988a..07f9f826dd 100644 --- a/shared-bindings/dotclockframebuffer/__init__.c +++ b/shared-bindings/dotclockframebuffer/__init__.c @@ -34,11 +34,104 @@ #include "shared-bindings/dotclockframebuffer/DotClockFramebuffer.h" //| """Native helpers for driving parallel displays""" +//| +//| Length = typing.Literal[1, 2] +//| +//| def ioexpander_send_init_sequence( +//| bus: busio.I2C, +//| i2c_address: int, +//| reg_addr: int, +//| gpio_data_len: Length, +//| gpio_address: int, +//| gpio_data: int, +//| cs_bit: int, +//| mosi_bit: int, +//| clk_bit: int, +//| init_sequence: ReadableBuffer, +//| ): +//| """Send a displayio-style initialization sequence over an I2C I/O expander +//| +//| This function is highly generic in order to support various I/O expanders. +//| What's assumed is that all the GPIO can be updated by writing to a single I2C register. +//| Normal output polarity is assumed (CS and CLK are active low, data is not inverted). +//| Only 8-bit I2C addresses are supported. +//| 8- and 16-bit I2C addresses and data registers are supported. +//| The Data/Command bit is sent as part of the serial data. +//| +//| Normally this function is used via a convenience library that is specific to the display & I/O expander in use. +//| +//| :param busio.I2C bus: The I2C bus where the I/O expander resides +//| :param busio.i2c_address: int: The I2C bus address of the I/O expander +//| :param int gpio_address: The address portion of the I2C transaction (1 byte) +//| :param int gpio_data_len: The size of the data portion of the I2C transaction, 1 or 2 bytes +//| :param int gpio_data: The output value for all GPIO bits other than cs, mosi, and clk (needed because GPIO expanders may be unable to read back the current output value) +//| :param int cs_bit: The bit number (from 0 to 7, or from 0 to 15) of the chip select bit in the GPIO register +//| :param int mosi_value: The bit number (from 0 to 7, or from 0 to 15) of the data out bit in the GPIO register +//| :param int clk_value: The bit number (from 0 to 7, or from 0 to 15) of the clock out bit in the GPIO register +//| """ +//| +STATIC mp_obj_t ioexpander_send_init_sequence(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) { + enum { ARG_bus, ARG_i2c_address, ARG_gpio_address, ARG_gpio_data_len, ARG_gpio_data, ARG_cs_bit, ARG_mosi_bit, ARG_clk_bit, ARG_init_sequence, NUM_ARGS }; + + static const mp_arg_t allowed_args[] = { + { MP_QSTR_bus, MP_ARG_REQUIRED | MP_ARG_OBJ }, + { MP_QSTR_i2c_address, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_gpio_address, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_gpio_data_len, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_gpio_data, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_cs_bit, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_mosi_bit, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_clk_bit, MP_ARG_REQUIRED | MP_ARG_INT }, + { MP_QSTR_init_sequence, MP_ARG_REQUIRED | MP_ARG_OBJ }, + }; + + mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)]; + MP_STATIC_ASSERT(MP_ARRAY_SIZE(allowed_args) == NUM_ARGS); + mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args); + + mp_obj_t bus_obj = mp_arg_validate_type(args[ARG_bus].u_obj, &busio_i2c_type, MP_QSTR_bus); + mp_int_t i2c_address = args[ARG_i2c_address].u_int; + mp_int_t gpio_address = args[ARG_gpio_address].u_int; + mp_int_t gpio_data_len = args[ARG_gpio_data_len].u_int; + mp_int_t gpio_data = args[ARG_gpio_data].u_int; + mp_int_t cs_bit = args[ARG_cs_bit].u_int; + mp_int_t mosi_bit = args[ARG_mosi_bit].u_int; + mp_int_t clk_bit = args[ARG_clk_bit].u_int; + + mp_buffer_info_t bufinfo; + mp_get_buffer_raise(args[ARG_init_sequence].u_obj, &bufinfo, MP_BUFFER_READ); + + mp_arg_validate_int_range(i2c_address, 0, 127, MP_QSTR_i2c_address); + mp_arg_validate_int_range(gpio_data_len, 1, 2, MP_QSTR_gpio_dat_len); + + int max_bit = gpio_data_len * 8 - 1; + mp_arg_validate_int_range(cs_bit, 0, max_bit, MP_QSTR_cs_bit); + mp_arg_validate_int_range(mosi_bit, 0, max_bit, MP_QSTR_mosi_bit); + mp_arg_validate_int_range(clk_bit, 0, max_bit, MP_QSTR_clk_bit); + mp_arg_validate_int_range(gpio_data, 0, (1 << (max_bit * 8)) - 1, MP_QSTR_gpio_data); + + dotclockframebuffer_ioexpander_spi_bus b = { + .bus = bus_obj, + .i2c_device_address = i2c_address, + .i2c_write_size = 1 + gpio_data_len, + // ASSERT(LITTLE_ENDIAN, "don't have to differentiate 8- vs 16-bits here") + .addr_reg_shadow = { .u32 = gpio_address | (gpio_data << 8) }, + .cs_mask = 0x100 << cs_bit, + .mosi_mask = 0x100 << mosi_bit, + .clk_mask = 0x100 << clk_bit, + }; + + dotclockframebuffer_ioexpander_send_init_sequence(&b, bufinfo.buf, bufinfo.len); + return mp_const_none; +} + +STATIC MP_DEFINE_CONST_FUN_OBJ_KW(ioexpander_send_init_sequence_obj, 0, ioexpander_send_init_sequence); STATIC const mp_rom_map_elem_t dotclockframebuffer_module_globals_table[] = { { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_dotclockframebuffer) }, { MP_ROM_QSTR(MP_QSTR_DotClockFramebuffer), MP_ROM_PTR(&dotclockframebuffer_framebuffer_type) }, + { MP_ROM_QSTR(MP_QSTR_ioexpander_send_init_sequence), MP_ROM_PTR(&ioexpander_send_init_sequence_obj) }, }; STATIC MP_DEFINE_CONST_DICT(dotclockframebuffer_module_globals, dotclockframebuffer_module_globals_table); diff --git a/shared-bindings/dotclockframebuffer/__init__.h b/shared-bindings/dotclockframebuffer/__init__.h index f7b42875a1..e51b5b9a86 100644 --- a/shared-bindings/dotclockframebuffer/__init__.h +++ b/shared-bindings/dotclockframebuffer/__init__.h @@ -25,3 +25,32 @@ */ #pragma once + +#include "py/obj.h" +#include "shared-bindings/busio/I2C.h" + +typedef union { + struct { + uint8_t addr, data; + } a8d8; + struct { + uint16_t addr, data; // in little endian + } a16d16; + struct { + uint8_t addr; + uint16_t data; // in little endian + } __attribute__((packed)) a8d16; + uint32_t u32; +} dotclockframebuffer_ioexpander_addr_reg_t; + +typedef struct { + busio_i2c_obj_t *bus; + uint8_t i2c_device_address; + uint8_t i2c_write_size; + dotclockframebuffer_ioexpander_addr_reg_t addr_reg_shadow; + uint32_t cs_mask; + uint32_t mosi_mask; + uint32_t clk_mask; +} dotclockframebuffer_ioexpander_spi_bus; + +void dotclockframebuffer_ioexpander_send_init_sequence(dotclockframebuffer_ioexpander_spi_bus *bus, uint8_t *init_sequence, uint16_t init_sequence_len); diff --git a/shared-module/dotclockframebuffer/__init__.c b/shared-module/dotclockframebuffer/__init__.c new file mode 100644 index 0000000000..55329a87f6 --- /dev/null +++ b/shared-module/dotclockframebuffer/__init__.c @@ -0,0 +1,75 @@ +#include "shared-bindings/dotclockframebuffer/__init__.h" + +#include +#include +#include + +#define DELAY (0x80) + +static void pin_change(dotclockframebuffer_ioexpander_spi_bus *bus, uint32_t set_bits, uint32_t clear_bits) { + uint32_t data = (bus->addr_reg_shadow.u32 & ~clear_bits) | set_bits; + // no way to signal failure to caller! + (void)common_hal_busio_i2c_write(bus->bus, bus->i2c_device_address, (uint8_t *)&data, bus->i2c_write_size); + bus->addr_reg_shadow.u32 = data; +} + +static void ioexpander_bus_send(dotclockframebuffer_ioexpander_spi_bus *bus, + bool is_command, + const uint8_t *data, uint32_t data_length) { + + int dc_mask = is_command ? 0 : 0x100; + for (uint32_t i = 0; i < data_length; i++) { + int bits = data[i] | dc_mask; + + for (uint32_t j = 0; j < 9; j++) { + // CPOL=CPHA=0: output fresh data on falling edge of clk or cs + if (bits & 0x100) { + pin_change(bus, /* set */ bus->mosi_mask, /* clear */ bus->clk_mask | bus->cs_mask); + } else { + pin_change(bus, /* set */ 0, /* clear */ bus->mosi_mask | bus->clk_mask | bus->cs_mask); + } + // Display latches bit on rising edge of CLK + pin_change(bus, /* set */ bus->clk_mask, /* clear */ 0); + + // next bit + bits <<= 1; + } + } +} + +// Send a circuitpython-style display initialization sequence over an i2c-attached bus expander +// This always assumes +// * 9-bit SPI (no DC pin) +// * CPOL=CPHA=0 +// * CS deasserted after each init sequence step, but not otherwise just like +// displayio fourwire bus without data_as_commands +void dotclockframebuffer_ioexpander_send_init_sequence(dotclockframebuffer_ioexpander_spi_bus *bus, uint8_t *init_sequence, uint16_t init_sequence_len) { + while (!common_hal_busio_i2c_try_lock(bus->bus)) { + RUN_BACKGROUND_TASKS; + } + for (uint32_t i = 0; i < init_sequence_len; /* NO INCREMENT */) { + uint8_t *cmd = init_sequence + i; + uint8_t data_size = *(cmd + 1); + bool delay = (data_size & DELAY) != 0; + data_size &= ~DELAY; + uint8_t *data = cmd + 2; + + ioexpander_bus_send(bus, true, cmd, 1); + ioexpander_bus_send(bus, false, data, data_size); + + // deassert CS + pin_change(bus, /* set */ bus->cs_mask, /* clear */ 0); + + uint16_t delay_length_ms = 10; + if (delay) { + data_size++; + delay_length_ms = *(cmd + 1 + data_size); + if (delay_length_ms == 255) { + delay_length_ms = 500; + } + } + mp_hal_delay_ms(delay_length_ms); + i += 2 + data_size; + } + common_hal_busio_i2c_unlock(bus->bus); +}