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// Software I2C emulation
//
// Copyright (C) 2023-2025 Kevin O'Connor <kevin@koconnor.net>
// Copyright (C) 2023 Alan.Ma <tech@biqu3d.com>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <string.h> // memcpy
#include "autoconf.h" // CONFIG_CLOCK_FREQ
#include "board/gpio.h" // gpio_out_setup
#include "board/internal.h" // gpio_peripheral
#include "board/misc.h" // timer_read_time
#include "basecmd.h" // oid_alloc
#include "command.h" // DECL_COMMAND
#include "i2ccmds.h" // i2cdev_set_software_bus
struct i2c_software {
struct gpio_out scl_out, sda_out;
struct gpio_in scl_in, sda_in;
uint8_t addr;
uint32_t ticks;
};
void
command_i2c_set_sw_bus(uint32_t *args)
{
struct i2cdev_s *i2c = i2cdev_oid_lookup(args[0]);
struct i2c_software *is = alloc_chunk(sizeof(*is));
is->ticks = args[3];
is->addr = (args[4] & 0x7f) << 1; // address format shifted
is->scl_in = gpio_in_setup(args[1], 1);
is->scl_out = gpio_out_setup(args[1], 1);
is->sda_in = gpio_in_setup(args[2], 1);
is->sda_out = gpio_out_setup(args[2], 1);
i2cdev_set_software_bus(i2c, is);
}
DECL_COMMAND(command_i2c_set_sw_bus,
"i2c_set_sw_bus oid=%c scl_pin=%u sda_pin=%u"
" pulse_ticks=%u address=%u");
// The AVR micro-controllers require specialized timing
#if CONFIG_MACH_AVR
#define i2c_delay(ticks) (void)(ticks)
#else
static void
i2c_delay(uint32_t ticks)
{
uint32_t end = timer_read_time() + ticks;
while (timer_is_before(timer_read_time(), end))
;
}
#endif
static void
i2c_software_send_ack(struct i2c_software *is, const uint8_t ack)
{
if (!ack) {
gpio_out_reset(is->sda_out, 0);
}
i2c_delay(is->ticks);
gpio_in_reset(is->scl_in, 1);
i2c_delay(is->ticks);
gpio_out_reset(is->scl_out, 0);
}
static uint8_t
i2c_software_read_ack(struct i2c_software *is, uint_fast8_t state)
{
uint8_t nack = 0;
if (state == 0)
gpio_in_reset(is->sda_in, 1);
i2c_delay(is->ticks);
gpio_in_reset(is->scl_in, 1);
nack = gpio_in_read(is->sda_in);
i2c_delay(is->ticks);
gpio_out_reset(is->scl_out, 0);
return nack;
}
static int
i2c_software_send_byte(struct i2c_software *is, uint8_t b)
{
uint_fast8_t state = 2;
for (uint_fast8_t i = 0; i < 8; i++) {
if (b & 0x80) {
if (state != 1)
gpio_in_reset(is->sda_in, 1);
state = 1;
} else {
if (state > 0)
gpio_out_reset(is->sda_out, 0);
state = 0;
}
b <<= 1;
i2c_delay(is->ticks);
gpio_in_reset(is->scl_in, 1);
i2c_delay(is->ticks);
gpio_out_reset(is->scl_out, 0);
}
if (i2c_software_read_ack(is, state)) {
return I2C_BUS_NACK;
}
return I2C_BUS_SUCCESS;
}
static uint8_t
i2c_software_read_byte(struct i2c_software *is, uint8_t remaining)
{
uint8_t b = 0;
gpio_in_reset(is->sda_in, 1);
for (uint_fast8_t i = 0; i < 8; i++) {
i2c_delay(is->ticks);
gpio_in_reset(is->scl_in, 1);
i2c_delay(is->ticks);
b <<= 1;
b |= gpio_in_read(is->sda_in);
gpio_out_reset(is->scl_out, 0);
}
i2c_software_send_ack(is, remaining == 0);
return b;
}
static int
i2c_software_start(struct i2c_software *is, uint8_t addr)
{
int ret;
i2c_delay(is->ticks);
gpio_in_reset(is->sda_in, 1);
gpio_in_reset(is->scl_in, 1);
i2c_delay(is->ticks);
gpio_out_reset(is->sda_out, 0);
i2c_delay(is->ticks);
gpio_out_reset(is->scl_out, 0);
ret = i2c_software_send_byte(is, addr);
if (ret == I2C_BUS_NACK)
return I2C_BUS_START_NACK;
return ret;
}
static void
i2c_software_stop(struct i2c_software *is)
{
gpio_out_reset(is->sda_out, 0);
i2c_delay(is->ticks);
gpio_in_reset(is->scl_in, 1);
i2c_delay(is->ticks);
gpio_in_reset(is->sda_in, 1);
}
int
i2c_software_write(struct i2c_software *is, uint8_t write_len, uint8_t *write)
{
int ret = i2c_software_start(is, is->addr);
if (ret != I2C_BUS_SUCCESS)
goto out;
while (write_len--) {
ret = i2c_software_send_byte(is, *write++);
if (ret != I2C_BUS_SUCCESS)
break;
}
out:
i2c_software_stop(is);
return ret;
}
int
i2c_software_read(struct i2c_software *is, uint8_t reg_len, uint8_t *reg
, uint8_t read_len, uint8_t *read)
{
int ret;
if (reg_len) {
// write the register
ret = i2c_software_start(is, is->addr);
if (ret != I2C_BUS_SUCCESS)
goto out;
while(reg_len--) {
ret = i2c_software_send_byte(is, *reg++);
if (ret != I2C_BUS_SUCCESS)
goto out;
}
}
// start/re-start and read data
ret = i2c_software_start(is, is->addr | 0x01);
if (ret != I2C_BUS_SUCCESS) {
ret = I2C_BUS_START_READ_NACK;
goto out;
}
while(read_len--) {
*read = i2c_software_read_byte(is, read_len);
read++;
}
out:
i2c_software_stop(is);
return ret;
}
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