diff --git a/components/driver/i2c.c b/components/driver/i2c.c index 1fec115896..279cc81d6c 100644 --- a/components/driver/i2c.c +++ b/components/driver/i2c.c @@ -80,6 +80,8 @@ static DRAM_ATTR i2c_dev_t* const I2C[I2C_NUM_MAX] = { &I2C0, &I2C1 }; #define I2C_MASTER_TOUT_CNUM_DEFAULT (8) /* I2C master timeout cycle number of I2C clock, after which the timeout interrupt will be triggered */ #define I2C_ACKERR_CNT_MAX (10) #define I2C_FILTER_CYC_NUM_DEF (7) /* The number of apb cycles filtered by default*/ +#define I2C_CLR_BUS_SCL_NUM (9) +#define I2C_CLR_BUS_HALF_PERIOD_US (5) typedef struct { uint8_t byte_num; /*!< cmd byte number */ @@ -525,7 +527,9 @@ esp_err_t i2c_get_data_mode(i2c_port_t i2c_num, i2c_trans_mode_t *tx_trans_mode, static esp_err_t i2c_master_clear_bus(i2c_port_t i2c_num) { I2C_CHECK(i2c_num < I2C_NUM_MAX, I2C_NUM_ERROR_STR, ESP_ERR_INVALID_ARG); + const int scl_half_period = I2C_CLR_BUS_HALF_PERIOD_US; // use standard 100kHz data rate int sda_in_sig = 0, scl_in_sig = 0; + int i = 0; if (i2c_num == I2C_NUM_0) { sda_in_sig = I2CEXT0_SDA_IN_IDX; scl_in_sig = I2CEXT0_SCL_IN_IDX; @@ -536,19 +540,27 @@ static esp_err_t i2c_master_clear_bus(i2c_port_t i2c_num) int scl_io = GPIO.func_in_sel_cfg[scl_in_sig].func_sel; int sda_io = GPIO.func_in_sel_cfg[sda_in_sig].func_sel; I2C_CHECK((GPIO_IS_VALID_OUTPUT_GPIO(scl_io)), I2C_SCL_IO_ERR_STR, ESP_ERR_INVALID_ARG); - I2C_CHECK((GPIO_IS_VALID_GPIO(sda_io)), I2C_SDA_IO_ERR_STR, ESP_ERR_INVALID_ARG); - // We do not check whether the SDA line is low - // because after some serious interference, the bus may keep high all the time and the i2c bus is out of service. + I2C_CHECK((GPIO_IS_VALID_OUTPUT_GPIO(sda_io)), I2C_SDA_IO_ERR_STR, ESP_ERR_INVALID_ARG); gpio_set_direction(scl_io, GPIO_MODE_OUTPUT_OD); - gpio_set_direction(sda_io, GPIO_MODE_OUTPUT_OD); - gpio_set_level(scl_io, 1); + gpio_set_direction(sda_io, GPIO_MODE_INPUT_OUTPUT_OD); + // If a SLAVE device was in a read operation when the bus was interrupted, the SLAVE device is controlling SDA. + // The only bit during the 9 clock cycles of a READ byte the MASTER(ESP32) is guaranteed control over is during the ACK bit + // period. If the slave is sending a stream of ZERO bytes, it will only release SDA during the ACK bit period. + // So, this reset code needs to synchronize the bit stream with, Either, the ACK bit, Or a 1 bit to correctly generate + // a STOP condition. + gpio_set_level(scl_io, 0); gpio_set_level(sda_io, 1); - gpio_set_level(sda_io, 0); - for (int i = 0; i < 9; i++) { - gpio_set_level(scl_io, 0); + ets_delay_us(scl_half_period); + while(!gpio_get_level(sda_io) && (i++ < I2C_CLR_BUS_SCL_NUM)) { gpio_set_level(scl_io, 1); + ets_delay_us(scl_half_period); + gpio_set_level(scl_io, 0); + ets_delay_us(scl_half_period); } - gpio_set_level(sda_io, 1); + gpio_set_level(sda_io,0); // setup for STOP + gpio_set_level(scl_io,1); + ets_delay_us(scl_half_period); + gpio_set_level(sda_io, 1); // STOP, SDA low -> high while SCL is HIGH i2c_set_pin(i2c_num, sda_io, scl_io, 1, 1, I2C_MODE_MASTER); return ESP_OK; }