From 929d98538e325e96f0a13d8b3cc5d4a03dd75573 Mon Sep 17 00:00:00 2001 From: chuck todd Date: Sun, 30 Sep 2018 14:47:05 -0600 Subject: [PATCH] 1. Slow down I2C to 100khz During Reset I am stealing this delay coding from @jeremyherbert #2493 pr. 2. Change Bus Reset to handle interrupted READ sequences. The current code does not handle interrupted READ cycles. 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 byte READ 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. The master(ESP32) cannot generate a STOP unless SDA is HIGH. So, this reset code synchronizes the bit stream with, Either, the ACK bit, Or a 1 bit. 3. fix typo correct `sda_id` to `sda_io` in `i2c_master_clear_bus()` @ryan-ma found it. This typo was generated when I manually edited this patch on GitHub, I should have done a Copy/Paste operation! --- components/driver/i2c.c | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/components/driver/i2c.c b/components/driver/i2c.c index 2d1a832c5..44133d655 100644 --- a/components/driver/i2c.c +++ b/components/driver/i2c.c @@ -537,27 +537,29 @@ static esp_err_t i2c_master_clear_bus(i2c_port_t i2c_num) 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. gpio_set_direction(scl_io, GPIO_MODE_OUTPUT_OD); gpio_set_direction(sda_io, GPIO_MODE_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. int scl_half_period = 5; // use standard 100kHz data rate + gpio_set_level(scl_io, 0); gpio_set_level(sda_io, 1); ets_delay_us(scl_half_period); - gpio_set_level(scl_io, 1); - ets_delay_us(scl_half_period); - for (int i = 0; i < 9; i++) { - gpio_set_level(scl_io, 0); - ets_delay_us(scl_half_period); + int i=0; + while( !gpio_get_level(sda_io) && (i<9)){ // cycle SCL until SDA is HIGH gpio_set_level(scl_io, 1); ets_delay_us(scl_half_period); + gpio_set_level(scl_io, 0); + ets_delay_us(scl_half_period); + i++; } - gpio_set_level(sda_io, 0); // setup stop condition (this is an implicit start condition) + 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); // generate stop condition - 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; }