TWI stops working - SDA bus always LOW

[Rafa]

Hi!

I'm developing a project with nrf52832 and I'm getting some problems. The micro is only communicating with an accelerometer (MMA8453) and after some time the communication stops. Using a digital analyzer is possible observe that the SDA bus get stuck in LOW. I already tried to change the PULL UP resistors to smaller values (2.74k) and it keeps happening. I tried communicate with other slave and the same happens.

To fix that, I changed the configurations of nrf_drv_twi.c to work in push pull mode instead of pull up mode. I don't know if it is the correct way to do it.

I'm using the pins P02 (SDA) and P03(SCL) and changed the configuration to the following:

nrf_drv_twi_config_t twi_config;
twi_config.scl = CGPIO::I2C_SCL;
twi_config.sda = CGPIO::I2C_SDA;
twi_config.frequency = NRF_TWI_FREQ_250K;
twi_config.interrupt_priority = APP_IRQ_PRIORITY_HIGH;
    
nrf_drv_twi_init(&i2c_instance, &twi_config, NULL, NULL);
nrf_drv_twi_enable(&i2c_instance);

---

#define SCL_PIN_INIT_CONF     ( (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos) \
                              | (GPIO_PIN_CNF_DRIVE_S0S1     << GPIO_PIN_CNF_DRIVE_Pos) \
                              | (GPIO_PIN_CNF_PULL_Pullup    << GPIO_PIN_CNF_PULL_Pos)  \
                              | (GPIO_PIN_CNF_INPUT_Connect  << GPIO_PIN_CNF_INPUT_Pos) \
                              | (GPIO_PIN_CNF_DIR_Input      << GPIO_PIN_CNF_DIR_Pos))
#define SDA_PIN_INIT_CONF        SCL_PIN_INIT_CONF

[RK]

The drive configuration of the pins is irrelevant once the TWI module takes control of them, it only matters when the chip is in a sleep mode where the pins need to be driven to a certain level. So you can change it as much as you like and it won't make a difference.

If SDA is being held low it's because one of the two devices is holding it low. Unfortunately it's rather hard to tell which that is unless you can measure the current into each device. You need to get some kind of analyzer trace of the signals and work out which device last had control of the bus, and why it's not releasing it.