nrf_drv_twi_rx() returns SUCCESS but sends NAK to the slave

[asantos]

Hello,

I am interfacing a NRF52832 with a PCF8574 I2C slave using SDK 15.0.0.

As per the datasheet, the device will send the data to the slave after it receives the write byte from the master, then the master should send an ACK:

I am using the following code in order to read from the slave:

ret_code_t err_code = nrf_drv_twi_rx(&m_i2c_instance, slave_i2c_addr, p_buf, length);

The function returns NRF_SUCCESS and the slave data is read properly into the buffer, however the master doesn't send ACK. Am I doing something wrong?

Please see the Logic analyzer capture below:

Thank you

[Turbo J]

asantos said:

Am I doing something wrong?

You did not read the I²C bus spec. The last byte is always NAKed on a I²C master read transaction IIRC.