No NAK reported with TWI driver?

RE: No NAK reported with TWI driver?

David Russell — Mon, 20 Jun 2016 22:37:06 GMT

It turns out the FTDI datasheet from which I was comparing the waveform had an error. The ACK bit I was looking at was supposed to be a NAK coming from the master indicating the end of the transfer. The datasheet showed the slave device outputting an ACK after it wrote its own data byte which is incorrect.

RE: No NAK reported with TWI driver?

David Russell — Mon, 20 Jun 2016 18:05:53 GMT

I was using the driver in blocking mode. That said, I tried adding an event handler; but I received the same result -- the event handler callback said that the byte was read when the slave device was actually nacking the transaction.

RE: No NAK reported with TWI driver?

Quinn — Mon, 20 Jun 2016 06:15:30 GMT

Hi,

I think you should wait a event is done before reading and writing next command. Setup event as below

....
err_code = nrf_drv_twi_init(&m_twi_handle, &nrf_drv_twi_config, twi_handler, NULL);
APP_ERROR_CHECK(err_code);
....

// handler function

void twi_handler(nrf_drv_twi_evt_t const * p_event, void * p_context)
{
	switch(p_event->type)
    {
        case NRF_DRV_TWI_EVT_DONE:
            if (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_TX)
            {
                m_tx_done = true;
            }
            else if (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_RX)
            {
                m_rx_done = true;
            }
            else{
            	NRF_LOG_PRINTF(NRF_LOG_COLOR_RED "Don't have event type\n");
            }
            break;
        case NRF_DRV_TWI_EVT_ADDRESS_NACK:
        	NRF_LOG_PRINTF(NRF_LOG_COLOR_RED "TWI NRF_DRV_TWI_EVT_ADDRESS_NACK\n");
        	break;
        case NRF_DRV_TWI_EVT_DATA_NACK:
        	NRF_LOG_PRINTF(NRF_LOG_COLOR_RED "TWI NRF_DRV_TWI_EVT_DATA_NACK\n");
            break;
        default:
            break;
    }

}

Good luck!