nrf_twi examples

[Yano]

Hi, I'm moving form using the driver twi_master (hardware) to nrf_twi/nrf_drv_twi. I can't find any sample code? Does anyone have a nrf_twi example code? Thanks

[Krzysztof Chruscinski]

Simplest to start would be to use non-blocking mode (initializing driver with NULL event handler). Code snippet below would first transfer 2 bytes and then continue transaction (xfer_pending=true) expecting to receive 4 bytes. Both calls (rx&tx) are blocking and return only after requested data is transferred. To achieve better performance you can try non-blocking mode where tx&rx functions are returning once transfer is setup. Application is notified about transfer completion by event handler.

uint32_t err_code;
uint8_t tx_data[] = {'a', 'b'};
uint8_t rx_data[4];
const nrf_drv_twi_t twi = NRF_DRV_TWI_INSTANCE(0);

err_code = nrf_drv_twi_init(&twi, NULL, NULL);
APP_ERROR_CHECK(err_code);

nrf_drv_twi_enable(&twi);

err_code = nrf_drv_twi_tx(&twi, SLAVE_ADDRESS, tx_data, sizeof(tx_data), true);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_twi_rx(&twi, SLAVE_ADDRESS, rx_data, sizeof(rx_data), false);
APP_ERROR_CHECK(err_code);

Non-blocking mode is used if event_handler function is provided during initialization.

void event_handler(nrf_drv_twi_evt_t * p_event)
{
    if (p_event->type == NRF_DRV_TWI_RX_DONE){...}
}

Then function nrf_drv_twi_tx and nrf_drv_twi_rx returns immediately and event handler is called in the context of TWI interrupt. Event contains also pointer to the buffer and amount of data transmitted or received.

[merlinmag]

Thanks for answer Panie Krzysztofie :) But what about non-blocking mode? How to use received data event handler?