TWI Slave Sample

[Junichi]

I'm thinking of incorporating a TWI slave with nRF52832.

I'm using SDK 17.0.2.

I want to set up a register and read/write multiple bytes with TWI, but I don't know how to write the twis_event_handler process.

Are there any good samples?

[Priyanka]

Hi,

Please take a look at the TWIS driver.

There is also a sample implementation mentioned here: https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/hardware_driver_twis_slave.html#twi_slave_asynchronous_mode:~:text=void%20twis_event_handler(nrf_drv_twis_evt_t%20const%20*%20const%20p_event) 

Please also take a look at the TWIS implementation guide: https://devzone.nordicsemi.com/guides/nrf-connect-sdk-guides/b/peripherals/posts/twi-ic2-implementation-with-nrfx-twis-driver#mcetoc_1fc9idhsd3

Regards,

Priyanka 

[Junichi]

Thank you for the information.

Currently, I can read from the master, but write operations don't work properly because an NRFX_TWIS_EVT_GENERAL_ERROR occurs.

When I look with a protocol analyzer, I can see that ACKs are returned up to the slave address and register address, but no ACK is returned for data, and in the slave event, I can read the register address but not the data.

What do you think is the cause?

I've attached the source code for the current event handler.

void twis_event_handler(nrf_drv_twis_evt_t const * p_event)
{
     static bool address_received = false; 

    switch (p_event->type)
    {
        case NRFX_TWIS_EVT_READ_REQ:
            nrf_drv_twis_tx_prepare(&m_twis, &m_twi_register[m_register_address], TWI_BUFFER_SIZE - m_register_address);
            NRF_LOG_INFO("Read request: register address = 0x%02X", m_register_address);
            break;

        case NRFX_TWIS_EVT_WRITE_REQ:
            if (!address_received) {
                NRF_LOG_INFO("Preparing to receive register address...");
                nrf_drv_twis_rx_prepare(&m_twis, &m_register_address, 1);
            } else {
                NRF_LOG_INFO("Register address received: 0x%02X", m_register_address);
                if (m_register_address < TWI_BUFFER_SIZE) {
                    NRF_LOG_INFO("Preparing to write data to register 0x%02X", m_register_address);
                    nrf_drv_twis_rx_prepare(&m_twis, &m_twi_register[m_register_address], TWI_BUFFER_SIZE - m_register_address);
                } else {
                    NRF_LOG_ERROR("Invalid register address: 0x%02X", m_register_address);
                }
            }
            break;

        case NRFX_TWIS_EVT_WRITE_DONE:
            if (!address_received) {
                address_received = true;
                NRF_LOG_INFO("Register address 0x%02X received", m_register_address);
            } else {
                address_received = false;
                NRF_LOG_INFO("Data written to register 0x%02X: 0x%02X", m_register_address, m_twi_register[m_register_address]);
            }
            break;

        case NRFX_TWIS_EVT_READ_DONE:
            NRF_LOG_INFO("Read completed");
            break;

        case NRFX_TWIS_EVT_READ_ERROR:
            NRF_LOG_ERROR("TWIS EVT READ ERROR");
            break;

        case NRFX_TWIS_EVT_WRITE_ERROR:
            NRF_LOG_ERROR("TWIS EVT WRITE ERROR");
            break;
        
        case NRFX_TWIS_EVT_GENERAL_ERROR:
            NRF_LOG_ERROR("TWIS EVT GENERAL ERROR");
            break;

        default:
            break;
    }
}

[Priyanka]

Hi,

Could you try to prepare the data buffer earlier, in the NRFX_TWIS_EVT_WRITE_REQ phase, irrespective of whether the register address has been received?

You could also make sure that the nrf_drv_twis_rx_prepare() is called quickly enough for the data phase.

Because right now, if there’s a timing issue or race condition, the slave may not have the data buffer ready in time, causing the master to not receive an ACK for the data phase.

Regards,

Priyanka