nrf52 as TWIS (I2C slave)

Question

Hi.

I'm trying to use nRF52 as TWI slave.

So far done:

Enabled TWIS0 from nrf_drv_cfg.h

  /* TWIS */ 

  #define TWIS0_ENABLED 1

  #if (TWIS0_ENABLED == 1)
  #define TWIS0_CONFIG_ADDR0        0x74
  #define TWIS0_CONFIG_ADDR1        0 /* 0: Disabled */
  #define TWIS0_CONFIG_SCL          0
  #define TWIS0_CONFIG_SDA          1
  #define TWIS0_CONFIG_IRQ_PRIORITY APP_IRQ_PRIORITY_HIGH 
  #define TWIS0_INSTANCE_INDEX      0
  #endif

I get the instance

  static const nrf_drv_twis_t m_twis = NRF_DRV_TWIS_INSTANCE(TWIS0_INSTANCE_INDEX);

Do the initalization before the master does the first call:

  const nrf_drv_twis_config_t config =
  {
   .addr               = {TWIS0_CONFIG_ADDR0, 0},
   .scl                = TWIS0_CONFIG_SCL,
   .sda                = TWIS0_CONFIG_SDA,
   .interrupt_priority = TWIS0_CONFIG_IRQ_PRIORITY
  };

  if(NRF_SUCCESS != nrf_drv_twis_init(&m_twis, &config, twis_event_handler)) {
      NRF_LOG_PRINTF("twis init failed!\n\r");
    } else {
   NRF_LOG_PRINTF("twis init OK!\n\r");
 }

nrf_drv_twis_enable(&m_twis);

I've also got the event handler ready to go.

  void twis_event_handler(nrf_drv_twis_evt_t const * const p_event){

   NRF_LOG_PRINTF("twis_evt: %d\n\r",p_event->type);
   switch(p_event->type) {
   case TWIS_EVT_READ_REQ:
       if(p_event->data.buf_req) {
           (void)nrf_drv_twis_tx_prepare(&m_twis, m_tx_buf, strlen(m_tx_buf));    
       }
       break;
   case TWIS_EVT_READ_DONE:
       memset(m_tx_buf, 0x00, sizeof(m_tx_buf));
       break;
   case TWIS_EVT_WRITE_REQ:
       if(p_event->data.buf_req) {
           (void)nrf_drv_twis_rx_prepare(&m_twis, m_rx_buf, sizeof(m_rx_buf));
       }
       break;
   case TWIS_EVT_WRITE_DONE:
      parse_resp(p_event->data.rx_amount);
      break;

   case TWIS_EVT_READ_ERROR:
   case TWIS_EVT_WRITE_ERROR:
   case TWIS_EVT_GENERAL_ERROR:
    //        m_error_flag = true;
     break;
   default:
      break;
   }
 }

However when then master does the first call with the device address, there's nack on the line. image description

The device address seems OK on the bus 0xE8 (0x74 << 1)and the read bit of the address is ok. We are using 400k clock, however the 100k doesn't seem to do any good either.

Daniel Wang · Accepted Answer

Is this a nrf52-dk? On the DK pin 0 and 1 is connected to the LF crystal, so maybe change the TWIS0_CONFIG_SCL / TWIS0_CONFIG_SDA to some other pins?

nrf52 as TWIS (I2C slave)

Top Replies