Why there is no TWI NACK for wrong Slave address

Question

Hello, 
 
 I am using nRF52832, SDK_15.3.0, S132 SoftDevice and Segger for flashing the image. 
 To understand TWI better, I loaded 'twi_sensor' example as is on nRF52832 development kit where there is no LM75B sensor. 
 
 As per below link, if there is a wrong slave address, there will be NACK. 
 https://blog.digilentinc.com/i2c-how-does-it-work/ 
 
 But I did not receive any interrupt in twi_handler() of event type NRF_DRV_TWI_EVT_ADDRESS_NACK or NRF_DRV_TWI_EVT_DATA_NACK. When will these occur actually. 
 Because of this, code struck in while loop "while (m_xfer_done == false);" 
 
 Thanks & Regards 
 Vishnu Beema

beemavishnu · Accepted Answer

Hello, 
 
 I got the root cause. I added debug print under 'default' case. For wrong address I am getting NRF_DRV_TWI_EVT_ADDRESS_NACK. But this is not printing on terminal because of "while (m_xfer_done == false);" 
 
 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_RX)
 {
 data_handler(m_sample);
 }
 m_xfer_done = true;
 break;
 default:
 NRF_LOG_INFO("twi_default %d", p_event->type);
 break;
 }
} 
 
 Thanks & Regards 
 Vishnu Beema

Why there is no TWI NACK for wrong Slave address

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