https://devzone.nordicsemi.com/f/nordic-q-a/17633/nrf_drv_twi_tx-return-nrf_error_busyHi, I am using the following function to read the content of a register: static ret_code_t read_reg(uint8_t slave_address, uint8_t register_address, uint8_t *value) { ret_code_t err_code; err_code = nrf_drv_twi_tx(&amp;m_twi, slave_address, &amp;register_addressen-USTelligent Community 13Thu, 10 Nov 2016 12:07:59 GMThttps://devzone.nordicsemi.com/thread/67809?ContentTypeID=1Thu, 10 Nov 2016 12:07:59 GMT137ad170-7792-4731-bb38-c0d22fbe4515:638439ba-2896-4fb8-a7cf-1c544abb6b49Keton<p>show us your TWI init function. If you supplied TWI handler nrf_drv_twi_X functions will become non blocking and you&#39;ll have to manually handle waiting for end of the transfer. If you fail to do so you&#39;ll get NRF_ERROR_BUSY. Solution is either to specify NULL as TWI event handler and get blocking behavior from nrf_drv_twi_X or use app_twi which will handle all this for you and allow easy mixing of blocking and non blocking calls.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/67810?ContentTypeID=1Thu, 10 Nov 2016 12:02:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:1ac6fe7f-d36b-4e22-9fb3-eca5336eb16bStian R&#248;ed Hafskjold<p>Are you sure the TWI slave is ACKing the transmission?</p><div style="clear:both;"></div>