https://devzone.nordicsemi.com/f/nordic-q-a/26153/close-buffer-fifo-rx-uarti use ble_uart example nrf51 in sdk1 with ic kline interface with mortorbike NRF51 Tx,RX connect to TX,RX MC33290 and Kline of MC32290 connect to motorbike ( you can Google MC33290) specially,byte that NRF transmit in Tx,will be stored in RX. exampleen-USTelligent Community 13Tue, 24 Oct 2017 07:38:34 GMThttps://devzone.nordicsemi.com/thread/103047?ContentTypeID=1Tue, 24 Oct 2017 07:38:34 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8e4a3ad2-af10-4035-877c-b19ad2662e82Sigurd<p>Hi,</p> <p>You could use <code>app_uart_flush()</code> to flush the RX and TX FIFO buffers.</p> <p>Is the MC33290 sending back the data you sent? If so, then you know what data you sent, and can filter/ignore that data, or do some check that it have actually received the correct data you sent. That could be a better solution.</p><div style="clear:both;"></div>