https://devzone.nordicsemi.com/f/nordic-q-a/14564/nrf52-sdk11-example-ble_app_hrs_rscs_relay-uart-only-send-the-one-byteYo Man, I use nRF52 with example &quot;ble_app_hrs_rscs_relay&quot; in SDK11. The printf only send one byte and I check other people asked question but still send one byte. So....Is there has any answer. Thanks....a lot Vincenten-USTelligent Community 13Mon, 20 Jun 2016 02:39:23 GMThttps://devzone.nordicsemi.com/thread/55606?ContentTypeID=1Mon, 20 Jun 2016 02:39:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:76ed3324-b707-4127-9aa9-62d36b178e88Vincent<ol> <li>app_uart_fifo intead.c of app_uart.c</li> <li>add app_fifo.c into nRF_Libraries folder.</li> <li>Keil Option for target-&gt;C/C++-&gt;Include Path add fifo ref ..............\components\libraries\fifo</li> </ol> <p>Then Uart/Printf does work on ble_app_hrs_rscs_relay example</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/55605?ContentTypeID=1Mon, 20 Jun 2016 02:34:49 GMT137ad170-7792-4731-bb38-c0d22fbe4515:23af655a-ebb1-4d22-96c2-cbe22e4ec861Vincent<p>Hi Hung Bui, I try to add app_uart_fifo.c switch to app_uart.c and also add app_fifo.c. then UART does work on ble_app_hrs_rscs_relay example.</p> <p>Thank you for your help.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/55604?ContentTypeID=1Fri, 17 Jun 2016 12:41:05 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e37616be-b360-408b-aa7d-4566fd276b62Vincent<p>No, I try it next Monday and let you the result.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/55603?ContentTypeID=1Fri, 17 Jun 2016 10:53:02 GMT137ad170-7792-4731-bb38-c0d22fbe4515:91a710e4-b15e-4cc4-82e2-b13141ee8058Hung Bui<p>@Vincent: Did you use app_uart_fifo intead of app_uart ?</p><div style="clear:both;"></div>