https://devzone.nordicsemi.com/f/nordic-q-a/14701/uart-57600-packet-lossI use the softdevice which is s130.The code is from the demo: static void nus_data_handler(ble_nus_t * p_nus, uint8_t * p_data, uint16_t length) { for (uint32_t i = 0; i &lt; length; i++) { while(app_uart_put(p_data[i]) != NRF_SUCCESS); } /en-USTelligent Community 13Thu, 23 Jun 2016 14:13:00 GMThttps://devzone.nordicsemi.com/thread/56094?ContentTypeID=1Thu, 23 Jun 2016 14:13:00 GMT137ad170-7792-4731-bb38-c0d22fbe4515:72fd6655-e203-4c43-9a4a-4da45ab28454Stefan Birnir Sverrisson<p>Hi Davy</p> <p>When UART data is lost, it is usually either because UART TX buffer is too small or because the BAUD rate is too slow. I suspect the former in your case. Make sure you use app_uart_fifo.c instead of app_uart.c in your project. Try also to make the UART fifo TX buffer larger, defined with UART_TX_BUF_SIZE constant in the ble_app_uart example in the SDK.</p><div style="clear:both;"></div>