A simple BLE-less UART example not working on nRF51822

[diode]

I am trying to do a simple UART test with nRF51822 without BLE functionality. The code is a simplified version of the UART example in nRF51 SDK, and can be found here . It is really not much there: it sends the data from RX back to TX; if it gets a 'q' or 'Q', it just quits. I use an external serial monitor (Bus Pirate) to interact with it. However, two strange things happen:

1. If I compile it without SoftDevice (and ROM address starts with 0x00000), I can see nothing from my serial monitor, no matter what I type in.

2. If I compile it with SoftDevice 8.0.0 (although it doesn't use any BLE functions, and ROM address starts with 0x18000), I can repetitively see "Start:" and "Hit.", even I type in nothing in my serial monitor, and there is no 1000ms delay in the between. It is strange because a) "Start:" is not part of the while loop and should only be printed out once in the beginning; b) If "Hit." means the while loop is executed, there should be 1000 ms delay.

Can anyone advise what I am missing in such a simple UART program?

[Susheel Nuguru]

The reason is that you have only one byte reserved for RX buffer. and after exit when you type two characters without doing app_uart_get then the uart fifo library would return with an error, which is handled in your application by function uart_error_handle. The default behaviour would be system reset of you do not handle these errors by overwriting the function app_error_handler

[diode]

That makes sense. Thanks for your help!