A simple BLE-less UART example not working on nRF51822

RE: A simple BLE-less UART example not working on nRF51822

Nelson Rodriguez — Fri, 16 Jun 2017 20:55:11 GMT

Hi i use DTR and RTS in my serial port monitor (Hercules) and it works fine,....

RE: A simple BLE-less UART example not working on nRF51822

diode — Tue, 21 Apr 2015 16:42:28 GMT

That makes sense. Thanks for your help!

RE: A simple BLE-less UART example not working on nRF51822

Susheel Nuguru — Tue, 21 Apr 2015 10:35:25 GMT

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

RE: A simple BLE-less UART example not working on nRF51822

Susheel Nuguru — Tue, 21 Apr 2015 10:07:16 GMT

I see that what you said, I just looked into POWER->RESETREAS to see why that is caused by the SYSRESETREQ by ARM. I will find out more about that and post you later.

RE: A simple BLE-less UART example not working on nRF51822

diode — Tue, 21 Apr 2015 06:06:37 GMT

No, I was not doing anything extra other than the code in that link. But my previous description might be a little misleading. After I pressed "q", there would be nothing after "Exit..." if I didn't input anything. However, as long as I typed in another character, the program will print "Start:".

RE: A simple BLE-less UART example not working on nRF51822

Susheel Nuguru — Tue, 21 Apr 2015 06:00:24 GMT

Hi diode,

It is not normal to have a reset after pressing 'q'. If you are sure that the reset is happening after same amount of time after pressing 'q', then there seems to be some kind of unhandled exception triggered. Are you sure you are doing nothing more than the example you linked here?

RE: A simple BLE-less UART example not working on nRF51822

diode — Mon, 20 Apr 2015 18:48:52 GMT

Hi Aryan. It turns out the it was because of the serial monitor was using open-drain mode so that it could not pull the line high. After switching it to normal mode (can pull the line high), I can see the loopback testing work on my serial command. Another small question: after hitting "q" the program will enter a infinite loop state. However, it gets itself out in a second or so and print out "Start:" (meaning a reset). Is this behavior expected because of something else (e.g. watchdog)?

RE: A simple BLE-less UART example not working on nRF51822

Susheel Nuguru — Mon, 20 Apr 2015 07:58:39 GMT

sorry, I missed to see that it is happening repetitively A Note though your Start cannot happen repetitively as this is outside the loop. Seems like a reset happening somewhere, I cannot understand where and why.

RE: A simple BLE-less UART example not working on nRF51822

diode — Mon, 20 Apr 2015 06:52:20 GMT

Regarding your second comment, my serial monitor was not configured to have flow control. And even if I have something left in TX buffer, it should be depleted after a few runs. But I kept seeing those characters. Those were so bizarre to me since it was such a simple application.

RE: A simple BLE-less UART example not working on nRF51822

diode — Mon, 20 Apr 2015 06:52:16 GMT

Thanks for your reply. I reflashed the code without SoftDevice, and now at least it behaved similarly (and abnormally) as the one with SoftDevice. For your first comment, even if somehow my serial monitor was sending something to trigger the while loop, I shouldn't see "Start:" over and over in my serial monitor, since that string printf was outside the while loop. I tried the Jlink debugger and set breakpoints in "while(app_uart_get(&cr) != NRF_SUCCESS);" and " while(app_uart_put(cr) != NRF_SUCCESS);". I kept hitting F5 and could see the input characters I typed bounced back to my serial monitor (which was something I should expect). However, as long as I removed the second breakpoint, I couldn't see the same behavior. Also, every time I typed in "Return" key to the serial monitor in debugging session, I saw "Start:" which shouldn't there.

RE: A simple BLE-less UART example not working on nRF51822

Susheel Nuguru — Mon, 20 Apr 2015 05:17:09 GMT

Hi Diode,

If the same code starts with softdevice then it should work fine without it if you have set the IROM and IRAM addresses accordingly. With your example softdevice does nothing but jump correctly to you application. you can try to debug the code without softdevice to see if your main is being executed.
May be your serial monitor is configured to have flow control and It is possible that you have typed something on serial emulator before starting your application which was in the emulator TX buffer waiting to be transmitted (as nothing on the other side is ready to receive). As soon as you flashed your board, your app received that char and moved out of waiting.

also if you want to have 1000ms wait in between Start and Hit, you need to swap this lines

                        printf("Hit.\r\n");
                        nrf_delay_ms(1000);