enabaling uart on nrf52840 causes soft device failure

RE: enabaling uart on nrf52840 causes soft device failure

m2800 — Tue, 23 Apr 2019 16:15:02 GMT

The root problem is the inability to write data out the UART from within a GCC Function Instrumentation call. It causes the program to consistently crash in sd_ble_gap_device_name_set(). If I bypass that particular call the program will eventually crash somewhere else. This leads me to suspect SVCALL related functions.

I've tried adding an 'interrupt' attribute to various functions in the the function but tit still crashes.

For now I have to look at alternatives.

RE: enabaling uart on nrf52840 causes soft device failure

Einar Thorsrud — Tue, 23 Apr 2019 15:09:20 GMT

OK. So what is the root problem?

RE: enabaling uart on nrf52840 causes soft device failure

m2800 — Tue, 23 Apr 2019 14:45:35 GMT

Adding the UART did not cause the soft device problem.

The problems were caused by using the UART in the instrumentation functions __cyg_profile_func_enter and __cyg_profile_func_exit.

RE: enabaling uart on nrf52840 causes soft device failure

Einar Thorsrud — Tue, 23 Apr 2019 13:28:07 GMT

Hi,

I do not see any reason why initializing UART should have any effect on the SoftDevice. Do you do anything other than initializing the UART, or is that the only difference? Can you show us code demonstrating both cases?

RE: enabaling uart on nrf52840 causes soft device failure

m2800 — Fri, 19 Apr 2019 15:45:08 GMT

The debugger and logging showed literally *nothing*. One execution run showed the following:

The system is halted.

The debugger displays 'Unknown function at 0x0000978

If I hit GO (F5) the system then displays

<error> app: SOFTDEVICE: ASSERTION FAILED

UPDATE

I've isolated the problem. For main.c, Options, Code Generation, 'Instrument Functions is enabled. I am trying to output data to the UART in the instrumentation calls.

GCC Instrumentation adds a call to __cyg_profile_func_enter and __cyg_profile_func_exit at the entrance to and exit from every function, respectively.

This is the code that was added to test instrumentation:

void main_constructor(void) __attribute__ ((no_instrument_function, constructor));

void main_destructor(void) __attribute__ ((no_instrument_function, destructor));

void __cyg_profile_func_enter(void *, void *) __attribute__ ((no_instrument_function));

void __cyg_profile_func_exit(void *, void *) __attribute__ ((no_instrument_function));

void __cyg_profile_func_enter(void *this, void *callsite)
{
UART_Char_Out('X');
}

void __cyg_profile_func_exit(void *this, void *callsite)
{
UART_Char_Out('X');
}

I haven't check the assembler output yet but it would appear that hardware context is not sufficiently saved and restored. This would account for the different and seemingly random errors.

RE: enabaling uart on nrf52840 causes soft device failure

awneil — Thu, 18 Apr 2019 20:15:35 GMT

Do you have the RTT logs enabled? Do they show any messages?