no HardFault on nRF51

RE: no HardFault on nRF51

Amanda Hsieh — Tue, 04 Feb 2020 08:11:14 GMT

Hi,

Please kindly create a new support case for another issue. This will be easy for users to find a solution to the issue. Thanks.

-Amanda H.

RE: no HardFault on nRF51

Tamas Selmeci — Fri, 31 Jan 2020 13:09:33 GMT

Another issue: there's a function like this to generate random numbers:

static void bsp_rng_read_custom_length_do(uint8_t *output, uint32_t len)
{
#ifdef SOFTDEVICE_PRESENT
    uint8_t avail = 0;

    while (avail < len) {
        if (sd_rand_application_bytes_available_get(&avail) != NRF_SUCCESS) {
            memset(output, 0, len);
            return;
        }
        if (avail >= len)
            break;
        vTaskDelay(pdMS_TO_TICKS(1));
    }
    if (sd_rand_application_vector_get(output, len) != NRF_SUCCES)
        memset(output, 0, len);
#else   /* SOFTDEVICE_PRESENT */
    /* IMPLEMENT */
#endif  /* SOFTDEVICE_PRESENT */
}

If this is executed many times in loop in a task, HardFault occurs. Sometimes the LEDs switch on (as expected, as HardFault_process(...) does so), but sometimes don't. Watchdog resets. Can you reproduce it?

Isn't my 51822 QFACA1 incompatible with the SDK/SoftDevice?

RE: no HardFault on nRF51

Susheel Nuguru — Fri, 31 Jan 2020 12:23:21 GMT

not sure why you did not get a hardfault, but trying what you did I can see that it can break into the hardfault handler

RE: no HardFault on nRF51

Tamas Selmeci — Fri, 31 Jan 2020 10:40:17 GMT

You're right, I obviously was wrong, no execution in the parent context is allowed to occur once vTaskStartScheduler is called.

#define HARDFAULT do { \
    uint32_t *ptr = (uint32_t *)0xABADC0DE; \
    *ptr = 0x12345678; \
} while (0)

By the way, anywhere in any FreeRTOS task the call of HARDFAULT causes the machine to hang, reset by watchdog, but the HardFault_Handler doesn't seem to be called, because that handler should light two LEDs. And the same handler works perfectly if issued before vTaskStartScheduler.

As the address of HardFault_Handler is burnt into the flash, it can't be changed in runtime, so at the moment my best idea is that somehow FreeRTOS disables HardFault_IRQ, but I haven't seen any traces of it... or messes with NVIC...

RE: no HardFault on nRF51

Susheel Nuguru — Fri, 31 Jan 2020 10:13:35 GMT

The vTaskStartScheduler should not be able to mask the HardFault_Handler.

If I understand correctly, the exact same code after vTaskStartScheduler o n nRF52 generates hardfault?

Not sure if this is even possible.

On the second thought, I am assuming that when you say that you put the code that generates hardfault after vTaskStartScheduler , I am assuming that you do that in some task. Because the line after vTaskStartScheduler is never executed in the main() function. The moment vTaskStartScheduler is called, the RTOS scheduler takes over and the control never reaches to the next line of of vTaskStartScheduler inside main. Maybe this is what you are seeing?

RE: no HardFault on nRF51

Tamas Selmeci — Fri, 31 Jan 2020 08:35:51 GMT

The chip is nRF51822 QFACA1 (1810DH). The SDK-12.3.0 (d7731ad) release notes says that SoftDevice-2.0.1 is compatible with nRF51 revision 3 only. I'm not completely sure that my nRF51 chip is rev3... could anyone confirm it?

RE: no HardFault on nRF51

Tamas Selmeci — Thu, 30 Jan 2020 11:39:12 GMT

I've dug into this a little deeper... it appears that with the above code I can successfully generate a HardFault anywhere until the point where vTaskStartScheduler is called. From there the HardFault_Handler doesn't get called. Or no HardFault is raised, although it doubt it...