Flash operations do not work in the hard fault handler (HardFault_c_handler function).

[ilyasbsran]

Hi,

I want to log the error type and program counter when a hard fault occurred. I implemented some algorithm for that, I am using fds library for saving this information to flash. I do not get an error when saving hard fault information on the flash. 

How can i save hard fault information to the flash?

[Kenneth]

Hello,

I guess there are different ways, but considering you are in the hardfault handler and you can't really depend on any software modules to work, and the interrupts are disabled (or lower priority), so you would need to use flash api that are bare metal and don't rely on interrupts or other software modules. In that case I suggest to use the api in \modules\nrfx\hal\nrf_nvmc.c directly, for instance call nrf_nvmc_page_erase() to erase the flash page you want to store the information, and then follow by one or several calls to nrf_nvmc_write_words(), before you do a system reset to start the chip again. It may be that you need to rename the api in \modules\nrfx\hal\nrf_nvmc.c, because you may using a similar api in your project already that rely on other software modules.

Kenneth

[Vidar Berg]

Also have a look at this post if you are using the Softdevice in your application:  RE: Disable Softdevice sandboxing in fault handler  

[ilyasbsran]

NRF_MWU->PREGION[0].SUBS &= ~(MWU_PREGION_SUBS_SR30_Include << MWU_PREGION_SUBS_SR30_Pos);
__DSB(); // barrier to ensure register is set before accessing NVMC.  

I used it at starting of HardFault_c_handler() function. 

[Vidar Berg]

Have you confirmed through debugging that flash_set_data() ends up being called in HardFault_c_handler()?

[ilyasbsran]

Yes, I confirmed it, I check it by printing log via j link rtt

[Vidar Berg]

Thanks for confirming. What do you see when you read the memory at 0x76000 afterwards?

[ilyasbsran]

I see the same value every time.

I erased flash using nrfjprog. then I run this code. I see the same value (it was 0 )every reset.

#define ADDRESS_OFF_TEST                    0x45000

void flash_set_data(const uint8_t * src){
    nrf_nvmc_write_bytes(ADDRESS_OFF_TEST, src, sizeof(uint8_t));
}

void flash_get_data(uint8_t * dst){
    memcpy(dst, (uint8_t*)ADDRESS_OFF_TEST, sizeof(uint8_t));
}
int main(void)
{
    nrf_delay_ms(10000);

    uint8_t  buffer[1];
    flash_get_data(buffer);

    BB_printf(LOG_FATAL, "Counter : %u", buffer[0]);

    buffer[0] = buffer[0] + 1;
    flash_set_data(buffer);

    nrf_delay_ms(10000);

    NVIC_SystemReset();
}

I think my problem is not about enabling or disabling the soft device.

FDS_BACKEND 1 in sdk_config.

[Kenneth]

Can you erase the page and also change to:

buffer[0] = buffer[0] - 1; // - instead of +

And share what you get then?

Kenneth

[ilyasbsran]

When I erase the page before writing it works. it was not about increasing or decreasing the buffer. I don't understand why it is related to erasing the page.

[Vidar Berg]

With a flash write operation you can only flip bits from '1's to '0's. To get the bits back to '1' you need to erase the flash page.