Application merged with bootloader causing read back protection, how to get rid of read back protection while doing so

RE: Application merged with bootloader causing read back protection, how to get rid of read back protection while doing so

Einar Thorsrud — Wed, 15 Nov 2023 09:19:55 GMT

Hi,

What you describe here should work, and when I test on my end with your approtect_hw_disable() function and the same nrfjprog commands I am able to read back afterwards. Can you check if you have ENABLE_APPROTECT defined in your project? (If you do, the debug interface will stay locked down regardless of what is in UICR).

RE: Application merged with bootloader causing read back protection, how to get rid of read back protection while doing so

Gaurav — Tue, 14 Nov 2023 06:19:56 GMT

Yes the application is built on SDK 17.1.0 and the commands used to program the device is -

nrfjprog --recover
nrfjprog --program %merged_hex% --chiperase --verify --reset

And in the application we have used :

void approtect_hw_disable(void)
{
    if ((NRF_UICR->APPROTECT & UICR_APPROTECT_PALL_Msk) 
       == (UICR_APPROTECT_PALL_Msk))
    {
        NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Wen << NVMC_CONFIG_WEN_Pos;
        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
        NRF_UICR->APPROTECT = (UICR_APPROTECT_PALL_HwDisabled << UICR_APPROTECT_PALL_Pos);
        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
        NRF_NVMC->CONFIG = NVMC_CONFIG_WEN_Ren << NVMC_CONFIG_WEN_Pos;
        while (NRF_NVMC->READY == NVMC_READY_READY_Busy) {}
        NVIC_SystemReset();
    }  
}

RE: Application merged with bootloader causing read back protection, how to get rid of read back protection while doing so

Einar Thorsrud — Mon, 13 Nov 2023 13:46:22 GMT

Hi,

Read back protection is enabled by default on the latest generation of the nRF52840, so it must be explicitly disabled both by hardware (controlled by UICR) and software (see Access port protection). Which exact set of commands to you use to program your device? And is the application built with SDK 17.1.0 (or an updated MDK if using an older SDK, ref IN141)?

The tools we provide are designed to make this simpler, so if you first recover using "nrfjprog --recover" this will open the debug port in the UICR and writ a small firmware that opens the debug port. When you subsequently write your firwmare, this must also be built to open the debug port (which it does by default in SDK 17.1.0). And with that, you will be able to read the flash after programming. If that does not work, either the UIRC does not contain the magic word or the firmware does not write the magic word runtime (which it does by default) or both, and then we need to look more closely at that.