Flash corruption caused by power down during writing

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Mon, 05 Oct 2020 12:17:55 GMT

Let's continue here.

RE: Flash corruption caused by power down during writing

ivnn — Mon, 05 Oct 2020 08:48:43 GMT

I found an interesting condition it's happened if I have flashed bootloader

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Fri, 15 May 2020 14:11:48 GMT

Hi,

Yes, flash writing is prevented when there is a POF warning condition. This is a bit odd though since it will look like the flash write operations succeed, but in fact, nothing is written to flash.

RE: Flash corruption caused by power down during writing

ivnn — Fri, 15 May 2020 14:04:52 GMT

Could POF warning help to block writing during power below threshold?

// Initialize SoftDevice.
err_code = sd_softdevice_enable(p_clock_lf_cfg, softdevice_fault_handler);
if (err_code != NRF_SUCCESS){
return err_code;
}
err_code = sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);
APP_ERROR_CHECK(err_code);
err_code = sd_power_pof_enable(1);
APP_ERROR_CHECK(err_code);
err_code = sd_power_pof_threshold_set(NRF_POWER_THRESHOLD_V28);
APP_ERROR_CHECK(err_code);

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Fri, 15 May 2020 13:54:33 GMT

I don't have a specific recommendation, but you should consider this in your particular case. The point is that ending up in a loop with rapid writes to flash is bad, and should be avoided. That is a general thing that is not particular to the nRF.

RE: Flash corruption caused by power down during writing

ivnn — Thu, 14 May 2020 12:18:16 GMT

What time delay you can recommend to wait for stabilize nrf52 after powerup ?
thx for reply!

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Thu, 14 May 2020 11:55:01 GMT

Hi,

Not in general, but it is not a good idea to write to flash immediately after a reset since that could cause the device to go in a loop where it resets, tries to write to flash and get a power failure leading to a reset etc. if the battery is depleted.

RE: Flash corruption caused by power down during writing

ivnn — Thu, 14 May 2020 11:12:08 GMT

Hi,

I have the same one problem, when I power up or perform power reset nrf52832 some times I have corrupted flash content.

Am I right I should add some code delay after powerup and before main code start?

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Fri, 22 Mar 2019 11:58:07 GMT

No, that is not possible.

RE: Flash corruption caused by power down during writing

Andrea Pieretti — Fri, 22 Mar 2019 11:24:09 GMT

ok thanks,

Now I see that, if the power loss occours during a flash erase, the NRF_EVT_POWER_FAILURE_WARNING event inside the SoC raises only after the erase complete.

The SDH_SOC_OBSERVER has already priority 0.

Is it possible to catch the NRF_EVT_POWER_FAILURE_WARNING during an erase operation?

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Fri, 22 Mar 2019 09:41:25 GMT

[quote userid="76761" url="~/f/nordic-q-a/45189/flash-corruption-caused-by-power-down-during-writing/177759"]How can avoid this issue for the SDK Mesh Flash Writes (for example, during the provisioning and subscribe/publish configuration phase from the provisioner)?[/quote]

Usig POFWARN will prevent all flash writes. This is implemented in HW. From product specification:

If the power failure warning is enabled and the supply voltage is below the threshold, the power-fail comparator will prevent the NVMC from performing write operations to the flash.

RE: Flash corruption caused by power down during writing

Andrea Pieretti — Fri, 22 Mar 2019 08:59:27 GMT

Ok, now i'll take care of time margins during flash write.

I'm implementing a BLE Mesh Network using BLE Mesh SDK 3.1.0.
I use the "flash_manager" API to write my user persistent data and I see that these APIs do defragmentation and other smart procedures to manage the flash area.

If there's a a power down during a write session, I've noted that the SDK throw an assert at the next power on:
- mesh_config_backend_file_create
- flash_manager_add
- get_invalid_bytes
- get_next_entry [ NRF_MESH_ASSERT(p_entry->header.len_words != 0);]

Now I'm trying to avoid this flash corruption using the POFWARN event for my persistent user data writes.

How can avoid this issue for the SDK Mesh Flash Writes (for example, during the provisioning and subscribe/publish configuration phase from the provisioner)?

I've no control in these phases, and a flash memory corruption at the final customer should be critical and irrecoverable.

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Fri, 22 Mar 2019 07:47:33 GMT

Hi,

This makes sense.

[quote userid="76761" url="~/f/nordic-q-a/45189/flash-corruption-caused-by-power-down-during-writing/177671"]Is this sufficent to avoid flash corruption during power down writes?[/quote]

This will make sure that no writes are allowed to flash after the supply voltage has dropped below the POF warning level. However, weather the flash is corrupted or not also depends on the time it takes from the POF warning until VDD drops below the minimum voltage, in cases a flash write operation was already started before the POF warning. This might be theoretical but could occur if for instance the device starts to draw more current while writing to flash, pulling down the battery voltage. Therefor you should probably add some margin.

RE: Flash corruption caused by power down during writing

Andrea Pieretti — Thu, 21 Mar 2019 17:18:10 GMT

I've found this method which uses only SoftDevice APIs

I call the sequent code after SoftDevice enable.

ret_code_t err_code = sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);
APP_ERROR_CHECK(err_code);
err_code = sd_power_pof_enable(1);

APP_ERROR_CHECK(err_code);

err_code = sd_power_pof_threshold_set(NRF_POWER_THRESHOLD_V28);
APP_ERROR_CHECK(err_code);

Now I'm able to catch the NRF_EVT_POWER_FAILURE_WARNING event inside the SoC event observer.

Is this sufficent to avoid flash corruption during power down writes?

RE: Flash corruption caused by power down during writing

Andrea Pieretti — Thu, 21 Mar 2019 15:54:21 GMT

ret_code_t nrf_drv_power_init(nrf_drv_power_config_t const * p_config)
{
#ifdef SOFTDEVICE_PRESENT
 if (m_initialized)
 {
 return NRF_ERROR_MODULE_ALREADY_INITIALIZED;
 }
 if (nrf_sdh_is_enabled())
 {
 return NRF_ERROR_INVALID_STATE;
 }
#endif
 if (p_config == NULL)
 {
 p_config = &m_drv_power_config_default;
 }

 ret_code_t err_code = nrfx_power_init(p_config);
 if (err_code == NRFX_SUCCESS)
 {
 m_initialized = true;
 }
 return err_code;
}

This is the code of nrf_drv_power_init: if the softdevice is already enabled, the function return with NRF_ERROR_INVALID_STATE error code

There is something not clear to me

RE: Flash corruption caused by power down during writing

Einar Thorsrud — Thu, 21 Mar 2019 13:16:30 GMT

Hi,

You are right that using POFWARN make sense in this setting, as flash writes are not allowed after a POF warning.

You cannot use nrfx after the SoftDevice has been enabled, as it uses direct register access to the protected POWER registers. You could use the power driver (nrf_drv_power) instead after first enabling the SoftDevice, as this use SoftDevice API's when a SoftDevice is present.

Similarly, you cannot write to POWER->DCDCEN when the SoftDevice is enabled, as this is a protected peripheral. Instead you should use the SoftDevice API for this (sd_power_dcdc_mode_set()), or simply set POWER_CONFIG_DEFAULT_DCDCEN to 1 in sdk_config. h and use nrf_drv_power.