Secure DFU, update from a remote server

[lybrus]

Hi,

I develop a device with a GPRS modem. GPRS modem is controlled by nrf52840 and it is impossible to use two devices for DFU process.

SDK: 17.0.2

SoftDevice: s140 7.2.0

My idea is:

1. Download bin and data files to nrf flash using uart (AT commands) from an HTTP server
2. Set some flag for bootloader
3. Reboot the nrf
4. Bootloader upgrades by checking this flag. Check firmware and activate new firmware (dual-bank update).

Main idea - not to bring all processes about firmware checking to the main application to reduce application size and complexity. So, questions:

• Is it a good idea or not?
• How to store bin and data files to nrf flash?
• How to set flags for the bootloader?
• How to modify the bootloader?

It would be great to have some examples or links to similar posts. Thanks in advance!

[lybrus]

As a start point for the bootloader I'm planning to use /nRF5_SDK_17.0.2_d674dde/examples/dfu/secure_bootloader/pca10056_s140_ble to keep DFU using BLE.

[lybrus]

As I understood, I need to store firmware in my application using nrf_fstorage,(like in nrf_dfu_flash.c) build the bootloader with NRF_BL_DFU_ALLOW_UPDATE_FROM_APP=1 and tell the bootloader to validate the new firmware.

So questions:

• How to get the right address to store firmware? Or I need to write the new firmware to free space and tell the address of the new firmware to the bootloader?
• How to tell the bootloader to validate the new firmware?
• Is it suitable for the softdevice and bootloader update?

[Amanda Hsieh]

Hi Damir, 

Sorry for the delay.

lybrus said:

How to get the right address to store firmware? Or I need to write the new firmware to free space and tell the address of the new firmware to the bootloader?

See Device Firmware Update process and Dual-bank and single-bank updates doc. 

lybrus said:

How to tell the bootloader to validate the new firmware?

Sorry for the delay. Please see the Validation doc.  

lybrus said:

Is it suitable for the softdevice and bootloader update?

 Yes, see Bootloader and DFU modules doc.

 -Amanda H. 

[lybrus]

Hi Amanda,

Thank you for your reply.

As I understood in the application I can:

1. Store init packet using nrf_dfu_validation_init_cmd_create, nrf_dfu_validation_init_cmd_append and nrf_dfu_validation_init_cmd_execute. The last one returns the address to store the new firmware packet.
2. Store new firmware packet using nrf_dfu_flash_store
3. And just reboot the MCU. Bootloader compiled with NRF_BL_DFU_ALLOW_UPDATE_FROM_APP=1, right?

[lybrus]

I've done, dfu works =) But I have a stupid problem with i.3 (reboot the MCU). How to do it correct?

I've tried:

// 1
nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_RESET);

// 2
NVIC_SystemReset();

But it doesn't work. 

If I reboot manually - the bootloader updates firmware.

nrfjprog -r

[lybrus]

Everything is ok. nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_RESET); works. I needed to wait untill nrf_dfu_settings_write_and_backup finish.