NRF52840 and STM32 (firmware update)

[Vasa]

Hi team, there is a connection between NRF52840 and STM32F407 via UART. The task is to provide a possibility to update STM32 firmware via uart (nrf is responsible to perform this task). So, nrf should receive file (.bin) over the air, configure the stm32 bootloader and send the file (.bin) to the stm32. My question is: how to receive firmware file for STM32 over the air?
I tried to use Object Transfer Service (OTS), I use the sample form SDK15.3 (../examples/ble_peripheral/experimental/ble_app_ots/). I load the sample to the devboard NRF52840-DK, but i can't to connect to the service using nRF_Connect scanner. I tried to use 2 devboards as metioned here (https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v15.0.0%2Fble_sdk_app_ots.html) but it is also not working (there is no connection between server and client).

[Vidar Berg]

Hi,

You can receive app images intended for external targets if you enable the NRF_DFU_SUPPORTS_EXTERNAL_APP config option in the bootloader project, and use the -----external-app flag when you create the DFU distribution package. The image will be stored to bank 1. So the remaining task will be to forward it to the ST chip.

Screenshot from the nrfutil help menu (nrfutil pkg generate --help)

Regards,

Vidar

[Vasa]

Thanks for the reply, is it possible to verify that the ST FW received before sending it to the target? I mean how to read ST .hex, were it is stored?

[Vidar Berg]

The bootloader verifies the integrity of the received image in nrf_dfu_validation.c::postvalidate() and updates the .bank_1.bank_code flag to NRF_DFU_BANK_VALID_EXT_APP if it passes the check. Once the bank code is updated, you know the ext. App has been validated, and you can start transferring it to the ST chip.  

nrf_bootloader_fw_activation.c::app_activate() shows how internal app images are copied from bank 1 to bank 0. You may use this as a reference. Except that your function needs to copy it from bank 1 to the ST. 

[Vasa]

I managed to send stm32 .hex (FW intended for ST) over nrf dfu service and check the flag .bank_1.bank_code it is definitely changed to NRF_DFU_BANK_VALID_EXT_APP, but anyway it is not obvious for me how to transfer ST firmware to the ST chip? Where the ST FW located from physical point of view? Is there any example how to do this in a proper way? 

SDK 15.3

Softdevice S140

[Vidar Berg]

The new image is placed in the free area above the application which we call bank 1, see Memory layout and Dual-bank updates.  And you may use nrf_dfu_bank1_start_addr() to get the start address of bank 1. 

The image transfer to the ST part will require a custom implementation as we don't have a reference implementation of this. I suggest using the app_activate() function to get an idea of how the image can read from bank 1 and copied to target. 

[Vasa]

Thanks fo the reply, but what will happen if STM firmware is bigger than bank1 size, will nrf reject to receive this file? Will nrf inform that it is impossible to receive this file?
IMPORTANT! Is there possiblity to receive STM firmware part-by-part and send these parts to STM (on the fly)?