Bootloader via UART without shell

[JuanAlm]

I have a custom board with STM32L4 and nrf52840 micros. I need to upgrade the nrf52 micro with an image saved into the flash of the STM32L4 micro, so I have not a shell just an UART.

I have used the MCUMGR module to upgrade a board connected via USB to a linux pc.

My firmware is programmed with nrf connect sdk 2.2.0.

[Vidar Berg]

Hello,

The STM32L4 must implement the mcumgr and SMP protocol to transfer the FW image to nRF52 target. Documentation for these protocols can be found here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/2.5.2/zephyr/services/device_mgmt/mcumgr.html.  

Best regards,

Vidar

[JuanAlm]

Thansk for the fast reply!

I checked it and now I understand better. Anyway I have some questions. The SMP client has to be on the STM32 micro and the server on the nrf52 micro, but I cant find a client SMP sample for UART. I just found this repository with a SMP client for BLE  but it says in the step 6 and 7 that a button has to be pressed.

So i have the next problems:

1º) I cant find a SMP client for UART

2º) I have not buttons availables to press on my custom board.

[Vidar Berg]

Unfortunately, I am not aware of any SMP client implementation that can be used directly. However, it should be possible to use many of the components already available in the SDK to create your own module.

JuanAlm said:

2º) I have not buttons availables to press on my custom board.

This is not needed if your application can receive SMP commands.

[JuanAlm]

My questions now is:

1º) Why I need SMP protocol on the STM32 micro side?

2º) Can't I use directly mcumgr on both micros?

3º) Where can I find the diagram/step by step to use the smp/mcumgr protocol from the STM32 micro side? I can't find smp or mcumgr modules for STM32 sdk.

Sorry but this is a mess for me. Thanks for your support!

[Vidar Berg]

JuanAlm said:

1º) Why I need SMP protocol on the STM32 micro side?

Both sides need to have a common protocol for how the FW image should be transferred over the serial interface. You could always implement another method to handle the FW update, but that would require a custom solution.

JuanAlm said:

Can't I use directly mcumgr on both micros?

mcumgr is a command line tool that can be run on Linux, macos, or Windows. It cannot be used on a 'bare-metal' target.

JuanAlm said:

3º) Where can I find the diagram/step by step to use the smp/mcumgr protocol from the STM32 micro side? I can't find smp or mcumgr modules for STM32 sdk.

I only know what's available in Zephyr/nRF Connect SDK. SMP and MCUmgr client implementations can be found here: https://github.com/zephyrproject-rtos/zephyr/tree/0014f3dc4dda0142561b6495fc9213a4eacf8c27/subsys/mgmt/mcumgr/grp 

[JuanAlm]

Im looking SMP client and it looks quite difficult to adapt to FreeRTOS (RTOS im using in my STM32 micro). So if I understand it good:

1º) SMP is for controlling the bootloader?

2º) Bootloader there are 2 options, MCUBoot and nRF Secure Immutable Bootloader, right?

3º) Would it be easier to code it myself something to comunicate directly with the bootloader instead of adapting SMP to FreeRTOS?

Respect my last question I have found this:

 DFU without mcumgr and SMP server 

Any advance in this respect?