Creating a professional Firmware update scheme for STM32

[tam]

I'm working with a commercial-grade food-service product that uses the STM32L073 in conjunction with an android tablet connected over UART or Bluetooth. For our next-gen product, we're investigating methods to economically implement firmware updates on a fleet of a few thousand units. The one major factor is that we have limited resources (one part-time firmware developer with no filesystem or bootloader experience, along with a part-time electrical engineer), so maximizing implementation speed is key. We have the following options we are exploring for firmware updates:

1. Currently the only method implemented to perform firmware updates is using a ST-Link Programmer. Our issues with this setup is that:

• requires the user open up the product
• requires the user plug the ST link onto the pcb (electrically risky)
• Requires a laptop
• ST-Link can be lost
• anyone can flash unofficial firmware

2. Switch to an STM32WB:

• Seems to require either a laptop or phone with the propriety ST app
• anyone can flash unofficial firmware
• Requires porting firmware/pcb to STM32WB

3. Switch to Golioth IoT Platform (replace the ST board)

• Requires porting code to new platform
• Requires fleet management
• Expensive

4. Flash Drive:

• Requires bootloader / file system implementation for which I've struggled to find examples. Presumably requires a significant amount of development time.
• anyone can flash unofficial firmware

5. SD card:

• Requires bootloader / file system implementation for which I've struggled to find examples.
• SD card readers are less common than usb ports.
• anyone can flash unofficial firmware

Which of these 4 options would you recommend committing to for this next generation product, and what resources can I refer to help understand the implementation? Thanks!

[Pavel A.]

> we have limited resources (one part-time firmware developer with no filesystem or bootloader experience, along with a part-time electrical engineer)

You can try to find help for your project here. 

Also, instead of owning a laptop and other equipment, you can rent it.

[Tesla DeLorean]

Surely a boot loader written with some thought can authenticate the firmware image so random/unofficial firmware don't get loaded. There's a) encryption, and b) public/private elliptical curve signing methods that will fit in STM32

Not sure of the SDIO and USB-HOST type support in L07x parts.

Delivery via chip/dongle that plugs in the device is something that's viable. Cheap/simple stand-alone flasher.

[Pavel A.]

Simple micro-SD adapter with UART interface, a.k.a "Openlog Serial Data Logger".

on ebay (and many similar) 

STM32 can use this to read files from a SD card. The UART connector has to be designed. It is slow (~ 115200) but dirt cheap and easy to program.

[Tesla DeLorean]

The OpenLager uses an STM32F411 (512KB Flash)

https://store.myairbot.com/openlager.html

https://newbeedrone.com/products/newbeedrone-f411-openlager

https://github.com/d-ronin/openlager

For pushing updates via AN3155 (STM32 UART Protocol Loader) one can take a look at the update mechanism in the Arduino MKR WAN1300 github repo

[Pavel A.]

The OpenLager firmware on github looks like only logger.

Many openloggers sold on ebay have the sparkfun firmware, it can read existing files from SD and has many interesting options.

[Tesla DeLorean]

Well the d-Ronin guys haven't touched it in 8 years, but the hardware can be disabused to other applications, and the firmware for them delivered as a .BIN.

Yeah the software's not feature rich, but it's designed for very high speed data streams and uses 4-bit SDIO w/DMA

GHI Electronics had some ALFAT related products.  https://docs.ghielectronics.com/hardware/filesystem/intro.html

[waclawek.jan]

>  STM32L073 in conjunction with an android tablet connected over UART or Bluetooth

So, can't the update be delivered from that tablet via the UART connection? Isn't the Bluetooth just a BT-to-UART module connected to STM32 via UART too?

If both answers are yes, then on STM32 side it's the same problem set as with any UART-based bootloader, and we can then discuss them as such; and then you would also need to provide the software counterpart on the tablet side.

JW

[Pavel A.]

Bluetooth UART (HC-05 or newer BLE BM-70) is a viable idea. But wireless may need extra certification effort and security considerations.

[waclawek.jan]

As I understand it, it's already part of the product (although I don't know in what way exactly).

JW