Reflashing Sparkfun Edge to lower baud rate

Development Boards
1

I would like to reflash the Edge board so as to lower the baud rate used during “make bootload” from 921600bps to 115200bps.

Is it possible without the SWD programmer/debugger but only making a new binary and uploading it into the board via Serial Basic Breakout with USB-C?

If yes, how can I do? I am working on Ubuntu 18.04 and already successfully uploaded some SDK examples following the tutorial “Using SparkFun Edge Board with Ambiq Apollo3 SDK” (https://learn.sparkfun.com/tutorials/us … o3-sdk/all).

Thanks in advance

2

Hello - From my current understanding this is not possible. That is to say that the only way to upload a new bootloader is using the SWD interface and a programmer. The bootloader was created by Ambiq Micro, so one might be able to talk to them to get more confirmation.

I think that there are two possibilities:

  1. The bootloader is just a normal program that you could replace with a bootloader of your own. In this case you might find bits on information buried in the SDK that help you figure out how to do so (for example how to re-write the flash memory from within a program – the most important task for a bootloader)

  2. The bootloader is baked-in to the silicon, with a few configuration options. In this case we’ll only ever be able to change those given options. It would take expert help to know if those options can be changed using the bootloader or if they absolutely require a debugger connection.

May I ask why you want to change the speed? I’ve considered this as a possible fix to bootloading problems but it sounds like you have been able to successfully load several examples. That would help me know if this could be a priority for other customers as well - thanks!

3

Thank you very much for your explanation and suggestions, I will try to investigate this further with Ambiq and share information on this forum in case.

The reason why I would like to change the baud rate is indeed some significant instability in bootloading that still remains even after updating the driver with the one in https://github.com/juliagoda/CH341SER (I double checked and it is actually used in place of the old/default one). I guess that one possible reason of such instability could be that 921600bps, so I would like to check if lowering the baud rate would be helpful.