When I recently built a custom board featuring Edison, I discovered that during the boot process the drive strength on UART2_TX changes.
At first it starts out with a strong drive strength but after passing control to the bootloader (uboot I think) it changed to weak.
This caused trouble with the level shifters I was using as the "pull up" strength on the RX line to the host (Edison's TX line) was strong enough to trick the level shifter (TXB0108PWR) into thinking the data direction had changed, and form the point on nothing could be received from the UART.
In the process of debugging this it struck me that I can't really find an authoritative document on the boot process for Edison.
I think a good low-level description of the boot process would be very helpful for system designers.
Does anyone know of where I could find such a document?
- Intel Atom®
Thanks for your interest in the Intel Edison Platform.
I appreciate that you start this discussion, I'm afraid that at the moment there is no document available for the boot process of the Edison. I will communicate to the Department in charge, the need of such document for system designers such as yourself.
I encourage you to document your results and share them with the community, since it may benefit other users.
I leave this links here, since it might be useful:
2) https://github.com/01org/edison-u-boot GitHub - 01org/edison-u-boot
Have a nice day!
Thank you, Jose.
Those links are very useful. I will update this thread with anything I find.
I also found a document describing the minimum boot requirements for Atom - but it's a bit too low level for using Edison.
Here is a link to it: https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwj9mvHywf... Minimal Boot Requirements for the Intel® Atom™ Processor E6xx Series
I hope that is useful too!