I have managed to put it into USB boot mode so it can boot linux from an USB stick.
To do this you have to put a 10KOhm resistor across R91.
CPU datasheet can be found here:http://www.nuvoton.com/resource-files/N3290xDataSheetrevisionA5.1.pdf
(Pinout at 3.4)
Also we have a ridiculus amount of Flash memory: 1 Gigabit (128 MB).
Datasheet here: http://www.hynix.com/product/filedata/fileDownload.do?seq=4176
However it does not seem like the bootloader responds to anything sent over serial, so I fear this is the end of the road (for now from this side).
I have no idea how to get the bootloader to do anything more than to try to boot from USB, there is absolutely no documentation on it and I am not able to get it's source code nor can I actually dump the bootloader. I would not be surprised if it actually resides in a mask rom in the CPU.
I am not going to put uboot on it for a couple of reasons:
- If I brick the controller I will have to pay another 160€, which I just can't spend atm (or learn to use my JTAG, but then I would still have nothing to copy back)
- Getting uboot to work will require a lot of work, however somebody else has actually started to work on uboot on this CPU and it might work)
- Nobody without a JTAG is most likely going to be able to flash uboot. While USB boot is there I have no clue if this would somehow make us able to install uboot from a usb stick. And even then would you have to put a 10KOhm jumper across the two pins.
Now we should focus on finding a way of mounting the flash chip from Linux and getting access to the boot loader configuration from there.
Or we could work on the translations some more.
Any input from you, fellow modders?