I've recently come into some more time to look at these again. I managed to repair some faults with boards I already had (be careful when playing with shorting pins on the NAND, you can very easily blow up a 6-pin PNP transistor in the power supply section!). I've decided to make a decent effort at porting a new OS. I'm pretty much sick of Linux these days so I'm going with something I find a bit more interesting: Windows Embedded. Specifically Windows Embedded Compact 7 (AKA Windows CE7).

What works - generally

• There is a working EBOOT image with somewhat functional support for the NAND FLASH - enough to store the system configuration, anyway. I still need to strip the FEC drivers out of this, because selecting them will cause the board to freeze when it goes looking for an ethernet controller that doesn't exist. The EBOOT code seems to ignore the BSP_NOETHER flag.
• The EBOOT USB RNDIS download client
• The EBOOT USB Serial download client
• NK USB sync support. This works well enough to be able to use remote zoom-in to see what would be on the device screen, if the LCD driver worked... Unsurprisingly I am stuck at "calibrate display".
• The rest of the things required to get an OS image to boot and run without crashing.

What does not - specifically

• Display - I have a working backlight driver, but I am still fighting the LCD driver. This is priority 1, and I feel like I am fairly close.
• SD Controller - CE throws exceptions when cards are inserted and removed. The OS doesn't crash, but SD doesn't work. The fact that I get anything at all indicates that this is probably pretty close. It's priority 3.
• WiFi - Doesn't work due to the lack of the SD controller support. Bluetooth might work, but I haven't tested it and I don't care enough yet.
• Touchscreen - I don't think this works. The driver is included in the BSP, but touching the screen seems to have no effect on the image obtained by remote-zoom in. This is probably priority 2.
• Audio - The MX51 development kit uses a different codec chip. I will need to write a driver for this before audio will work
• Power button support - currently having this enabled in the BSP causes the board to shut down instantly once it boots. I suspect this is due to a misconfigured GPIO or pin MUX, or the driver is looking in the wrong place. Should be an easy fix.
• NK NAND driver - Should be relatively easy to get the NAND driver from the EBOOT to work for the NK, but I haven't tried yet. Again, should be an easy fix but I am expecting trouble. Tied with the SD controller for priority 3.
• DECT - I haven't even started on reverse engineering this so obviously there's no support. Being an SPI peripheral this should be fairly straightforward to implement - provided that SPI works there's no real hardware work needed for the driver.
• RTC - The OS throws errors about writing to this every few minutes. I suspect this means that CE is not able to remember the time yet. Again, should be an easy fix.

What hasn't been tested at all

• USB Host - I suspect that this might work, but I can't enable it while I am still dependent on the USB Sync connection to work with the device.
• Bluetooth - I don't care about this enough yet.
• Keypad support - I disabled this at the same time as the Power Button driver to work around the issue with the board shutting down once boot had finished.

Conclusion

I expect to get display off of the not working list very shortly. Once that is done the next tasks for me are:

1. Touchscreen
2. NK NAND drivers
3. SD Controller
4. Wireless
5. Audio
6. Bluetooth
7. Keypad
8. Power Button
9. DECT - I am interested in using this as a lightweight, long range data network for my automation and control stuff, which is what the T-Hubs are slated for right now.
10. RTC (maybe - this might be a little higher depending on what happens)