Thursday, February 26, 2015

U-Boot Update

I've set up a way to build the project without having Crochet involved in building U-Boot. Unfortunately, I'm running into an issue. U-Boot drops me directly into the U-Boot shell but I'm unable to use my USB keyboard.

First things first, I disabled net booting. Removing func(PXE, pxe, na) \ and func(DHCP, dhcp, na) from uboot/include/configs/rpi.h disables net booting. I removed this since I'm only booting from the SD card in the RPI.

The README in uboot/ shows that USB Keyboards can be used inside the U-Boot environment. However, there's not a list of devices supporting USB Keyboards so I assumed that they worked on all devices. That was not the case.

U-Boot USB Keyboard support for the Raspberry Pi is currently under development by Stephen Warren. According to a recent commit he is having trouble getting U-Boot's drivers to work with USB Keyboards.

Since the GPS device uses the Raspberry Pi's GPIO slot, I'm going to disable serial input and output in uboot/include/configs/rpi.h by removing "serial," from "stdin=serial,lcd\0" \ "stdout=serial,lcd\0" \ "stderr=serial,lcd\0". The GPS's communication will not get interpreted as commands for the U-Boot prompt.

Since I'm removing the ability to interact with the U-Boot prompt, I'm going to use Oleksandr Tymoshenko's approach. This involves setting up environment variables and using CONFIG_BOOTCOMMAND. Since the memory layout is the same as Oleksadr Tymosheko's, I'm going to see if his boot commands will work.

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