Finish testing prototype hardware

[oskirby]

The list of things yet to be tested on the prototype boards before we should start looking into the next revision

• Micro-SD card slot.
• Downstream-Facing USB port detection and power management.
• Downstream-Facing USB port SERDES support (test out https://github.com/enjoy-digital/usb3_pipe)
• Analog-to-Digital converter.
• m.2 PCIe SERDES support.
• Gather noise and current measurements for VCORE and VDDR supplies.
• LiteX support for 2GB memory size.

[oskirby]

So far the microSD card seems to work in SPI mode, and I have been to boot from it using the LiteX BIOS. I have thus far been unsuccessful in getting Linux to detect the cards. The full-width microSD card support in Litex still seems like a work in progress.

[oskirby]

A new commit to the bootloader (oskirby/tinydfu-bootloader@1e0b711) should now enable the DFP port power.

[oskirby]

I've added a test to verify that the ADC works as expected (oskirby/logicbone-tests@b8254bc)