As for the APUs. The vendor (PC Engines) happily provides
PDFs and schematics for their boards:
<https://www.pcengines.ch/pdf/apu1.pdf>
<https://www.pcengines.ch/schema/apu1c.pdf>
<https://www.pcengines.ch/pdf/apu2.pdf>
<http://pcengines.ch/schema/apu2c.pdf>