Update board designs

So I released new board revisions over the past few days, I have done my best initial check on these but I have not yet ordered them to build up. Even if I had ordered them I would still correct any mistakes in new revisions so the files might as well be public.

I am also working on a differential version of the PCM4202 ADC board, I did have a revision 1.0 design but I am not happy with it and so decided to rework this. It should be a more versatile solution than the single ended version and have a better PCB layout.

I also came across Orange Pi SBCs which look very neat with the AllWinner H3 SoC onboard all of them. Early 2015 I had started designing an ADAU1452 Raspberry Pi hat type board, unfinished designs still available at github.com/pwzj/ohdsp.

I stopped working on this as the Pi only support I2S in stereo with no TDM, limiting what I wanted to do with it. The AllWinner H3 SoC datasheet specifies support for all the normal I2S/left and right justified/TDM modes on the audio data lines and so this may work for my original idea. I am very tempted to either spin an ADAU1452 DSP board to interface with this, or make an adapter board to hook into my current DSP design. This all depends on software/driver support for TDM mode, and I need to do a lot more research.