#shuttle is the best place for discussion. But my understanding is there will be a few pads available for custom circuitry. The exact amount and details haven't come out yet but I suspect they will be bare pads. Digital and analogish stuff might be able to go through the RISC-V pads and multiplex.

Thanks, I'll bug the folks in #shuttle. What I really need is to provide custom clock waveforms, so I need input pads that I can drive externally from a custom source (or waveform generator during prototyping). If the RISC-V test harness wants to drive those same pads then that could be a problem unless I can turn off or tristate whatever is trying to drive them.

What do you need to just generate those waveforms from the RiscV?

You can't; they're analog waveforms.

let me correct that... RiscV + ADC + DAC

A more complex pad can easily be made into a bare one. Is there a feature / person here which/who curates a circuit-level "job jar" or list of desired "stuff" w/ progress and commentary?

@Troy Benjegerdes - OK, so if enough DACs are available (we need at least eight), then we could theoretically get by with the harness for mock-up purposes only... But even then, that is only IF the DACs have sufficient drive current. Otherwise they will be quite limiting. They would each need to be able to drive 1/8th of a chip full of active devices and associated interconnect. So, that may limit the frequencies that we can test at quite a bit. Also, for characterization purposes, we need to be able to do power measurements on the analog input signals, which is probably also going to require external measurement equipment. So, that's another problem. We'd really much prefer true bare analog input pads, if we can get them.