For TT06 we have analog capabilities with a transmission gate based mux. I'd like to be able to characterise the signal path. I've just made a simple loopback module, so a 'round trip' measurement could be made with that. Any ideas for other measurements / test structures?

I assume all analog connections to GPIOs are separately enabled through a transmission gate? And a loopback connects a GPIO pin to another GPIO pin through (presumably) two switches? Seems like a decent way to characterize the switches.

http://www.testedgeinc.com/docs/atb.pdf An ATB would be a cool feature for low frequency signals.

@Luis Henrique Rodovalho: The analog switching connections of the next-generation Caravel are something like that; there are many ways to connect an analog block (including from the user project) into an ADC or to a pin, or get its input from a voltage reference or a DAC. I guess the only real difference is that there isn't a single "test bus" connected to everything; there are multiple buses that can operate in parallel. I will need to write up a thorough description of how a user project can connect into the system for testing, because that's a set of use cases above and beyond the use of the analog blocks for handling analog I/O to connect into a digital core. (So you need to design a great op amp; it's going to be a major component of that system!)

@Daniel Arevalos can you share your findings when designing the analog mux we taped out?

Yes that's the plan atm