(Fomu) examples/soc/: "nmigen.build.res.ResourceError: Resource uart#0 does not exist"

[greatscottgadgets]

(Fomu) examples/soc/: "nmigen.build.res.ResourceError: Resource uart#0 does not exist"

[ktemkin]

Oh! I think when we spoke earlier I didn't get that you were using some of the SoC examples. Those don't currently work on fomu; because the SoC example chosen implements a hardware UART, rather than a virtual one.

If you're trying to use this with a virtual serial device, that'd require implementing a simple SoC peripheral that, in turn, interfaces with LUNA's simple ACM virtual-serial, as here:

https://github.com/greatscottgadgets/luna/blob/master/examples/usb/acm_serial.py

[ktemkin]

A (more complex) example of a peripheral is provided here:

https://github.com/greatscottgadgets/luna/blob/master/luna/gateware/usb/usb2/interfaces/eptri.py

You'd theoretically need to wrap LUNA's USBSerialDevice with a Peripheral, and then add e.g. a CSR (register) you can use to send data. I think that'd be a super interesting example -- feel free to open a feature request. :)

[ktemkin]

I'm closing this since it's not technically a bug; I'd love to have this referenced in a new feature request, though, if you're willing to write one. :)

[mithro]

@ktemkin - I think @tcal-x wants to use the LUNA core to handle the USB serial side and LiteX to provide the CSR peripherals. I /think/ the best way is to set up LUNA to provide a byte-FIFO like interface similar to what the FTDI ICs provide, then connect that to the LiteX byte UART peripheral which would normally talk to something like the FTDI IC? Does that make sense?

[mithro]

My poor attempt at doing a diagram is shown at https://docs.google.com/drawings/d/1JMEMoRK5CP7TDy4U9-tuYUZqEjzRmwVNJWENpQxgR9g/edit

[tcal-x]

Thanks @ktemkin , yes we chatted a bit on discord (1bitsquared). So yes, things are working as expected, not a bug. I think I did have success with the acm_serial.py design. Also, loopback.py didn't meet timing with the default pnr seed, but did meet timing with --seed 198.

I do have a working solution on Fomu with valentyusb and I think tinyusb, hooking into the uart / putc / printf stack (I hope that makes sense, I'm still figuring things out). But I'd love to get to the same point with Luna too. I'm not sure which if any pieces are missing.