JTAG

[0Grit]

Please expose JTAG on a standard pin header in addition to the standard cortex debug 10 pin header.

[igrr]

Hi @0Grit,
I think we were considering to use the built-in USB-SERIAL-JTAG peripheral of ESP32-C3, as that would provide both JTAG and serial console while occupying only two pins of the chip, and requiring only one USB cable. This built-in adapter is now supported in probe-rs: probe-rs/probe-rs#863.

Do you envision some situations where you would prefer to use an external probe instead of the one built into the chip?

[pedrominatel]

@0Grit I see no problems with exposing the JTAG pins using the 10-pins 1.27mm.

Is there any special requirement for the connector? Usually, the 10-pin JTAG connector is more common these days.

[0Grit]

Often its called "cortex debug connector". It obviously needs a more generic name than that in this case.

Will there be any other connectors on this board?
I still want to be able to fixture this thing so I can do automated testing. I want to be able to breakout the buses etc. just by popping this board into a custom baseboard.

I'm thinking something like using the standard "feather" pinout but extend it a couple pins in order to support JTAG. And definitely bring that awesome usb/jtag perioheral over too.

I am already in the process of building out a cart specifically to do on target testing of Golioth's DSDK for other boards.

If you would like to do a call to discuss this stuff please do. I have a good bit of experience architecting boards like this. Happy to help any way I can.

[pedrominatel]

@0Grit the form factor of this dev board is still open. The idea is to use something already in the market (Adafruit Feather i.e) and not to create something new.
We can extend all pins to the 2,54mm headers, including the JTAG, and also add the 10pin JTAG connector.

We can make this call if you want and you'll be more than welcome to help on this project!

[0Grit]

@pedrominatel As a professional who has both designed PCB's and specializes in firmware + IoT; I purposely avoid dev boards that use the feather footprint.

The feather footprint has no standard pins for debug.
With no standard way to debug a feather board this also means there is no way to do automated tests generically across feather boards.

So what I am proposing is to use this as an opportunity to extend the feather footprint 'standard' in a way that is backwards compatible, that better accommodates professionals and possibly production use cases as well.

[pedrominatel]

This is a good idea. Let's think about this extended Feather footprint. If you have any suggestions for the pin layout, please share them with us.