JTAG Support on Bus Pirate v5

Hi phdussud!

Thanks for stopping buy. Dirty-jtag-pico is a great project. I have looked at your project, and I also think dreg may have looked at it. It is on my list to port/demo as soon as SPI binary mode is up and running.

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Any that does JTAG pinout sniffing, pretty please.

do you mean like what jtagulator does?

Juding by its marketing material, yes. I am not familiar with it otherwise. My initial use case is to identify interfaces I could potentially use to program flash on a router before meddling with it’s u-boot.

jtagulator is on the list. Though, due to low pin count, I’m not sure how fun it will be to use.

jtagulator is not so great when there are many pins to test, it is really good for low pin count.
The PIO system of buspirate might even give it an edge

So I can hook it up to what I think is EJTAG and let bus pirate work out whether there’s anything out there?

we still need to implement it, in theory it is possible

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JTAGulator functionality is very useful for beginners who aren’t sure what they are looking for.

One nice thing about the latest version of the JTAGulator software is that it will look for all types of pins in one scan (JTAG, SWD, UART, GPIO).

The product is no longer being made. It’s open source so people can make their own, but some parts are hard to get.

The real problem it that it takes forever to scan. With 24 pins there are a lot of combinations.

There is a version of JTAGulator that works on a Raspberry, although it does not have the 24 I/O pings. It’s called JTAGenum

It only has 6-8 pins for scanning depending on the board.

The issue is that when you add more pins (i.e. going from 8 to 24) is that the time increases geometrically. I’ve run it for hours and hours and it never finished.

I believe the Glasgow board has a JTAGulator function.

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Here’s another JTAG scanner written in GO for the RPi - GitHub - gremwell/go-jtagenum: JTAG enumeration tool written in Go. A port of https://github.com/cyphunk/JTAGenum enhanced with https://github.com/grandideastudio/jtagulator improved implementation.

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I would like to take another vote if I may. I think I figured out the pin order. :smiley: The jtag feature @phdussud mentioned is on the top of my wishlist now.

At the moment I can detect 4-5 taps with openocd but it complains about some missing isa register or what not and it wont halt properly let alone run any program. So, tbh, I am not sure if it’s me, the probe (bus blaster 3) or openocd where the problem lies.

All in all, I am not really sure how jtag probes differ from each other. Am I out of luck with open source solutions and should I try to hunt down what mediatek mt7621 dev boards play along nicely with.

The OpenOCD docs on Debug Adapter Hardware might be a good start.