Re: Raspberry Debug Probe query

On Sat, 2024-06-22 at 17:28 +0100, Theo wrote:

Single Stage to Orbit <alex.buell@munted.eu> wrote:

Does anyone knows how to use the Raspberry Debug Probe with a
Raspberry Pi 3B? I've googled but the articles I've found only
explains how to use it with Raspberry Picos. I have a tricky issue
to diagnose and it needs hardware level debugging to see what's
going wrong with it.

 
What do you want to debug?  The regular Pis have JTAG to which you
can hook up a debug probe and run something like OpenOCD+gdb on
another machine (you can likely do that from another Pi using GPIO,
or a USB JTAG widget).  But you're debugging the whole OS including
all the daemons and whatnot that are running on it.  Unless your
issue is with the kernel itself (eg a boot failure) or with some code
running bare-metal, I don't think JTAG is going to help much.
 
The Pico's Debug Probe provides SWD, which is for microcontrollers
but not for application-cores on the big Pis.  It provides 2 signal
wires where JTAG needs 4, so I don't think you could repurpose it for
JTAG even if you wanted to.

So that's the difference, thanks for the info, much appreciated. To sum
up SWD on the Raspberry Pi probe only good enough for rp2040s and
others with SWD.

What do you suggest I use on raspberrypi instead? It is indeed the boot
process I need to debug. It is working OK in Qemu 9.x but does not boot
on real rpi hardware, either rpi3 and rpi4.
--
Tactical Nuclear Kittens