Subj : Re: RP400 40-pin connector
To   : All
From : Theo
Date : Thu Aug 15 2024 17:46:40

XPost: sci.electronics.design

In comp.sys.raspberry-pi john larkin <jlarkin_highland_tech> wrote:
> Yes, but the port pin nunbering is different from the Pi 4 and 5, so I
> was concerned about which pins to connect to a Pico (or a 2040 chip)
> for program loading and debugging.
>
> This apparently works
>
> https://www.dropbox.com/scl/fi/sd8mkqz3rw55fcevjouvi/OKdo_Pi400_debug_Pico.jpg?rlkey=kb5xjo75n5e5k3ncy4qs2caur&raw=1
>
> and one can actually count the pins on the connectors.
>
> One of my guys is hacking some connections and verifying. We're laying
> out some PCBs for debugging and production test, and we need to get
> the pins right.

Ah, that's SWD *output*.  None of the Pis have specific hardware to act as
an SWD debugger, so it's just bitbanged GPIOs.  For that it's just down to
whatever pins your software has decided to use.  You can presumably
reconfigure it to use any GPIO pins.

(5 and Pico have dedicated SWD input connectors, but that's to allow *them*
to be debugged)

Theo

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