Re: RP400 40-pin connector

"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message news:d21ibjdvt6odqium3ado62ob1e7sa6n9hc@4ax.com...

I want to use an Raspberry Pi 400 (the keyboard thing) as the
dev/debug system for an RP2040 based product.
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https://www.amazon.com/Raspberry-Computer-Keyboard-Layout-Kabel/dp/B08QCQVWH2
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It has a 40-pin connector on the back. Various sources say that pins 1

This connector?
https://www.pi4j.com/1.3/images/pi4j-rpi-400-pinout.png

3 and 5 are either GPIO ports 8 9 and 7 or maybe 2 3 and 4.
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Sometimes the pins are labeled WPI and BCM. Wot's that?
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https://www.amazon.com/Coolwell-Waveshare-Raspberry-Adapter-Expansion/dp/B08RZCR7S8

If that's just a connector then continuity check it to the above drawing of the connector on the Pi.

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I can fix most mistakes there in software, just by reassigning port
names. But two pins are critical, the SWDIO and SWCLK debug lines out
to a Pi Pico or to the 2040 chip.
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I suspect that on the Pi 400 pin 18 is GPIO5 = SWDIO and pin 22 is
GPIO6 = SWCLK.
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Is that right? Does that actually work?
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I also note that some people also connect the UART tx/rx between the
Pi400 and a Pico for debugging. Should I do that too? Does it help
software development?
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Thanks!