According to the FAQ I should be able to use a Raspberry Pi 400. Is the idea that I just plug the HAT straight into the back, or do I need a ribbon cable?
If I need a cable, would I be able to just plug an IDE cable (female-to-female) into the top male header of the HAT, or will the pins be flipped? Or should I play it safe and get a female-to-male GPIO extension ribbon cable?
Hi @gendor!
There’s probably a few ways you could do it, but I would think a ribbon cable works best (like the one you linked). Use the Pioreactor’s faceplates + standoffs to just as you would with a non-400 Raspberry Pi, but put the male end of the cable where the RPi would be. Does that make sense?
Yep, that’s what I thought I should do. I was kinda hoping that I could get away with using an old IDE cable (female-to-female) instead and plugging it into the top male header of the HAT - would that work?
Oh, yea, I never thought about that possibility. That should work! Let me know how it goes!
@gendor actually if using the female-to-female, you should confirm that the pins won’t be flipped - this could damage the RPi.
@CamDavidsonPilon I finally got it working with the RPi 400. I decided to go withe female-to-male ribbon cable I linked above to play it safe. It turns out that the connector is quite wide, so the standoffs on the one side won’t fit.
I put two nuts on the other side (to even things out) before screwing the standoffs on, and put screws into the HAT PCB to be able to add the upper standoffs.
It was a very long three minutes waiting for the blue LED to blink, but turns out I got things the right way round and everything worked as expected! 
That looks sick! Happy to hear it works, too!
I put two nuts on the other side (to even things out) before screwing the standoffs on, and put screws into the HAT PCB to be able to add the upper standoffs.
Can you confirm this is what you changed?
Yes, exactly! So no extra screws needed - I just moved the 10mm screws from the bottom plate to underneath the HAT PCB. And I made sure to run the ribbon cable underneath so that its pin 1 (far side in the photo) will line up with that of the HAT PCB.
I’m guessing the keyboard is not doing too much, unfortunately? The RPi image I ship is “headless”, meaning there’s no display software pre-installed. Are you interested in setting up a display to the 400 as well? I’ve never tried using a display + Pioreactor on an RPi, as I figured it might tax the RPi too much during Pioreactor’s operations. But it might work! Let me know if you’re interested in trying - it may be a frustrating experience though 
Yeah, I noticed that the display turned off after the initial configuration. I imagine that the RPi 4 on board the 400 should be fast enough to handle the display and Pioreactor, but it’s not a must-have for me right now. I just wanted to get it working with a Pi I already have, as they’re still a bit of a challenge to buy at the moment.
What could be fun though is using the keyboard to interact with the PiOLED display you mentioned in New Pioreactor plugin: pioled_display_plugin !
