Homebrew pi400 (2025 Update)

The keyboard seems like an awkward place for the mobo. It's easier imho to use the monitor as the foundation and fasten the Pi to the back of it. Some Pi cases have keyed mounting holes that hang the case neatly on wood or sheetmetal screws set in a (carefully chosen non-interfering) convenient spot. Cables and keyboards are thus standard, ventilation is decent. The Pi is as safe as the monitor against mechanical mishap or abuse.

Hope this helps,

bob prohaska

That's one of the reasons I never saw the point of the Pi400, with all the wires attached to the keyboard unit, particularly as the keyboard is small and not the highest quality. That and it reminds me of my first Acorn Electron, which I loved but hated at the same time for being slower than the BBC B and no MODE 7.

All of my 'desktop' Pi's and their associated wiring go behind the monitors and TVs out of the way. In the study, I have a single high quality wireless keyboard and mouse which allows me to talk to a Linux Pi 5, a RISC OS Pi 4 and a Linux laptop connected to dual monitors. In the living room I have full sized wireless keyboard and trackpad, and in the bedroom a mini wireless backlit keyboard and trackpad talking to the Pi 5s connected to 4K TVs.

---druck

The keyboard has a Holtek HT45R0072 (one time programmed) microcontroller to convert the matrix to USB. Your options are either to repurpose this microcontroller, at which point you need to match the keyboard matrix of the Pi400 (hard):

I didn't htink of searching for the keyboards, I actually searched for 'homebrew raspberry pi 400.' They are a good start.

Honestly, I'm not necessarily looking for mechanical keyboards. I've used only membrane keyboards my adult life and, well, my wife often naps on my den couch while I'm typing along and I think a clicky clacky keyboard would end that habit. I rather enjoy when she naps in there with me.

I would focus this project mainly on a mass produced full sized keyboard with a decent sized bottom tray that can be hacked to hold the pi400 mobo.

I read the same thing - and it would be a pain in the butt since that microcontroller is, like you said, one time programmed so it's static.

This is exactly the information I was looking for. With good documentation, I surmise I could solder in some wires onto the USB lines and hack in a USB female. If I were to use a wired USB keyboard, I could cut the wire short, rewire the male usb port, and plug it into the female one I hack in. That way, if I want to replace the keyboard with something new, it would require no new soldering.

Or I could make it permanent by cutting the wire short and solder them into the board. I have some reading to do.

I saw the orange pi 800, which I hadn't heard of before. I considered buying it instead but it's way more expensive and the keyboard looks just as junky. And 4gb of ram shut me down.

Thanks for the info.

Daniel

Well, I'm still on the quest for my modded Pi400. I'm currently on one of the keyboards that seemed promising in terms of shell depth (Logitech K120 with silicon membrane). The illusion, I realize, is in the full-sized keys and their travel with the membrane below. I'm sort of addicted to this thing, as it's plugged into my pi400.

Anyway, after work I'll be making a voyage to the next city over from mine and their goodwill. Going to buy up any potential keyboard from the electronics area and see if any will fit a pi400 mobo.

At some point, I will give up on doing a simple shell mod and design an extended lower shell for 3d printing. The big challenge for me is the size limitation on the printer areas. They don't seem large enough to fit an entire length of a full keyboard. I'll have to design a two-piece shell and rely on the screws.

I have three of a particular model of Dell keyboard SK-2885. So far, it's the closest thing I have that's moddable. I made a little video about it on rumble, check it out.

I am typing this on an original IBM Model M. Since I have a disassembled spare sitting next to me, I just checked: a normal Banana Pi Board (same size as an old RPi) fits fine into the space under the keys at the back - so if you de-solder the GPIO header and solder in an angled connector, this might work ;-)

You would need to convert the keyboard to USB, eg. using

My brother has a plethora of model m's. They're fine and all, just out of production and expensive.

I've made strong inroads. A colleague of mine runs a small 3d print business and I've discussed what I want to do.

He showed me that there are tons of pi400 projects already done and plans on thingiverse as we speak. They're all, mostly setup for mechanical keyboards.

So we're going to use a project already created and adapt it for a larger keyboard, then slice it up so it'll fit on his print area.

The nice thing is, I have an existing bottom shell that seriously only needs a small tweaking. We can fix an existing model with the measurements of the keyboard I want to use and adapt it from there.

The keyboard I selected is a HP SK-2885 because the keyboard assembly is conveniently attached to the top shell.

So, I'll keep the progress updated and will post videos as we go.

Wellp, glad I didn't very far on my homebrew pi400 project. Now that they quietly released the Pi500, I'll be focusing on that now.

I still have to watch the youtube reviews of it.

I read Jeff Geerling's recent write-up on it

Jeff's review was the first one I watched, and currently watching the tearapart. From appearances they utilized a better keyboard than the crap on the Pi400. And if this is the case, my homebrew project won't be going anywhere.

I'll be ordering the standalone when someone has them in stock. Right now, I can't find a vendor who has it available.

Presumably, before too long there will be a Pi5x0 where the M.2 socket and associated components are fitted.

Re: Re: Homebrew pi400 By: Daniel to Daniel on Mon Dec 02 2024 17:03:16

Go on any social media site. Nobody would notice, unfortunately. Glad to see someboy still bothers to do it, though.

I was wondering why it was ommitted on initial release, and the only thing that came to mind was, they hadn't finalized its design and wanted this initial version out for xmas.

Jeff did a teardown on his second channel and soldered a m.2 socket hoping it was properly designed. He found the power lines weren't traced in so no power.

He assumed they'll release a pro version with the socket populated and powered.

There also seemed to be an area on the main board with poe considerations, which would be dope. The switches on my network have poe capabilities so that would make my day.

The device isn't in stock anywhere yet, so I will hold off a few months and get it in the spring.

There were some nearby component missing too, maybe the Rev1 board has bugs, and they need a Rev2 (or whatever) but his soldering job looked relatively clumsy (bridged pins etc).

Yeah, it was pretty bad, at least he was honest about it.

I am sure things were missing to keep the circuitry disabled and I'm no engineer.

Why would you put support chips on if you were not going to install an M.2 socket anyway?

I think he called it right in that this is a bare bones model, and more upmarket versions will emerge in due course.

Looking at:

Theo

Ah, I see them now. To the right of the spot on the silver chip are four tiny spots for passives, oriented at compass bearing 135 degrees. I can't tell from the photo or video whether they're populated or not, but those will be the series capacitors.

Theo

^^^^^^^ Making a spelling mistake while discussing spelling is a most frustrating thing. :-)

BTDTGTS (been there, done that, got the scars)