Zorchpad keyboard update

The Zorchpad needs a custom keyboard. Its power budget is only 1mW, and there’s just nothing available in that range. So, I need to make a custom keyboard. I started reading up on how to make your own–especially the electronics.

I don’t know how to make a PCB:

PCB from HacKeyboard

Or how to attach headers to the inside of an existing keyboard, which looks like this–:

Mapping the Innards of a Keyboard : 7 Steps (with Pictures) - Instructables

But I found a project called GOLEM with an excellent guide to making your own keyboard. Here is their wiring:

GOLEM Macropad

I can do that! They got me out of a major rut.

Their advice walks you through how to do a small keyboard in a cardboard plate. I did a few keys, gauged the effort, and decided to use my 3D printer. Cutting out 50-60 keys precisely by hand doesn’t sound easy. Worse, if you mess up, you have to start over. In plastic, I can’t mess up halfway, and the spacers to support the keyboard can be part of the print.

Above, I’m designing a “sampler” keyboard in CAD (OpenSCAD). I want to iron out problems in my process before I try a full-size keyboard. Below, Prusa-Slic3r is slicing the finished model for my 3D printer to print.

Here’s the finished sampler keyboard:

Currently I’m waiting on keycaps and switches ordered from China, and then I’ll put together my finished keyboard. But I have been making some progress in the meantime. Here’s the layout I’m going to try.

And I’ve started streaming some development of a case and keyboard on Twitch (Tue/Thu 12pm noon, EDT). Feel free to join! Anyone can watch, but you need an account to chat.

Zorchpad Update: Cardboard mockup, mk1

I’ve gotten to the point in Zorchpad development where I’d like to see how the whole thing fits together and if there will be any insurmountable problems. We’re still trying to figure out some things like–will it have one screen or two? What form factor will it be? Will the keyboard fold in half? So I put together a cardboard model.

This model has:

  • A power switch. I’m assuming the very first prototype will run on battery, not solar like the final one.
  • Two memory-in-pixel screens (total power usage: 0.001 W)
  • One e-ink display (total power usage: variable/unknown)
  • An apollo3 artemis board, which includes RAM, CPU, microphone, and BTLE (not pictured, total power usage about 0.0005 W)
  • One flash chip (not pictured, power usage variable)
  • A battery slot. I’m using AAA for my convenience (Holds: 3000 joules = ~20 days power)
  • An audio jack for headphones
  • A microSD slot
  • A custom keyboard (total power usage: variable/unknown)
    The keyboard is closely modeled off a standard one, for now.

Immediately, a few problems pop out:

  • It’s fairly long. This will stick out of my pocket. This is with very closely spaced keys on a somewhat reduced keyboard.
  • There’s not really a great place to put solar panels. It’s has almost zero free space, plus there’s going to be a lot of wiring. Are we going to drill holes through the solar panel to let wires pass through? Also, I really haven’t been able to figure out how many cm2 of solar we need.
  • It’s hard to get the screen to stay propped up on my cardboard model. I’d like a solution that doesn’t use hinges, since those tend to loosen over time.

My next step will probably be to make a custom working keyboard. Then, I’ll make an entire working zorchpad. Both will be either cardboard or 3d-printed (whichever is easier).

Zorchpad Update: Keyboard

Another update on the zorchpad. We now have a working 16-button keyboard (sadly no QWERTY yet). Here you can see a simple typing program that shows what you type on screen.

As mentioned in a previous post, the reason we’re using a custom keyboard is to stay to low power usage–much lower than a standard keyboard.

So far we have:

DIY keyboards (and how keyboards work)

I’ve been pondering simple input methods for microcontrollers. One obvious idea is, a keyboard! But for some reason, my USB keyboards use a staggering amount of power compared to my microcontrollers–1W of power for my mechanical keyboards, maybe 0.1W for the regular ones.

Let’s look inside a commercial keyboard, and see if we can hook up to it:

a photograph of the interior of a commercial keyboard. there is a PCB, with two layers of flexible conductor on top, all clamped down

Yikes. What’s going on? Well, let’s make our own little keyboard, and explore what’s going on. We’ll build it in three layers, or “index cards”:

The bottom layer has 6 vertical stripes. The top layer has 3 horizontal stripes. Each place they cross will be a “key” you can press.

In between them, we add a spacer layer (punched holes) so they keys are “up” by default, and you have to press them to make them connect.

This picture might help explain how they will go together:

Now we assemble:

The final keyboard has 6 x 3 = 18 “keys”. We write the hex digits plus a couple extra keys with marker.

If I attach alligator clips to the second horizontal screw terminal, and fourth vertical screw terminals, and wire a battery and buzzer with the terminals, I get a connection beep only when I press the key “A”:

Two terminals with alligator clips attached to row and column terminals, and a screwdriver pointing at the "A" key addressed.

In a real computer, we obviously can’t just move alligator clips around. Instead, we attach wires to all 9 posts–three outputs wires for the horizontal lines, and six inputs for the vertical lines. We output a signal on the first horizontal line, and see if we can read it from any of the six vertical lines inputs. Then we output a signal on the second horizontal line, and see if we can read it, and so on for the third. Assuming only one key is pressed (or none), we can identify the key. This “scanning” process could be done thousands of times a second, rapidly enough that it can’t miss our slowpoke human fingers.

Schematic of a keyboard, provided by Kragen
Click to view interactive schematic (credit: Kragen)

And this is how most keyboards work. There are some special keys–Shift, Ctrl, Alt, etc might be on their very own line, since we want to detect key combos. And better keyboards can detect multiple keys being pressed at once (N-key rollover), which I think they do by having a completely separate wire to each key which multiple people tell me they do with a diode next to each key.

For the above project, I used:

  • Three index cards
  • A hole punch
  • Scissors
  • A ruler
  • A pen (NOT a pencil, since graphite is conductive)
  • 9 screws, 9 nuts, and 18 washes. I selected #6 American Wire Gauge, which is about 4mm thickness
  • Copper tape

Did this work perfectly? Definitely not.

  • On some keyboards I’ve made, you have to press quite hard.
  • My multimeter takes a while to register a press. I think a microcontroller would be better.
  • You have to attach the terminals carefully. I think what’s going on is that you can actually put the screw exactly through the center of the washer which is actually making contact with the strips, so that only the washer is attached, and the screw doesn’t rub against the washer.
  • It’s of course fairly easy to mis-align anything. This is pretty easy to fix with care. I used the “spacer” grid to draw the centerpoint of the printed letters.
  • The screw heads are a bit thick, so it’s hard to press the keys in the column/row next to the screws. A piece of backing cardboard might fix this.

This was my third attempt. Here’s the second, using aluminium foil. It worked at least as well, maybe better, but it was harder to make. I just taped the foil down, taking care not to cover the contact points. I am told the aluminium will gradually oxidize, making it non-conductive.

And here’s one using graphite from drawing hard with a #2 pencil.. Graphite, it turns out, works terribly, and I couldn’t read a signal halfway down the index card. Despite what people have told me, I’m not yet convinced you can make a conductive wire out of it.

Introducing the Zorchpad (+ display demo)

A friend of mine, Kragen Javier Sitaker has been designing something he calls the zorzpad (see link below). I can never remember the name, so as a joke my version became the “zorch pad”. We live on opposite sides of the globe, but we’ve picked up the same or similar hardware, and have been having fun developing the hardware and software together.

The basic idea of the Zorchpad is to have one computer, indefinitely. It should keep working until you die. That means no battery that runs out, and no parts that go bad (and of course, no requirements to “phone home” for the latest update via wifi!). This is not your standard computer, and we’ve been trying a lot of experimental things. One of the main requirements is that everything be very low-power. He picked out the excellent apollo3 processor, which theoretically runs at around 1mW. In general, the zorchpad is made of closed-source hardware.

Since I’ve realized this will be a long project, I’m going to post it piece-by-piece as I make progress. Below is a demo of the display.

The graphics demo shows, in order:

  • a title screen
  • a flashing screen (to show graphics-mode framerate)
  • a demo of font rendering. we’re using the fixed-width font tamsyn.
  • a munching squares animation
  • a demo of how fast “text-mode” updates would be

We’re using a memory-in-pixel LCD. The only manufacturer is Sharp LCD. You have have seen these before in things like the Pebble watch–they’ve very low-power except when you’re updating. This particular screen is quite tiny–240x400px display (which is fine with me), but only 1.39×2.31 inches (35x59mm). The only bigger screen available in this technology is 67x89mm, a bit lower resolution, and out of stock. As soon as it’s in stock I plan to switch to it.

According to the datasheet, the screen consumes 0.05-0.25mW without an update, and perhaps 0.175-0.35mW updating once per second. We haven’t yet measured the real power consumption for any of the components.

The most obvious alternative is e-ink. E-ink has a muuuch slower refresh rate (maybe 1Hz if you hack it), and uses no power when not updating. Unfortunately it uses orders of magnitude more power for an update. Also, you can get much larger e-ink screens. The final zorchpad might have one, both or something else entirely! We’re in an experimentation phase.

Datasheets, a bill of materials, and all source code can be found in my zorchpad repo. Also check out Kragen’s zorzpad repo.