keyboard | Code and Life

DIY Bluetooth Keyboard Breakout for $10

You could get an excellent Bluetooth keyboard controller from Adafruit called Bluefruit EZ-Key which allowed super easy creation of projects that sent keyboard presses (for example a gamepad) just by connecting some switches to the pins. However, the EZ-Key cost $20 and is now discontinued. And in any case, Bluetooth-capable devboards are now available from AliExpress for a few dollars, so $20 today feels on the steep side. “Could it be done cheaper?” I wondered…

I have honestly about a dozen cheap wireless devboards lying around, many based on ESP8266 which only have Wi-Fi, but some also with ESP32 which includes Bluetooth. I spent some time trying to configure a Chinese ZS-040 serial Bluetooth module to function as a keyboard, but the AT command set was a very small subset of what the similar HC-05 / HC-06 modules have. After an evening of trying, I decided to give up on that. There are instructions how to flash HC-05 modules with RN-42 firmware to get Bluetooth HID capability, but it will require quite a few steps.

I also took a look at esp32_mouse_keyboard project, but for some reason or another, abandoned that avenue. Don’t recall if there were obstacles or the project was still incomplete a year ago, might also be that the ESP32 only had BT LE which technically didn’t support HID (Human Interface Device). Throw me a comment if you have that working!

Meanwhile, another idea dawned to me:

A Cheap Bluetooth Keyboard Must Contain A Bluetooth Module

Enter the wonders of AliExpress: While you cannot source an easy BT keyboard module from US under $20, you can get a full mini Bluetooth keyboard for $9.50 (at time of writing) including postage! This package ought to contain:

A fully compliant Bluetooth board that pairs with iOS, Android and PC devices
Full functioning keyboard and case
Presumably, a battery and a way to charge it

Sounds a too good deal to be true? Well, let’s find out! The keyboard has a solid metal backplate that is easily screwed open with micro cross head screwdriver. Once inside, it reveals a very professional layout with a flat ribbon cable (or “FCC cable”) coming from the mechanical part into the controller module, And a small (most likely LiPo) battery.

Taking the tape off and turning the board around reveals a bit spacious, but very professional looking PCB with clear markings. There are easily usable on/off switch and connect button on the PCB, a connector for the keyboard switches, and obviously some kind of microcontroller wired to the connector, as well as another smaller chip that is most likely a voltage regulator or charging chip.

I Googled around to find out if the “YC1026” MCU would have a datasheet to help me along the way, but unfortunately I only got Chinese web pages (most likely the manufacturer) without any documentation. Time to dig out my trusty Picotech 2000 scope and do some old-fashioned reverse engineering!
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Topre Realforce 88UB – A Happier Hacking Keyboard

This is my review of the Topre Realforce 88UB mechanical keyboard with evenly weighted 45g switches and UK layout. This is the ISO layout sister model of the Topre Realforce 87U (87UB / 87UW) so everything in this review will apply for that model, except a few layout details regarding the extra keys. Before diving into details, a short background of my previous journey:

Two years ago I got really interested in high quality mechanical keyboards. After all, the keyboard is the instrument I use several hours every day, so if I am spending close to 2000€ on a workstation and display, why should I compromise with a cheap 30€ keyboard, especially since the keyboard will likely last several workstation lifespans?

After heavy research I settled on Happy Hacking Keyboard 2 Professional due to its compact “hacker” layout which seemed great for vim, and Topre key switches, which many consider to have the very best tactile feel. See my review of the HHKB2 keyboard for details.

However, in two years of typing with the HHKB, I never fully learned to use function key bindings for cursor keys and Home/End fluently. Coding with Vim somewhat alleviated the problem, but every time with a command prompt or a shell this nagged me. Also, playing games required a separate keyboard, as most games make use of function keys, and many make use of both WASD and cursor keys. It was time for something else. Something better.

Topre Realforce 88UB – Best of both worlds?

After my experience with HHKB, I had the critical components for my dream keyboard well thought out:

Tenkeyless model with dedicated cursor and function keys. I’ve also used CM Quickfire TK and I can say from experience it is a terrible idea.
ISO layout, so I get the \ and | right next to my right pinky, and an additional key next to z to get < and > in Finnish keyboard layout (it doubles as another \| in US layout)
Topre switches for the ultimate typing comfort. Having used rubber dome, scissor mechanisms and Cherry MX blues, and trying out reds, blacks and browns, there really is no competitor. Buckling spring is just too heavy and noisy for my taste.

The items 1 and 2 are quite easy, but the third one essentially meant that the Topre Realforce line would be the primary candidate to fill all these needs. I’ve used The Keyboard Company before and they have a superb selection of Topre models, so I quickly zoomed in on the black 88-key model with UK layout:

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HHKB Professional 2 Keyboard Review

The keyboard is something that I use daily, and whether I’m writing e-mails or coding, I’ll likely do several hours of typing a day. Last summer when I switched to US layout in coding and started using Vim, I started thinking that maybe I should upgrade my seven year old Logitech keyboard to something hopefully better. And when I get such a project, I did what I always do: Went totally overkill with research and ended up spending a few hundred euros once I had made up my mind on the “most optimal choice” for me. :)

Update: If you’re interested in this review, you might want to check out my continuation with the Topre Realforce 88UB.

Keyboards: 101

My worldview after 2000 was essentially that laptop type flat keyboards are the way of the future, and keyboard choice mainly depends on whether you buy a Logitech or Microsoft one, and do you get the top of the line model or an OEM version for 15 euros. Enter Geekhack and some interesting discussions at Stack exchange, and it quickly became apparent that there is more to it.

First choice one needs to make is the layout of the keyboard. Kinesis makes some weird looking ones that some people swear by, and there are matrix-type layouts, I decided I would continue to risk carpal tunnel syndrome with a “normal” layout for the time being, as I don’t want to optimize my brain for a keyboard type that would only be available at home.
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Arduino PS/2 Keyboard Tester

Once I got my minimal AVR PS/2 keyboard device built, it quickly became apparent that such a device should be able to respond to rudimentary PS/2 commands if I would like to avoid irritating errors in BIOS and O/S side.

After spending a couple of educating evenings with my PicoScope (the only device I had at hand that could capture several seconds of PS/2 traffic at 100 kHz or more to make sure I detect each individual level change) and trying to understand bit-level PS/2 signals (I’ll maybe do a short post on that effort later), I decided it would be too complicated for debugging my own wanna-be PS/2 compliant device. So I decided to implement a simple PS/2 tester sketch with Arduino.

Basic Arduino Setup

There is already a great Arduino/Teensy library called PS2keyboard that had done most of the thinking work for me – the core of the library is an interrupt routine that is called automatically when the Arduino detects falling edge (logic level going from HIGH to LOW) on the clock pin. In Arduino Uno, pin 3 is attached to INT1, and setting up the interrupt is very simple:

#define CLOCK_PIN_INT 1 // Pin 3 attached to INT1 in Uno
// ...
attachInterrupt(CLOCK_PIN_INT, ps2int_read, FALLING);

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Minimal PS/2 Keyboard on ATtiny2313

I recently got myself a mechanical keyboard (to be precise, a Happy Hacking Keyboard Professional 2). One side effect of this switch was, that the new keyboard no longer works with simple passive PS/2 adapter. And the only type of input my current motherboard can be configured to power up on is spacebar from a PS/2 keyboard.

Well, I had read from somewhere that PS/2 protocol is not too complex, so I decided to find out if I could make a simple gadget that would send spacebar keypress over PS/2 when a switch was toggled. That turned out to be quite easy (with some limitations, read the end of this post to find out more).

PS/2 basics

The Wikipedia page for PS/2 connector already looked promising – there are GND and VCC pins straight available, and only two additional (open collector type) lines are needed for data and clock lines. Communication is bi-directional with the keyboard providing clock signal and sending end toggles data line while the receiving end listens.
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USB HID keyboard with V-USB

There still seems to be a lot of traffic to my V-USB tutorials, so I thought I’d write a short follow-up post on USB keyboards. I already did a USB HID mouse post earlier, so you might want to check that out to understand a bit about HID descriptors and associated V-USB settings (in short, human interface devices send a binary descriptor to PC telling what kind of “reports” they send to the host on user activities).

As a basic setup, you’ll need a working V-USB circuit with one switch and one LED attached. Here, I’m using ATtiny2313 with the LED wired to PB0 and switch to PB1. The ATtiny is using 20 MHz crystal, so if you’re following my USB tutorial series and have that circuit at hand, remember to change that frequency in usbconfig.c before trying this out. Note the cool breadboard header I have, there will be more posts about that one to follow soon!
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