3 ms·

Split ergonomic keyboards have wrapped all the way around to the simplest possible solution - they have so few keys that each one can simply be connected direct

Split ergonomic keyboards have wrapped all the way around to the simplest possible solution - they have so few keys that each one can simply be connected directly to its own dedicated pin on the microcontroller, no diodes or matrix scanning required. e.g. the Ferris Sweep: https://github.com/davidphilipbarr/Sweep https://github.com/davidphilipbarr/Sweep That has 17 keys per side, which is the most you can do with the 18 GPIOs broken out by the popular Pro Micro modules, but with something like the RP2040 you could scale it up to 29 keys per side if desired.

Karliss 3y ago
No diodes, no matrix all you need is two microprocessors (in addition to your computer) communicating with each other over custom serial protocol. Definitely the simplest solution.
- jsheard 3y ago
  Every modern keyboard uses a general purpose MCU anyway (formerly AVR, now usually ARM) so it's not like they're adding any complexity by using MCUs, and regardless of how the key scanning is implemented you would still want a programmable processor to support all of the layers and macros required to make such a small keyboard practical. Some early iterations of split keyboards did use a parallel bus between the halves instead, which allowed them to have a single matrix spanning both sides which was read by a single MCU, but that went out of style since the cables were unwieldy and MCUs are cheap. Now they all use two MCUs linked over serial, or wireless.
  - kps 3y ago
    Or an MCU and a GPIO expander like a 23017 over I²C.
    - crote 3y ago
      GPIO expanders are surprisingly slow and quite expensive. A two-MCU solution is almost always the better option.
- mananaysiempre 3y ago
  Cost is definitely a part of the definition of simplicity in board design; so is ease of development. So yes, it does feel perverse but just sticking a microcontroller in it is often the simplest solution to a low-speed digital problem. Somebody had to design that microcontroller and it probably has a bunch of errata that basically say a quarter of it doesn’t work, but that’s already done and they are not that much more expensive (if at all) than a 555 timer. It probably isn’t even losing on power consumption. Simplicity is weird.
klysm 3y ago
That’s how I implement my keyboards. Much smaller part count and way easier to code

Karliss 3y ago

No diodes, no matrix all you need is two microprocessors (in addition to your computer) communicating with each other over custom serial protocol. Definitely the simplest solution.

jsheard 3y ago
Every modern keyboard uses a general purpose MCU anyway (formerly AVR, now usually ARM) so it's not like they're adding any complexity by using MCUs, and regardless of how the key scanning is implemented you would still want a programmable processor to support all of the layers and macros required to make such a small keyboard practical. Some early iterations of split keyboards did use a parallel bus between the halves instead, which allowed them to have a single matrix spanning both sides which was read by a single MCU, but that went out of style since the cables were unwieldy and MCUs are cheap. Now they all use two MCUs linked over serial, or wireless.
- kps 3y ago
  Or an MCU and a GPIO expander like a 23017 over I²C.
  - crote 3y ago
    GPIO expanders are surprisingly slow and quite expensive. A two-MCU solution is almost always the better option.
mananaysiempre 3y ago
Cost is definitely a part of the definition of simplicity in board design; so is ease of development. So yes, it does feel perverse but just sticking a microcontroller in it is often the simplest solution to a low-speed digital problem. Somebody had to design that microcontroller and it probably has a bunch of errata that basically say a quarter of it doesn’t work, but that’s already done and they are not that much more expensive (if at all) than a 555 timer. It probably isn’t even losing on power consumption. Simplicity is weird.

klysm 3y ago

That’s how I implement my keyboards. Much smaller part count and way easier to code