Split keyboards have left and right parts:
The two halves need to be connected. The preferred connection method depends on the number of keys, number of available controller pins, cable flexibility, LEDs, and cost.
connection type | controller pins | wire count | max keys |
---|---|---|---|
just cable | 3 | 6 | 9 |
just cable | 3 | 7 | 12 |
just cable | 4 | 8 | 16 |
just cable | 4 | 9 | 20 |
2 PISO shift registers | 3 | 5 | 16 |
3 PISO shift registers | 3 | 5 | 24 |
I/O expander SPI | 4 | 6 | 64 |
I/O expander I2C | 2 | 4 | 64 |
Fewer wires makes a cable more flexible. A flexibility cable makes it easy to position the keyboard and route the cable. But if there are enough pins on the controller, just using a cable with more wires is simpler and costs less.
I/O Expanders can power LEDs, while PISO shift registers can not.
I2C is a little slow if the I/O expander is scanning more than 4 rows.
connector name | wire count |
---|---|
TRRS | 4 |
6-pin mini-DIN connector (PS/2) | 4 |
USB 2 | 4 |
4P4C Modular connector (RJ9, RJ10, RJ22) handset plug | 4 |
6P4C Modular connector (RJ-14) 2-line phone | 4 |
6P6C Modular connector (RJ12) 3-line phone | 6 |
eSATA | 7 |
8p8c Modular connector (RJ45) Ethernet | 8 |
USB 3.0, 3.1 | 9 |
Only ready-made cables that are widely available are listed. There are hundreds of other connectors listed at http://pinouts.ru/ There are also wireless options if you don’t mind adding complexity and maintaining a battery.
The 8-wire “GearIT Cat 6 Ethernet Flat Patch Cable 7 Feet” is very flexible. It’s available at Walmart (9/19/16) if you want to feel the merchandise before you buy. All the modular connectors are flat.
For prototyping on perfboards, consider a 0.1” header.
keybrd tutorial by Wolfram Volpi is licensed under a Creative Commons Attribution 4.0 International License.
Permissions beyond the scope of this license may be available at https://github.com/wolfv6/keybrd/issues/new.