Cherry MX LED lights

[spuder]

Allow modders to use cherry mx switches with LEDs

• [x] Update library to use cherry mx pinout with led holes. example done: https://github.com/UltimateHackingKeyboard/ugl-kicad-libs/pull/2
• [ ] Choose a led driver that handles PWM
• [ ] Determine if sufficient pins available on the AtMega for led driver
• [ ] Design charlieplexing matrix

Optional features

• [ ] Software defined brightness, [like code keyboard https://codekeyboards.com/])
• [ ] Individually toggle buttons (caps lock, num lock)

Related https://github.com/UltimateHackingKeyboard/electronics/issues/13

[mondalaci]

It'd be useful to take a look at some open source keyboard designs that have backlighting. I'd rather go for a simple implementation that supports a single PWM channel for all the LEDs. So I mean no per-LED backlighting.

[spuder]

Some possible led drivers

74HC595 Shift Register

• only needs 3 pins (SPI)
• can daisy chain
• Have to do charlie plexing in software

MAX7219 Led Driver

• Handles control and refreshing. Greatly simplifies code
• Kind of expensive.

I'm leaning towards the first option because it is cheaper.

The teensy has an spi library https://www.pjrc.com/teensy/td_libs_SPI.html

[mondalaci]

I'm aware of these options. Unfortunately, the 74HC595 only allows for a single LED per pin and the MAX7219 is fabulously expensive.

I've been suggested the TPS61193 lately which may work for us. We could string about a dozen of LEDs per OUTx pin.

I personally don't feel confident in my abilities to choose the best part for this purpose and will surely talk to an electronics engineer before making a choice. But suggestions are always welcome!

[spuder]

Looking at the ergodox infinity, they are using the IS31FL3731C

[mondalaci]

Yes, I know, but nobody has it on stock which is not very promising.

[mondalaci]

Apparently, this IC is available without the closing C in its part name.

[mondalaci]

Done. We went with the IS31FL3731-SALS2.