- Correct, you can set the color and intensity for each half independently, all keys show the same color and same intensity per key.
- Second, you could add individual LEDs but it's not trivial, I want to just quickly review why I chose to use a single LED per half and fibers rather than individual LEDs
Single and dual color LEDs come in 2 pin through hole mount packages, typically 3,5,10mm width, for a Cherry switch you really want the 3mm without a collar. In the case of dual color LEDs you have to switch the anode and the cathode to switch colors (so you still need to wires to controller).
RGB LEDs always have at least 4 pins, this poses a problem since the Cherry switch only has mounting holes for 2 pins, it might be possible to hack this using a custom top since the bottom actually has 4 holes in it. The second problem is that nobody makes RGB LED's in 3mm packages, the smallest I have seen is 5mm.
Let's say we found an RGB LED and found a way to mount it in a Cherry switch, we now have to worry about power, a single USB connection can supply 500mA @ 5v, some of this is taken by the teensy and the IO expander. Since you have 80 LEDs to deal with you would need to find 5mA LEDs, assuming you would be using resistors to limit the current, note that this is 5mA per color and assumes that you would only ever power one color of the LED at a time. For a full low loss controller circuit without resistors you would be talking about a lot of money and chips.
Now to control these, simplest would be a single jumper per color per switch (120 jumpers per half), not very practical thought. Probably would want some sort of microcontroller or IO expander that would allow dimming/mixing of colors, but you would need something with at least 120 PWM capable pins.
Then we need to worry about wiring, assuming ground is available at the switch we still need to route 120 wires per half back to the controller and add 120 resistors to the PCB.
Having mentioned all of that you can still add the diodes, I use the standard mounting holes to route the optical fibers so you could put a standard diode in there but it would not be connected to anything.
Been working on the RGB backlight edition, figured I'd give an update.
So the backlight will give every key the same color? We may change the colors of the two halves independently, but can not change the backlight of individual keys?
In your PCB, I see LED connection pads for every key switch. Does this mean that we can add LEDs (single color) for every key, and modify the firmware so that one may control the backlight of each and every key? For example, light up a LED when a key is pressed?
