Boards using the IS31FL3731 LED driver


12 Sep 2019, 19:26

Hi, I’m new here.
Reddit seems to be the worst place to ask technical questions and electronics forums aren’t up to date with QMK and keyboard design. So here I am.^^
I want to use the IS31FL3731 LED driver in my next board project. Now I would like to ask if someone knows an opensource QMK board that uses the IC on GitHub? I would like to take a look at the schematics and how it is hooked up there. QMK doesn’t make use of the hardware shutdown or the interrupt output from the chip. Right?


12 Sep 2019, 20:08

Welcome! Good questions...

I would try to find keyboard schematics for QMK by first looking for the firmware.

In the official repo, the only Open Hardware PCB I find for the IS31FL3731 LED driver is the Input.Club Infinity 60. There are more keyboards but those seem to be proprietary hardware designs.
The only keyboards supported by QMK's official repo that use "led_matrix.h" seem to be Massdrop CTRL and ALT. However, they use the IS31FL3733. I think Massdrop CTRL is just a clone of Input.Club K-Type whose PCB is also Open Hardware.
You would have to look yourself elsewhere for forks of QMK.

The other backlit keyboards for QMK that I have seen so far have just used a single PWM pin controlling a MOSFET driving all LEDs at once, which I don't think is a good idea.


04 Oct 2019, 22:56

Very late reply but in case someone else is having the same question:
I went through all keyboards in the QMK github which use the IS31FL3731 and none of them are open hardware. Plank has a rev0 schematic online but that design can't possibly work.
I seem like QMK does indeed not make use of the hardware shutdown or the interrupt pin. So, just pull up the SDB pin. I'll have it tested soon.

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