Author Topic: QMK: RGB Matrix Wiring  (Read 582 times)

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Offline Zuve

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  • Posts: 2
QMK: RGB Matrix Wiring
« on: Tue, 01 October 2019, 22:52:03 »
I'm looking to create a custom PCB with RGB backlight. I have two questions:

1. What are the pros/cons of using simple WS2812b LED's wired together vs using a dedicated matrix driver such as the IS31FL3737?

2. Currently trying to design around the IS31FL3737 for my LED matrix. In the QMK docs for RGB Matrix it states the following regarding the DRIVER_ADDR_1 define:
Code: [Select]
// This is a 7-bit address, that gets left-shifted and bit 0
// set to 0 for write, 1 for read (as per I2C protocol)
// The address will vary depending on your wiring:
// 0b1110100 AD <-> GND
// 0b1110111 AD <-> VCC
// 0b1110101 AD <-> SCL
// 0b1110110 AD <-> SDA
I'd appreciate it if someone provide me with further explanation regarding what these comments mean. I understand that GND, VCC, SCL, and SDA are relevant pins for I2C communication, but what is AD in this context, and is this referring to the pins on the AVR or the LED matrix driver? If anyone could point me to an actual PCB schematic(So few open source designs out there) demonstrating the wiring that would also be helpful. Thanks!

Offline piit79

  • Posts: 144
Re: QMK: RGB Matrix Wiring
« Reply #1 on: Wed, 02 October 2019, 01:00:21 »
The main difference is that WS2812b will actually give you RGB, whereas the matrix driver is for single-coloured LEDs.

Regarding the AD pin - it basically sets one of 4 possible chip addresses, depending on where it's connected. Try Googling the chip name with site:issi.com - their PDF datasheet might be easier to understand.

Offline Blitzschnitzel

  • Posts: 67
Re: QMK: RGB Matrix Wiring
« Reply #2 on: Tue, 08 October 2019, 04:43:25 »
The main difference is that WS2812b will actually give you RGB, whereas the matrix driver is for single-coloured LEDs.

You can use a matrix driver for RGB LEDs. You just hook a 4 pin RGB LED to the matrix as if it were three separate LEDs. Your maximum number of LEDs per chip is then off course 1/3rd of what it would be with a single colour.

Offline piit79

  • Posts: 144
Re: QMK: RGB Matrix Wiring
« Reply #3 on: Tue, 08 October 2019, 05:52:37 »
You can use a matrix driver for RGB LEDs. You just hook a 4 pin RGB LED to the matrix as if it were three separate LEDs. Your maximum number of LEDs per chip is then off course 1/3rd of what it would be with a single colour.

OK, that's true. But you will have a whole lot more traces to worry about. The RGB LEDs with integrated driver are a bit more expensive but probably more convenient.