opensteno_qmk/docs/ws2812_driver.md

WS2812 Driver

This driver powers the RGB Lighting and RGB Matrix features.

Currently QMK supports the following addressable LEDs (however, the white LED in RGBW variants is not supported):

WS2811, WS2812, WS2812B, WS2812C, etc.
SK6812, SK6812MINI, SK6805

These LEDs are called "addressable" because instead of using a wire per color, each LED contains a small microchip that understands a special protocol sent over a single wire. The chip passes on the remaining data to the next LED, allowing them to be chained together. In this way, you can easily control the color of the individual LEDs.

Supported Driver Types

	AVR	ARM
bit bang	✔️	✔️
I2C	✔️
SPI		✔️
PWM		✔️

Driver configuration

All drivers

Different versions of the addressable LEDs have differing requirements for the T_RST period between frames. The default setting is 280 µs, which should work for most cases, but this can be overridden in your config.h. e.g.:

#define WS2812_TRST_US 80

Bitbang

Default driver, the absence of configuration assumes this driver. To configure it, add this to your rules.mk:

WS2812_DRIVER = bitbang

!> This driver is not hardware accelerated and may not be performant on heavily loaded systems.

I2C

Targeting boards where WS2812 support is offloaded to a 2nd MCU. Currently the driver is limited to AVR given the known consumers are ps2avrGB/BMC. To configure it, add this to your rules.mk:

WS2812_DRIVER = i2c

Configure the hardware via your config.h:

#define WS2812_ADDRESS 0xb0 // default: 0xb0
#define WS2812_TIMEOUT 100 // default: 100

SPI

Targeting STM32 boards where WS2812 support is offloaded to an SPI hardware device. The advantage is that the use of DMA offloads processing of the WS2812 protocol from the MCU. RGB_DI_PIN for this driver is the configured SPI MOSI pin. Due to the nature of repurposing SPI to drive the LEDs, the other SPI pins, MISO and SCK, must remain unused. To configure it, add this to your rules.mk:

WS2812_DRIVER = spi

Configure the hardware via your config.h:

#define WS2812_SPI SPID1 // default: SPID1
#define WS2812_SPI_MOSI_PAL_MODE 5 // Pin "alternate function", see the respective datasheet for the appropriate values for your MCU. default: 5

You must also turn on the SPI feature in your halconf.h and mcuconf.h

Testing Notes

While not an exhaustive list, the following table provides the scenarios that have been partially validated:

	SPI1	SPI2	SPI3
f072	?	B15 ✔️	N/A
f103	A7 ✔️	B15 ✔️	N/A
f303	A7 ✔️ B5 ✔️	B15 ✔️	B5 ✔️

Other supported ChibiOS boards and/or pins may function, it will be highly chip and configuration dependent.

PWM

Targeting STM32 boards where WS2812 support is offloaded to an PWM timer and DMA stream. The advantage is that the use of DMA offloads processing of the WS2812 protocol from the MCU. To configure it, add this to your rules.mk:

WS2812_DRIVER = pwm

Configure the hardware via your config.h:

#define WS2812_PWM_DRIVER PWMD2  // default: PWMD2
#define WS2812_PWM_CHANNEL 2  // default: 2
#define WS2812_PWM_PAL_MODE 2  // Pin "alternate function", see the respective datasheet for the appropriate values for your MCU. default: 2
#define WS2812_DMA_STREAM STM32_DMA1_STREAM2  // DMA Stream for TIMx_UP, see the respective reference manual for the appropriate values for your MCU.
#define WS2812_DMA_CHANNEL 2  // DMA Channel for TIMx_UP, see the respective reference manual for the appropriate values for your MCU.

You must also turn on the PWM feature in your halconf.h and mcuconf.h

Testing Notes

While not an exhaustive list, the following table provides the scenarios that have been partially validated:

	Status
f072	?
f103	✔️
f303	✔️
f401/f411	✔️

Other supported ChibiOS boards and/or pins may function, it will be highly chip and configuration dependent.

Push Pull and Open Drain Configuration

The default configuration is a push pull on the defined pin. This can be configured for bitbang, PWM and SPI.

Note: This only applies to STM32 boards.

To configure the RGB_DI_PIN to open drain configuration add this to your config.h file:

 #define WS2812_EXTERNAL_PULLUP