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qmk_firmware/docs/ws2812_driver.md

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WS2812 Driver :id=ws2812-driver

This driver provides support for WorldSemi addressable RGB(W) LEDs, and compatible equivalents:

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

These LEDs are often called "addressable" because instead of using a wire per color (and per LED), each LED contains a small microchip that understands a special protocol sent over a single wire. The LEDs can be chained together, and the remaining data is passed on to the next. In this way, you can easily control the color of many LEDs using a single GPIO.

Usage :id=usage

In most cases, the WS2812 driver code is automatically included if you are using either the RGBLight or RGB Matrix feature with the ws2812 driver set, and you would use those APIs instead.

However, if you need to use the driver standalone, add the following to your rules.mk:

WS2812_DRIVER_REQUIRED = yes

You can then call the WS2812 API by including ws2812.h in your code.

Basic Configuration :id=basic-configuration

Add the following to your config.h:

Define Default Description
WS2812_DI_PIN Not defined The GPIO pin connected to the DI pin of the first LED in the chain
WS2812_LED_COUNT Not defined Number of LEDs in the WS2812 chain - automatically set when RGBLight or RGB Matrix is configured
WS2812_TIMING 1250 The total length of a bit (TH+TL) in nanoseconds
WS2812_T1H 900 The length of a "1" bit's high phase in nanoseconds
WS2812_T0H 350 The length of a "0" bit's high phase in nanoseconds
WS2812_TRST_US 280 The length of the reset phase in microseconds
WS2812_BYTE_ORDER WS2812_BYTE_ORDER_GRB The byte order of the RGB data
WS2812_RGBW Not defined Enables RGBW support (except i2c driver)

Timing Adjustment :id=timing-adjustment

The WS2812 LED communication protocol works by encoding a "1" bit with a long high pulse (T1H), and a "0" bit with a shorter pulse (T0H). The total cycle length of a bit is the same. The "reset" pulse (TRST) latches the sent RGB data to all of the LEDs and denotes a completed "frame".

Some WS2812 variants have slightly different timing parameter requirements, which can be accounted for if necessary using the above #defines in your config.h.

Byte Order :id=byte-order

Some WS2812 variants may have their color components in a different physical or logical order. For example, the WS2812B-2020 has physically swapped red and green LEDs, which causes the wrong color to be displayed, because the default order of the bytes sent over the wire is defined as GRB. If you find your LED colors are consistently swapped, you may need to change the byte order by adding the following to your config.h:

#define WS2812_BYTE_ORDER WS2812_BYTE_ORDER_GRB

Where the byte order may be one of:

Byte Order Known Devices
GRB Most WS2812s, SK6812, SK6805
RGB WS2812B-2020
BGR TM1812

RGBW Support :id=rgbw-support

Rendering the color white with RGB LEDs is typically inconsistent due to inherent variations between each individual LED die. However, some WS2812 variants (such as SK6812RGBW) also possess a white LED along with the red, green, and blue channels, which allows for a more accurate white to be displayed.

QMK can automatically convert the RGB data to be sent to the LEDs to mix in the white channel:

w = min(r, g, b)
r -= w
g -= w
b -= w

Thus, an RGB triplet of 255,255,255 will simply turn on the white LED fully (0,0,0,255).

To enable RGBW conversion, add the following to your config.h:

#define WS2812_RGBW

Driver Configuration :id=driver-configuration

Driver selection can be configured in rules.mk as WS2812_DRIVER, or in info.json as ws2812.driver. Valid values are bitbang (default), i2c, spi, pwm, vendor, or custom. See below for information on individual drivers.

Bitbang Driver :id=bitbang-driver

This is the default WS2812 driver. It operates by "bit-banging" ie. directly toggling the GPIO.

Please note that on AVR devices, due to the tight timing requirements longer chains and/or heavy CPU loads may cause visible lag. Unfortunately this driver is usually the only option for AVR.

WS2812_DRIVER = bitbang

I2C Driver :id=i2c-driver

A specialized driver mainly used for PS2AVRGB (Bootmapper Client) boards, which possess an ATtiny85 that handles the WS2812 LEDs.

WS2812_DRIVER = i2c

The following #defines apply only to the i2c driver:

Define Default Description
WS2812_I2C_ADDRESS 0xB0 The I2C address of the ATtiny85.
WS2812_I2C_TIMEOUT 100 The I2C timeout, in milliseconds.

PIO Driver :id=pio-driver

This driver is RP2040-only, and leverages the onboard PIO (programmable I/O) system and DMA to offload processing from the CPU.

The WS2812 PIO program uses one state machine, six instructions and one DMA interrupt handler callback. Due to the implementation the time resolution for this driver is 50 ns - any value not specified in this interval will be rounded to the next matching interval.

WS2812_DRIVER = vendor

PWM Driver :id=pwm-driver

This driver is ARM-only, and leverages the onboard PWM peripheral and DMA to offload processing from the CPU.

WS2812_DRIVER = pwm

SPI Driver :id=spi-driver

This driver is ARM-only, and leverages the onboard SPI peripheral and DMA to offload processing from the CPU. The DI pin must be connected to the MOSI pin on the MCU, and all other SPI pins must be left unused. This is also very dependent on your MCU's SPI peripheral clock speed, and may or may not be possible depending on the MCU selected.

WS2812_DRIVER = spi

ChibiOS/ARM Configuration :id=arm-configuration

The following defines apply only to ARM devices:

Define Default Description
WS2812_T1L (WS2812_TIMING - WS2812_T1H) The length of a "1" bit's low phase in nanoseconds (bitbang and PIO drivers only)
WS2812_T0L (WS2812_TIMING - WS2812_T0H) The length of a "0" bit's low phase in nanoseconds (bitbang and PIO drivers only)

Push-Pull and Open Drain :id=push-pull-open-drain

By default, the GPIO used for data transmission is configured as a push-pull output, meaning the pin is effectively always driven either to VCC or to ground.

For situations where the logic level voltage is lower than the power supply voltage, however, this can pose an issue. The solution is to configure the pin for open drain mode instead, and use a pullup resistor between the DI pin and VCC. In this mode, the MCU can only pull the GPIO low, or leave it floating. The pullup resistor is then responsible for pulling the line high, when the MCU is not driving the GPIO.

To configure the DI pin for open drain configuration, add the following to your config.h:

#define WS2812_EXTERNAL_PULLUP

SPI Driver :id=arm-spi-driver

Depending on the ChibiOS board configuration, you may need to enable SPI at the keyboard level. For STM32, this would look like:

halconf.h:

#define HAL_USE_SPI TRUE

mcuconf.h:

#undef STM32_SPI_USE_SPI1
#define STM32_SPI_USE_SPI1 TRUE

The following defines apply only to the spi driver:

Define Default Description
WS2812_SPI_DRIVER SPID1 The SPI driver to use
WS2812_SPI_MOSI_PAL_MODE 5 The MOSI pin alternative function to use
WS2812_SPI_SCK_PIN Not defined The SCK pin - required for F072 and possibly others
WS2812_SPI_SCK_PAL_MODE 5 The SCK pin alternative function to use - required for F072 and possibly others
WS2812_SPI_DIVISOR 16 The divisor used to adjust the baudrate
WS2812_SPI_USE_CIRCULAR_BUFFER Not defined Enable a circular buffer for improved rendering

Setting the Baudrate :id=arm-spi-baudrate

To adjust the SPI baudrate, you will need to derive the target baudrate from the clock tree provided by STM32CubeMX, and add the following to your config.h:

#define WS2812_SPI_DIVISOR 16

Only divisors of 2, 4, 8, 16, 32, 64, 128 and 256 are supported on STM32 devices. Other MCUs may have similar constraints -- check the reference manual for your respective MCU for specifics.

Circular Buffer :id=arm-spi-circular-buffer

A circular buffer can be enabled if you experience flickering.

To enable the circular buffer, add the following to your config.h:

#define WS2812_SPI_USE_CIRCULAR_BUFFER

PIO Driver :id=arm-pio-driver

The following #defines apply only to the PIO driver:

Define Default Description
WS2812_PIO_USE_PIO1 Not defined Use the PIO1 peripheral instead of PIO0

PWM Driver :id=arm-pwm-driver

Depending on the ChibiOS board configuration, you may need to enable PWM at the keyboard level. For STM32, this would look like:

halconf.h:

#define HAL_USE_PWM TRUE

mcuconf.h:

#undef STM32_PWM_USE_TIM2
#define STM32_PWM_USE_TIM2 TRUE

The following #defines apply only to the pwm driver:

Define Default Description
WS2812_PWM_DRIVER PWMD2 The PWM driver to use
WS2812_PWM_CHANNEL 2 The PWM channel to use
WS2812_PWM_PAL_MODE 2 The pin alternative function to use
WS2812_PWM_DMA_STREAM STM32_DMA1_STREAM2 The DMA Stream for TIMx_UP
WS2812_PWM_DMA_CHANNEL 2 The DMA Channel for TIMx_UP
WS2812_PWM_DMAMUX_ID Not defined The DMAMUX configuration for TIMx_UP - only required if your MCU has a DMAMUX peripheral
WS2812_PWM_COMPLEMENTARY_OUTPUT Not defined Whether the PWM output is complementary (TIMx_CHyN)

?> Using a complementary timer output (TIMx_CHyN) is possible only for advanced-control timers (1, 8 and 20 on STM32), and the STM32_PWM_USE_ADVANCED option in mcuconf.h must be set to TRUE. Complementary outputs of general-purpose timers are not supported due to ChibiOS limitations.

API :id=api

void ws2812_setleds(rgb_led_t *ledarray, uint16_t number_of_leds) :id=api-ws2812-setleds

Send RGB data to the WS2812 LED chain.

Arguments :id=api-ws2812-setleds-arguments

  • rgb_led_t *ledarray
    A pointer to the LED array.
  • uint16_t number_of_leds
    The length of the LED array.