12 KiB
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 |
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 |
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_DMA_STREAM |
STM32_DMA1_STREAM2 |
The DMA Stream for TIMx_UP |
WS2812_DMA_CHANNEL |
2 |
The DMA Channel for TIMx_UP |
WS2812_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.