WS2812

We all love colorful blinking LEDs, right? There’s a simple API for accessing the five individually addressable RGB LEDs on the Badge’s kite. The API is found inside a separate ESP-IDF compontent ws2812 that is intended as a [git submodule] (https://github.com/badgeteam/esp32-component-ws2812). If you started your app development from the [template app] (https://github.com/badgeteam/mch2022-template-app), it should be already set up.

There’s a sixth RGB LED on the board (next to the top corner of the display). This LED is controlled via the ICE40 FPGA (see its driver for details).

The LEDs are WS2812-compatible. If you’re not already familiar with these LEDs: Each LED contains red, green and blue LED and a tiny controller that receives 24 bit RGB data from a single serial data line. Further data bits are pushed through to its data output, which is connected to the next LED. This allows many LEDs in a string to be individually controlled.

The LED power supply is switched (together with the SD card). Before using the LEDs, set IO19 (GPIO_SD_PWR) to 1.

Before controlling the LEDs, the driver has to be set up with the data line connected to the LEDs (GPIO_LED_DATA). If you want to control other WS2812 LEDs (e.g. connected to one of the extension connectors), you can specify a different value.

Setting the LEDs is pretty straightforward: Set up an array of 15 unsigned brightness values (R,G,B for 5 LEDs).

A minimal example to set all LEDs to red:

  uint8_t red[] = {0,255,0,0,255,0,0,255,0,0,255,0,0,255,0};
  // turn on LED power
  gpio_set_direction(GPIO_SD_PWR, GPIO_MODE_OUTPUT);
  gpio_set_level(GPIO_SD_PWR, 1);
  // initialize WS2812 driver to the appropriate data pin
  ws2812_init(GPIO_LED_DATA);
  ws2812_send_data(red, sizeof(red));

To animate, change the array values and repeat ws2812_send_data in regular intervals.

Last modified July 23, 2022: Fix WS2812 Example (1c68bab)