APA102 Sample Application

Overview

This sample application demonstrates basic usage of the APA102 LED strip driver, for controlling LED strips using APA102, Adafruit DotStar, and compatible driver chips.

Requirements

  • LED strip using APA102 or compatible, such as the any Dotstar product from AdaFruit.
  • Zephyr board with SPI master driver. SPI communications must use 5V signaling, which may require a level translator, such as the 74AHCT125.
  • 5V power supply.

Wiring

  1. Ensure your Zephyr board, the 5V power supply, and the LED strip share a common ground.
  2. Connect the MOSI pin of your board’s SPI master to the data input pin of the first APA102 IC in the strip.
  3. Connect the SCLK pin of your board’s SPI master to the clock input pin of the first APA102 IC in the strip.
  4. Connect the 5V power supply pin to the 5V input of the LED strip.

Building and Running

The sample application is located at samples/drivers/led_apa102/ in the Zephyr source tree.

Configure For Your Board

Now check if your board is already supported, by looking for a file named boards/YOUR_BOARD_NAME.conf in the application directory.

If your board isn’t supported yet, you’ll need to configure the application as follows.

  1. Configure your board’s SPI master in a configuration file under boards/ in the sample directory.

    To provide additional configuration for some particular board, create a boards/YOUR_BOARD_NAME.conf file in the application directory. It will be merged into the application configuration.

    In this file, you must ensure that the SPI peripheral you want to use for this demo is enabled. See boards/nucleo_l432kc.conf for an example.

    #. Configure your board’s dts overlay. See nucleo_l432kc.overlay for an example.

  2. Set the number of LEDs in your strip in the application sources. This is determined by the macro STRIP_NUM_LEDS in the file src/main.c.

Then build and flash the application:

# On Linux/macOS
cd $ZEPHYR_BASE/samples/drivers/led_apa102
mkdir build && cd build
# On Windows
cd %ZEPHYR_BASE%\samples\drivers\led_apa102
mkdir build & cd build
cmake -GNinja -DBOARD=<board> ..
ninja flash

Refer to your board’s documentation for alternative flash instructions if your board doesn’t support the flash target.

When you connect to your board’s serial console, you should see the following output:

***** BOOTING ZEPHYR OS zepyhr-v1.13.XX *****
[general] [INF] main: Found LED strip device APA102