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Orbit-Q: Controlling Onboard WS2812B RGB LEDs

This tutorial covers how to control the onboard array of 10 WS2812B addressable RGB LEDs using the Orbit-Q STM32F405 card. We will use the Arduino IDE and the widely supported Adafruit NeoPixel library to send data out via the designated GPIO pin.

1. Hardware Connections & Jumper Configuration

According to the "Orbit-Q Datasheet.pdf", JP-1 is a 2x2 configuration header used to connect the LED array to the microcontroller and the onboard power supply[cite: 1]. Two jumper caps are required on this header for normal operation[cite: 1]:

  • Data Jumper: Connect the GPIO pin to the DI (Data-In) pin[cite: 1]. The LED array receives serial data from the microcontroller through this GPIO-to-DI connection established by JP1[cite: 1].
  • Power Jumper: Connect the 5V IN pin to the LED 5V pin[cite: 1]. Power is supplied from the onboard 5 V regulator through the 5V IN-to-LED 5V connection[cite: 1].
  • Both connections must be present for normal operation[cite: 1].

Check Your Jumpers

If the JP-1 jumpers are missing, the LEDs will not receive power from the board's 5V rail or data from the STM32F405, and your code will appear to do nothing.

2. Installing the Library

We will use the Adafruit NeoPixel library to handle the strict timing requirements of the WS2812B protocol.

  1. Open the Arduino IDE.
  2. Navigate to Sketch > Include Library > Manage Libraries (or press Ctrl + Shift + I).
  3. In the Library Manager search bar, type Adafruit NeoPixel.
  4. Locate the library by Adafruit and click Install.

3. Arduino Sketch

Copy and paste the following code into your Arduino IDE. This sketch initializes the 10 onboard LEDs and cycles them through basic primary colors in a "wipe" animation.

#include <Adafruit_NeoPixel.h>

// Define the STM32 pin connected to the WS2812B data input
#define LED_PIN    PB3

// Define the number of LEDs in the chain
#define LED_COUNT  10

// Initialize the NeoPixel object
// NEO_GRB + NEO_KHZ800 is the standard configuration for WS2812B LEDs
Adafruit_NeoPixel strip(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  // Initialize the NeoPixel library
  strip.begin();

  // Set brightness to ~20% (Value from 0 to 255) to limit current draw
  strip.setBrightness(50); 

  // Update the strip to ensure all LEDs are turned off on startup
  strip.show(); 
}

void loop() {
  // Wipe Red
  colorWipe(strip.Color(255, 0, 0), 50);

  // Wipe Green
  colorWipe(strip.Color(0, 255, 0), 50);

  // Wipe Blue
  colorWipe(strip.Color(0, 0, 255), 50);

  // Wipe Off (Black)
  colorWipe(strip.Color(0, 0, 0), 50);
}

// Function to fill the dots one after the other with a color
void colorWipe(uint32_t color, int wait) {
  for(int i = 0; i < strip.numPixels(); i++) { 
    strip.setPixelColor(i, color);         // Set pixel 'i' to the specified color
    strip.show();                          // Push the updated color to the hardware
    delay(wait);                           // Pause for a moment
  }
}

4. Code Explanation

  • Adafruit_NeoPixel strip(...): This creates the software object representing your LED strip. We pass it LED_COUNT (10) and LED_PIN (PB3).
  • strip.begin(): Allocates memory and sets up the STM32 GPIO pin for output.
  • strip.setBrightness(50): Caps the maximum brightness (0-255).
  • strip.Color(R, G, B): Packs Red, Green, and Blue values (0-255 each) into a single 32-bit variable that the library understands.
  • strip.setPixelColor(index, color): Updates the color of a specific LED in the MCU's RAM. index starts at 0 (so the 10th LED is index 9).
  • strip.show(): The STM32 sends the stored RAM data out to physically update the LEDs. You must call this for changes to become visible.

5. Uploading to the Orbit-Q

  • Put the Orbit-Q into bootloader mode (Slide Boot Switch to BOOT / ONand press RESET).
  • Select your COM port or USB DFU interface.
  • Ensure the board is set to Generic STM32F4 series with part number STM32F405RGTx.
  • Click Upload.
  • Once complete, switch the Boot Slide Switch back to NORMAL / OFF and press RESET to run your LED code.

Troubleshooting

LEDs are not turning on or acting erratically
  • Check JP-1 Jumpers: Ensure both the GPIO-to-DI and 5V IN-to-LED 5V jumper caps are securely seated on the JP-1 header.
  • Power Issues: If the LEDs turn red or the STM32 resets randomly, the LEDs are drawing too much current from your USB port. Lower strip.setBrightness() in the code to 10 or 20.