COB LED Driver Board — XIAO Accessory Guide

Compatible XIAO Boards

Pin Usage Diagram

XIAO Pin    | Accessory Function         | Protocol
------------|----------------------------|----------
D0          | High-Power Port            | GPIO (ON/OFF only, 300mA max)
D1          | High-Power Port            | GPIO (ON/OFF only, 300mA max)
D2          | Low-Power Port (PWM)       | GPIO/PWM (Active LOW, 80mA max)
D3          | Low-Power Port (PWM)       | GPIO/PWM (Active LOW, 80mA max)
D8          | Low-Power Port (PWM)       | GPIO/PWM (Active LOW, 80mA max)
D9          | Low-Power Port (PWM)       | GPIO/PWM (Active LOW, 80mA max)
SDA         | I²C Grove connector        | I2C
SCL         | I²C Grove connector        | I2C
VCC         | Always-On Port             | Power (300mA max, not switch-controlled)

Pin Conflict Warning

Pins OCCUPIED by COB LED Driver

• D0 — High-Power Port
• D1 — High-Power Port
• D2 — Low-Power PWM Port
• D3 — Low-Power PWM Port
• D8 — Low-Power PWM Port
• D9 — Low-Power PWM Port
• SDA/SCL — I²C Grove connector

Pins remaining FREE

• D4 (if not using I2C Grove), D5 (if not using I2C Grove), D6, D7, D10, A0

Conflicts with other accessories

• ePaper Driver Board — conflicts on D0, D1, D2, D3, D8 ❌
• Expansion Board Base — conflicts on D1 (button), D2 (SD CS), D3 (buzzer), D8 (SPI SCK), D9 (SPI MISO) ❌
• RS485 Board — conflicts on D2 (enable) ❌
• CAN Bus Board — conflicts on D8, D9 (SPI) ❌
• Grove Vision AI V2 — can share I2C bus ✅ (uses SDA/SCL only)

Note: This board uses 6 GPIO pins plus I2C. It is designed to be used as the primary accessory, not stacked with other GPIO-heavy boards.

Power Requirements

⚠️ Do NOT use USB and battery simultaneously with peripherals connected.

Arduino Setup & Usage

Required Libraries

None — direct GPIO control, no extra libraries needed.

Initialization

// High-Power Ports (D0, D1) — Active HIGH, ON/OFF only, 300mA max
// Low-Power Ports (D2, D3, D8, D9) — Active LOW, PWM capable, 80mA max

void setup() {
    // High-Power ports
    pinMode(D0, OUTPUT);
    pinMode(D1, OUTPUT);

    // Low-Power PWM ports
    pinMode(D2, OUTPUT);
    pinMode(D3, OUTPUT);
    pinMode(D8, OUTPUT);
    pinMode(D9, OUTPUT);
}

Complete Working Example — High-Power Port Control

// Control high-power LED ports (D0, D1)
// Active HIGH: HIGH = ON, LOW = OFF
// Max 300mA per channel, NO PWM support

void setup() {
    pinMode(D0, OUTPUT);
    pinMode(D1, OUTPUT);
}

void loop() {
    // Turn on both high-power channels
    digitalWrite(D0, HIGH);  // LED ON
    digitalWrite(D1, HIGH);  // LED ON
    delay(2000);

    // Turn off both high-power channels
    digitalWrite(D0, LOW);   // LED OFF
    digitalWrite(D1, LOW);   // LED OFF
    delay(1000);
}

Complete Working Example — Low-Power PWM Dimming

// Control low-power LED ports with PWM dimming
// Active LOW: LOW = full brightness, HIGH = OFF
// Max 80mA per channel

void setLedBrightness(int pin, int brightness) {
    brightness = constrain(brightness, 0, 255);
    int pwmValue = 255 - brightness;  // Active LOW inversion
    analogWrite(pin, pwmValue);
}

void setup() {
    pinMode(D2, OUTPUT);
    pinMode(D3, OUTPUT);
    pinMode(D8, OUTPUT);
    pinMode(D9, OUTPUT);
}

void loop() {
    // Breathing effect on D2
    for (int i = 0; i <= 255; i++) {
        setLedBrightness(D2, i);
        delay(5);
    }
    for (int i = 255; i >= 0; i--) {
        setLedBrightness(D2, i);
        delay(5);
    }
}

Complete Working Example — All Channels

void setLedBrightness(int pin, int brightness) {
    brightness = constrain(brightness, 0, 255);
    int pwmValue = 255 - brightness;  // Active LOW inversion
    analogWrite(pin, pwmValue);
}

void setup() {
    // High-Power ports (ON/OFF only)
    pinMode(D0, OUTPUT);
    pinMode(D1, OUTPUT);

    // Low-Power PWM ports
    pinMode(D2, OUTPUT);
    pinMode(D3, OUTPUT);
    pinMode(D8, OUTPUT);
    pinMode(D9, OUTPUT);

    // Turn on high-power channels
    digitalWrite(D0, HIGH);
    digitalWrite(D1, HIGH);
}

void loop() {
    // Cycle through PWM channels
    int pwmPins[] = {D2, D3, D8, D9};

    for (int ch = 0; ch < 4; ch++) {
        setLedBrightness(pwmPins[ch], 200);  // ~80% brightness
        delay(500);
        setLedBrightness(pwmPins[ch], 0);    // OFF
    }
}

TinyGo Setup & Usage

No special drivers needed — direct GPIO/PWM control.

TinyGo High-Power Port Example

package main

import (
    "machine"
    "time"
)

func main() {
    // High-Power ports: Active HIGH, ON/OFF only
    d0 := machine.D0
    d1 := machine.D1
    d0.Configure(machine.PinConfig{Mode: machine.PinOutput})
    d1.Configure(machine.PinConfig{Mode: machine.PinOutput})

    for {
        d0.High() // LED ON
        d1.High() // LED ON
        time.Sleep(2 * time.Second)

        d0.Low()  // LED OFF
        d1.Low()  // LED OFF
        time.Sleep(1 * time.Second)
    }
}

TinyGo PWM Dimming Example

package main

import (
    "machine"
    "time"
)

func main() {
    // Low-Power ports: Active LOW, PWM capable
    // Configure PWM for D2
    pwm := machine.PWM0 // Adjust PWM peripheral for your XIAO board
    err := pwm.Configure(machine.PWMConfig{
        Period: 1e6, // 1ms period (1kHz)
    })
    if err != nil {
        println("PWM config error:", err.Error())
        return
    }

    ch, err := pwm.Channel(machine.D2)
    if err != nil {
        println("PWM channel error:", err.Error())
        return
    }

    // Breathing effect (Active LOW: 0 = full brightness, max = OFF)
    top := pwm.Top()
    for {
        // Fade in (decrease duty for active LOW)
        for i := uint32(0); i < top; i += top / 256 {
            pwm.Set(ch, top-i) // Invert for active LOW
            time.Sleep(5 * time.Millisecond)
        }
        // Fade out (increase duty for active LOW)
        for i := uint32(0); i < top; i += top / 256 {
            pwm.Set(ch, i) // Invert for active LOW
            time.Sleep(5 * time.Millisecond)
        }
    }
}

Note: PWM peripheral assignment varies by XIAO board. Check the board-specific skill for correct PWM peripheral mappings.

Communication Protocol Details

GPIO Control

Active LOW Behavior (Low-Power Ports)

I2C (Grove Connector)

Common Gotchas / Notes

1. ⚠️ Hot-plugging is strictly prohibited! Assemble XIAO and driver board first, then plug USB cable.
2. ⚠️ Do not connect peripherals during charging — Disconnect LED strips before plugging USB-C for charging.
3. ⚠️ When debugging via USB-C, battery holder must be empty.
4. Active LOW on PWM ports — Pull pin LOW to turn strip ON. This is the opposite of typical LED control. Use 255 - brightness for PWM values.
5. High-Power ports are ON/OFF only — D0 and D1 do NOT support PWM dimming.
6. VCC port is always on — The VCC port (300mA) is not switch-controlled and cannot be turned off in software.
7. Heat dissipation — For full load currents >1A total, ensure heat dissipation holes in any housing.
8. ESD risk — Never touch the PMIC area on the back of the board (ESD risk, high temperature during operation).
9. ESPHome support — Also supports ESPHome for Home Assistant integration.

Reference Links

• Seeed Wiki: https://wiki.seeedstudio.com/getting_started_with_cob_led_dirver_board/
• Product Page: https://www.seeedstudio.com/COB-LED-Driver-Board-for-Seeed-Studio-XIAO-p-6602.html