Reference: DIY USB Examples

1. Have its own power source separate from Sidekick so that it is powered on and running all the time to monitor the incoming power.
   1. The Sidekick USB A port must be connected to your hardware to be monitored for 5V power.
   2. When your DIY board detects power coming from the USB A port, you can perform any function of your choosing.
   3. When your DIY board detects that power from the USB A port has stopped (alert snoozed/stopped), you can perform another function.
2. Run on USB A, 5V, 1 Amp or less and automatically perform your dedicated functions when powered on.
   1. Plug your external hardware into Sidekick’s USB A port.
   2. If your hardware connects to WiFi, bluetooth, or has other delayed startup functions, you should only use the first DIY option above to ensure the alert function you have programmed runs immediately.

USB 5V → [20kΩ] → GPIO 18
           ↓
        [10kΩ] → GND

const int usbPowerPin = 18;  // GPIO18 gets the divided signal
bool lastState = LOW;

void setup() {
  pinMode(usbPowerPin, INPUT);
  Serial.begin(115200);
}

void loop() {
  bool currentState = digitalRead(usbPowerPin);
  if (currentState != lastState) {
    if (currentState == HIGH) {
      Serial.println("USB Power ON");
      // YOUR ALERT START CODE GOES HERE
    } else {
      Serial.println("USB Power OFF");
      // YOUR ALERT STOP CODE GOES HERE
    }
    lastState = currentState;
  }
  delay(100); // debounce / polling delay
}

const int usbPowerPin = 2;  // USB 5V line connected here
bool lastState = LOW;

void setup() {
  pinMode(usbPowerPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  bool currentState = digitalRead(usbPowerPin);
  if (currentState != lastState) {
    if (currentState == HIGH) {
      Serial.println("USB Power ON");
      // YOUR ALERT START CODE GOES HERE
    } else {
      Serial.println("USB Power OFF");
      // YOUR ALERT STOP CODE GOES HERE
    }
    lastState = currentState;
  }
  delay(100); // debounce / polling delay
}

​

Example DIY Integrations