Simple Arduino Sanity Check

Folks - here's a quick sketch I wrote that can be used to check that an arduino is basically ok without needing any circuitry other than your USB connection. It:

• uses the internal LED for "blink sketch" like behavior - basically a 50% duty cycle blink.
• avoids using delays and instead uses millis() to blink the LED.
• accepts a numerical input from the serial port to set the blink rate of the LED in Hz

That's all. Just thought some folks might find it helpful.

/* Arduino Sanity Test */
/* Uses the internal LED and serial port to ensure unit is basically ok */

/* Global Variables */
unsigned long PreviousMillis;
unsigned char BuiltInLED = LOW; // LOW=off, HIGH=on

int BlinkFrequency = 2; // LED blink frequency in Hz
int ToggleRate = 500 / BlinkFrequency; // ms per half cycle toggle

String SerialInput; // Any input from serial port


void setup() {
   // Serial Port initialization
   Serial.begin(9600);

   // Setup the internal LED pin
   pinMode( LED_BUILTIN, OUTPUT );

   /* Start counting millis until first toggle */
   PreviousMillis = millis();

}

void loop() {

   // Get input from serial port, convert to int, set as blink frequency
   if( Serial.available() ) {
       
       // Get input string
       SerialInput = Serial.readStringUntil('\n');

       // Feedback to serial port
       Serial.print("Blink rate set to " );
       Serial.print(SerialInput);
       Serial.println(" Hz.");

       // Set blink rates
       BlinkFrequency = SerialInput.toInt();
       ToggleRate = 500 / BlinkFrequency;
   }

   // determine if sufficient time has elapsed and if so, toggle LED
   if( millis() - PreviousMillis >= ToggleRate ) {
     
       // Flip LED State and reset previous
       BuiltInLED = (BuiltInLED == HIGH) ? LOW : HIGH;
       digitalWrite( LED_BUILTIN, BuiltInLED );

       PreviousMillis = millis();
   }

   delay(1); // 1ms delay at loop bottom
}