Sounding a Piezo Buzzer

 1234567891011121314151617 void buzz(int targetPin, long frequency, long length) {   long delayValue = 1000000/frequency/2;   // calculate the delay value between transitions   //// 1 second's worth of microseconds, divided by the frequency,   //// then split in half since there are two phases to each cycle   long numCycles = frequency * length/ 1000;   // calculate the number of cycles for proper timing   //// multiply frequency, which is really cycles per second, by the   //// number of seconds to get the total number of cycles to produce  for (long i=0; i < numCycles; i++){ // for the calculated length of time...     digitalWrite(targetPin,HIGH); // write the buzzer pin high to push out the diaphram     delayMicroseconds(delayValue); // wait for the calculated delay value     digitalWrite(targetPin,LOW); // write the buzzer pin low to pull back the diaphram     delayMicroseconds(delayValue); // wait again for the calculated delay value   } }

Check Amount Of Free RAM

 1234567891011121314151617 // this function will return the number of bytes currently free in RAM int memoryTest() {   int byteCounter = 0; // initialize a counter   byte *byteArray; // create a pointer to a byte array   // More on pointers here: http://en.wikipedia.org/wiki/Pointer#C_pointers (external link)   // use the malloc function to repeatedly attempt   // allocating a certain number of bytes to memory   // More on malloc here: http://en.wikipedia.org/wiki/Malloc (external link)   while ( (byteArray = (byte*) malloc (byteCounter * sizeof(byte))) != NULL ) {     byteCounter++; // if allocation was successful, then up the count for the next try     free(byteArray); // free memory after allocating it   }   free(byteArray); // also free memory after the function finishes   return byteCounter; // send back the highest number of bytes successfully allocated }

Display the value of a 10K potentimeter to the serial console.

 123456789101112131415161718192021 /* Display the value of a 10K potentimeter to the serial console. Copyright: Systemchimp.com 2007 */ /* The analog pin connect to pot. */ int p1 = 2; int p1_val = 0;   void setup() {   pinMode(p1, INPUT);   Serial.begin(9600); }   void loop() {   p1_val = analogRead(p1);   Serial.print("P1=");   Serial.println(p1_val, DEC);   delay(1000); }