itone_for_esp.ino

/*
    ESP8266 example for tone via timer1
    Hardware: NodeMCU
    2018
    tone using Timer
*/

//define ITONE_CYCLE 2500000 // 1 second cycle in 1/16 CPU clock (1/5 µs) for 80 MHz
#define ITONE_CYCLE 5000000  // 1 second cycle in 1/16 CPU clock (1/5 µs) for 160 MHz
 
//=======================================================================
//       itone, noItone
//=======================================================================
byte _itonepin = D0;
byte _itoneval = HIGH;

void ICACHE_RAM_ATTR _onItoneTimerISR(){
  _itoneval ^= 1;
  digitalWrite(_itonepin,_itoneval);  //Toggle LED Pin
}
void itone(byte pin,unsigned long frequency) {
  timer1_detachInterrupt();
  timer1_attachInterrupt(_onItoneTimerISR);
  timer1_enable(TIM_DIV16, TIM_EDGE, TIM_LOOP);
  _itoneval = HIGH;
  _itonepin = pin;
  pinMode(pin,OUTPUT);
  digitalWrite(pin,HIGH);
  timer1_write(ITONE_CYCLE/frequency);
}

void noItone() {
  timer1_detachInterrupt();
}

//=======================================================================
//                               Setup
// we test the serial connection during itone running
// result: it still works
//=======================================================================
void setup()
{
  Serial.begin(115200);
  itone(D0,2000); // LED blinks with 1 Hz
  delay(3000);
  noItone();
  
}
//=======================================================================
//                MAIN LOOP
//=======================================================================
void loop()
{
}