Software firefly

It's another parts-on-hand project.   A white LED connected to an output bit on a microcontroller.   Ill use the Arduino Pro Mini because they're cheap and I have a few "in stock" in the garage.   It's basically a Microchip (formerly Atmel) ATmega328P single chip microcomputer on a board. They're $4 in five-packs on Amazon, $2 direct from Asia but take your chances with Chinese counterfeit chips.

Oh no! The only white indicator LEDs I have on hand are tiny "0805" (0.08 x 0.05 inch) surface mount dudes.   All my attempts to solder wires to these tiny parts fail.   They must sit on a board.   We have tiny "breakout" boards for that.  For scale, the big round holes are 0.1 inch center to center.  

The pro mini has a regulator so it can run off a 9V battery.  Or it can run off 3 to 5 volts bypassing the regulator.   Circuit looks like:

and here's the firefly assembly.

We use the Arduino integrated development system because it's easy with a big support ecosystem.  Arduino IDE talks to the Pro Mini board through a USB to 5V serial adapter.  The five wires are Ground, +5V power to Pro Mini, serial data from PC, serial data to PC, and "DTR."   The DTR signal is no longer used for serial ports, and Arduino uses it to signal a hardware reset to the ATmega328P.  

This is a complete hobby scale microcontroller development system.   Usable from Windoz, Linux, or Macos.   Windoz and mac will make you hunt for drivers.   With Linux, it just plugs in and works.   

Here's a sketch to blink like a firefly.   Work in progress, still needs a low power sleep  function to be practical.   

//   Arduino Pro Mini   with some LEDs tacked on

// The yellow LED is connected between GPIO2 and VCC.

//  (Of course with a current limiting resistor.)

//  So LOW gives lit up and HIGH gives dark.

#define yellow   2

#define white    4 

#define blue    10

char  yel;  //  nonzero means yellow LED is on.

int   onesec; 

unsigned long delayer;   //millis

int   enth;  // do it the nth time.

int   enthb;

char  rq;   //  request a flash,

char  rqb;   //  request a blue flash,

void setup() {

  char ix;

  cli();

  yel =0;  //  off 

  for (ix=2; ix < 13;  ix++){

    pinMode(ix,  INPUT_PULLUP);

  }

  pinMode(yellow,  OUTPUT);

  digitalWrite(yellow, HIGH);

  pinMode(green,  OUTPUT);

  digitalWrite(green, HIGH);

  pinMode(13,  OUTPUT);

  //   timer 1 1Hz

  TCCR1A = 0;// set entire TCCR1A register to 0

  TCCR1B = 0;// same for TCCR1B

  TCNT1  = 0;//initialize counter value to 0

  // set compare match register for 1hz increments

  OCR1A = 15624;// = (16*10^6) / (1*1024) - 1 (must be <65536)

  // turn on CTC mode

  TCCR1B |= (1 << WGM12);

  // Set CS10 and CS12 bits for 1024 prescaler

  TCCR1B |= (1 << CS12) | (1 << CS10);  

  // enable timer compare interrupt

  TIMSK1 |= (1 << OCIE1A);

  onesec=0;

  rq=0;

  rqb=0;

  enth=0;

  sei();

}

ISR(TIMER1_COMPA_vect){

  timer1service();

}

void timer1service(){   //  1 Hz timer

  onesec++;

  enth++;

  enthb++;

  if( enth > 5 ) {        // blink every five secs.

    rq=1;

    enth =0;

  }

  if( enthb > 31 ) {     //blink the other one every 31 sec.

    rqb=1;

    enthb =0;

  }

  

  

}

void firefly(){

  char iy, iz;

  for( iy=1; iy<6;  iy++){

    digitalWrite(yellow, LOW);

    delay(20);

    digitalWrite(yellow, HIGH);

    delay(30);

  }

}

void blueflash(){

  char iy, iz;

  for( iy=1; iy<6;  iy++){

    digitalWrite(green, LOW);

    delay(20);

    digitalWrite(green, HIGH);

    delay(100);

  }

}

void loop() {

  // put your main code here, to run repeatedly:

  if( rq ){

    firefly();

    rq=0;

  }

  if( rqb ){

    blueflash();

    rqb=0;

  }

  

 

  

  delay(100);   //   Need a low power sleep here

}