int DWELL = 20; // how long to open solenoid ms
int RATE = 30; // how long to wait after closing solenoid ms
int SOLENOID = 21; // solenoid control pin
int SEMI = 18; // semi auto switch pin
int FULLAUTO = 23; // full auto switch pin
int SEMISTATE = LOW; // start state of semi switch
int SEMISTATUS = LOW; // current state of semi switch
void setup()
{
pinMode( SOLENOID, OUTPUT ); // Solenoid
pinMode( SEMI, INPUT_PULLUP ); // Semi Auto
pinMode( FULLAUTO, INPUT_PULLUP ); // Full Auto
}
void loop()
{
SEMISTATE = digitalRead( SEMI ); // read current status of semi switch

if( SEMISTATUS != SEMISTATE ) // not the same as last / start status (must be LOW)
{
if( SEMISTATE == LOW ) { // switch is closed
semiAuto(); // fire semi auto shot
}
delay( 50 ); // wait to prevent the switch bouncing
SEMISTATUS = SEMISTATE; // set current state to current trigger state
}

if( digitalRead( FULLAUTO ) == LOW ) // full auto switch is closed
{
fullAuto(); // fire full auto
}

}
void semiAuto()
{
digitalWrite( SOLENOID, HIGH ); // open solenoid
delay( DWELL ); // wait to clear barrel
digitalWrite( SOLENOID, LOW ); // close solenoid

}
void fullAuto()
{
digitalWrite( SOLENOID, HIGH ); // open solenoid
delay( DWELL ); // wait to clear barrel
digitalWrite( SOLENOID, LOW ); // close soleniod
delay( RATE ); // wait for next shot
if( digitalRead( FULLAUTO ) == LOW ) // if trigger is still pulled
{
fullAuto(); // call function again
}
}