// Simple Hard Sector Floppy Emulator
// TAS 02/21/21
// for Adafruit Metro Mini
// 4ms (4000us) index pulse width - matches 5.25" 10 sector floppy
// sector delay in two parts to guarantee delay < 16383us
// loop overhead estimated at 125us, verified empirically
// constants won't change. They're used here to set pin numbers:
const int SS_ix_in = 4;    
const int HS_ix_out = 5; 
const int idx_width = 4000;
const int loop_oh = 125;
const int sec_delay = 20000 - loop_oh - idx_width - 10000;
const int idx_delay = (20000 - loop_oh - 2*idx_width)/2;

// Variables will change:
bool index_state = HIGH;
int rotary = 0;

void setup() {
  Serial.begin(9600);
  Serial.println("Arduino HSFE");
  
  pinMode(SS_ix_in, INPUT_PULLUP);
  
  pinMode(HS_ix_out, OUTPUT);

  digitalWrite(HS_ix_out, HIGH);
}

void loop() {
    wait_for_index();
    index_pulse();
    delayMicroseconds(idx_delay);
    index_pulse();
    delayMicroseconds(idx_delay);
    for (int i = 0; i < 8; i ++) {
      index_pulse();
      delayMicroseconds(10000);
      delayMicroseconds(sec_delay);
    }
// no programmed delay after last sector pulse this rotation
// program will wait for next index pulse
  index_pulse();
}

void wait_for_index() {
  index_state=HIGH;
  while (index_state == HIGH) {
   index_state=digitalRead(SS_ix_in);
   }
  }

 void index_pulse() {

  digitalWrite(HS_ix_out,LOW);  
  delayMicroseconds(idx_width);
  digitalWrite(HS_ix_out, HIGH);
  }