// AVR High-voltage Serial Fuse Reprogrammer with 12 Volt Charge Pump
// Adapted from code and design by Paul Willoughby 03/20/2010
//   http://www.rickety.us/2010/03/arduino-avr-high-voltage-serial-programmer/
//
// Fuse Calc:
//   http://www.engbedded.com/fusecalc/

// copied from https://sites.google.com/site/wayneholder/attiny-fuse-reset-with-12-volt-charge-pump?authuser=0

#include <TimerOne.h>

#define  SCI            12      // Target Clock Input
#define  SDO            11      // Target Data Output
#define  SII            10      // Target Instruction Input
#define  SDI             9      // Target Data Input
#define  VCC             8      // Target VCC
#define  HFUSE      0x747C
#define  LFUSE      0x646C
#define  EFUSE      0x666E

// Define ATTiny series signatures
#define  ATTINY13   0x9007  // L: 0x6A, H: 0xFF             8 pin
#define  ATTINY24   0x910B  // L: 0x62, H: 0xDF, E: 0xFF   14 pin
#define  ATTINY25   0x9108  // L: 0x62, H: 0xDF, E: 0xFF    8 pin
#define  ATTINY44   0x9207  // L: 0x62, H: 0xDF, E: 0xFF   14 pin
#define  ATTINY45   0x9206  // L: 0x62, H: 0xDF, E: 0xFF    8 pin
#define  ATTINY84   0x930C  // L: 0x62, H: 0xDF, E: 0xFF   14 pin
#define  ATTINY85   0x930B  // L: 0x62, H: 0xDF, E: 0xFF    8 pin

// Define Direct I/O pins for Charge Pump
#define  P1           0x04  // Pin D2
#define  P2           0x08  // Pin D3
#define  PWR          0x10  // Pin D4
#define  GND          0x20  // Pin D5
#define  REF          404   // 12 volt reference

// Variables used by Charge pump
volatile char phase = 0;
volatile char onOff = 0;
volatile char pwrOn = 0;

void ticker () {
  if (onOff) {
    DDRD = P1 | P2 | PWR | GND;
    int volts = analogRead(A0);
    if (volts < REF) {
      if (phase) {
        PORTD = P1 | PWR;
      } else {
        PORTD = P2 | PWR;
      }
      phase ^= 1;
    } else {
      pwrOn = 1;
    }
  } else {
    pwrOn = 0;
    DDRD = GND;
    PORTD = GND;
  }
}

void setup() {
  pinMode(VCC, OUTPUT);
  pinMode(SDI, OUTPUT);
  pinMode(SII, OUTPUT);
  pinMode(SCI, OUTPUT);
  pinMode(SDO, OUTPUT);          // Configured as input when in programming mode
  Serial.begin(57600);

  analogReference(DEFAULT);      // Setup timer interrupt for charge pump
  Timer1.initialize(500);
  Timer1.attachInterrupt(ticker);
}

void loop() {
   if (Serial.available() > 0) {
    Serial.read();
    pinMode(SDO, OUTPUT);     // Set SDO to output
    digitalWrite(SDI, LOW);
    digitalWrite(SII, LOW);
    digitalWrite(SDO, LOW);
    onOff = 0;                // 12v Off
    digitalWrite(VCC, HIGH);  // Vcc On
    delayMicroseconds(20);
    onOff = 1;                // 12v On
    while (pwrOn == 0)
      ;
    delayMicroseconds(10);
    pinMode(SDO, INPUT);      // Set SDO to input
    delayMicroseconds(300);
    unsigned int sig = readSignature();
    Serial.print("Signature is: ");
    Serial.println(sig, HEX);
    readFuses();
    if (sig == ATTINY13) {
      writeFuse(LFUSE, 0x6A);
      writeFuse(HFUSE, 0xFF);
    } else if (sig == ATTINY24 || sig == ATTINY44 || sig == ATTINY84 ||
               sig == ATTINY25 || sig == ATTINY45 || sig == ATTINY85) {
      writeFuse(LFUSE, 0x62);
      writeFuse(HFUSE, 0xDF);
      writeFuse(EFUSE, 0xFF);
    }
    readFuses();
    digitalWrite(SCI, LOW);
    digitalWrite(VCC, LOW);    // Vcc Off
    onOff = 0;                 // 12v Off
  }
}

byte shiftOut (byte val1, byte val2) {
  int inBits = 0;

  while (!digitalRead(SDO))               // Wait until SDO goes high
    ;
  unsigned int dout = (unsigned int) val1 << 2;
  unsigned int iout = (unsigned int) val2 << 2;

  for (int ii = 10; ii >= 0; ii--)  {
    digitalWrite(SDI, !!(dout & (1 << ii)));
    digitalWrite(SII, !!(iout & (1 << ii)));

    inBits <<= 1;
    inBits |= digitalRead(SDO);

    digitalWrite(SCI, HIGH);
    digitalWrite(SCI, LOW);
  }
  return inBits >> 2;
}

void writeFuse (unsigned int fuse, byte val) {
  shiftOut(0x40, 0x4C);
  shiftOut( val, 0x2C);
  shiftOut(0x00, (byte) (fuse >> 8));
  shiftOut(0x00, (byte) fuse);
}

void readFuses () {
  byte val;
        shiftOut(0x04, 0x4C);   // LFuse
        shiftOut(0x00, 0x68);
  val = shiftOut(0x00, 0x6C);
  Serial.print("LFuse: "  );    Serial.print(val, HEX);

        shiftOut(0x04, 0x4C);   // HFuse
        shiftOut(0x00, 0x7A);
  val = shiftOut(0x00, 0x7E);
  Serial.print(", HFuse: ");    Serial.print(val, HEX);

        shiftOut(0x04, 0x4C);   // EFuse
        shiftOut(0x00, 0x6A);
  val = shiftOut(0x00, 0x6E);
  Serial.print(", EFuse: ");    Serial.println(val, HEX);
}

unsigned int readSignature () {
  unsigned int sig = 0;
  byte val;
  for (int ii = 1; ii < 3; ii++) {
          shiftOut(0x08, 0x4C);
          shiftOut(  ii, 0x0C);
          shiftOut(0x00, 0x68);
    val = shiftOut(0x00, 0x6C);
    sig = (sig << 8) + val;
  }
  return sig;
}