595ForInput.ino

/*
   I'm abusing four shift registers [in chains of two each] to get 32 inputs
*/
#define NUMREGS 1
#define PINSPERCHAIN 8 // used to write all 1's in loop()

const int interrupt[NUMREGS] = {2}; // the two interrupt pins on the arduino uno

const int latch[NUMREGS] = {5}; // the latch pins for our shiftreg chains

const int data[NUMREGS] = {7}; // the data pins for our shiftreg chains

const int clk[NUMREGS] = {11}; // the clock pins for our shiftreg chains

String processOutput(boolean hello[NUMREGS][PINSPERCHAIN]);

volatile boolean foo[1][8] = { // array to store the returned values from each bit
  {false, false, false, false, false, false, false, false}
};

void setup() {
  // put your setup code here, to run once:
  attachInterrupt(digitalPinToInterrupt(interrupt[0]), checkInput, RISING);
  Serial.begin(9600);
  Serial.print("Test String\n");
  for (int i = 0; i < NUMREGS; i++) {
    pinMode(latch[i], OUTPUT);
    pinMode(data[i], OUTPUT);
    pinMode(clk[i], OUTPUT);
  }


}

void loop() {
  // put your main code here, to run repeatedly:
  
  for (int i = 0; i < NUMREGS; i++) {
    digitalWrite(latch[i], LOW);
    shiftOut(data[i], clk[i], LSBFIRST, 2 ^ PINSPERCHAIN - 1);
    digitalWrite(latch[i], HIGH);
  }
  
}

void checkInput() {
  // when the interrupt fires:
  for (int i = 0; i < NUMREGS; i++) { // loop through each register chain's pins and write zeroes

    for (int j = 0; j < PINSPERCHAIN; j++) {
      writeABit(0, data[i], latch[i], clk[i]);
    }
  }

  for (int i = 0; i < NUMREGS; i++) {
    // first, write a single 1 to the first register output
    writeABit(1, data[i], latch[i], clk[i]);

    // now, check the interrupt pin. It should be low, since we wrote all zeroes. however, if button 0 is pressed, the interrupt pin will be high
    // [as we wrote a single 1 to the 0th pin.] We store the check in our boolean array. Next, slowly, painfully, shift the bit we wrote high in-
    // wards one by one and check if the interrupt pin is high [i.e.] the button is pressed.

    for (int j = 0; j < PINSPERCHAIN; j++) {
      int temp = digitalRead(interrupt[i]);
      foo[i][j] = temp == 1 ? true : false;
      if (j < PINSPERCHAIN - 1) {
        writeABit(0, data[i], latch[i], clk[i]);
      }
    }
  }
  delay(10);
  Serial.println(processOutput(foo));
}

void writeABit(int b, int ds, int lat, int clk) {

  /* digitalWrite(lat, LOW); // hold the latch low while we write data
    digitalWrite(clk, HIGH); // the register accepts data while clk is high

    digitalWrite(ds, (b == 1 ? 1: 0)); // write the bit

    digitalWrite(lat, HIGH); // pull the latch high to send data
    digitalWrite(clk, LOW); // the register stops receiving data

  */

  digitalWrite(lat, LOW);
  digitalWrite(clk, HIGH);
  digitalWrite(ds, (b == 1 ? 1 : 0));
  digitalWrite(lat, HIGH);
  digitalWrite(clk, LOW);

}

String processOutput (boolean hello[NUMREGS][PINSPERCHAIN]) {
  String foo = "";
  for (int i = 0; i < NUMREGS; i++) {
    for (int j = 0; j < PINSPERCHAIN; j++) {
      boolean tpry = hello[i][j];
      if (tpry) {
        foo += "1";
      }
      else {
        foo += "0";
      }
    }
    foo += "\n";
  }
  return foo;
}