Arduino 595 simulator/RT manager

// 595 Real Time Manager/Simulator
// by Ido Gendel, 2014
// Share and enjoy!

// Don't forget to set the Arduino Serial Monitor
// Baud rate to 115,200
// Pin connection scheme is below.

#define PIN_CONTROLS 6
#define NON_PIN 255

const byte SER_PIN   = 7;
const byte SRCLK_PIN = 8;
const byte OE_PIN    = 6;
const byte RCLK_PIN  = 9;
const byte SRCLR_PIN = 10;

char cmd = 0;
byte SRCLKRecIndex;

// Pin controls
byte clocksTied  = 0;
// output simulator
byte currSER     = 0;
byte SR          = 0;
byte SRClearing  = 0;
byte Q           = 0;
byte QEnabled    = 1;
byte QHPrime     = 0;

//---------------------------------------------------------
void SERChange(char state) {
  currSER = state;
} // SERChange

//---------------------------------------------------------
void SRCLKChange(char state) {

  if (!state) return;
  SR = ((SR << 1) + currSER) * (!SRClearing);
  QHPrime = SR >> 7;

} // SRCLKChange

//---------------------------------------------------------
void RCLKChange(char state) {
  if (state) Q = SR;
  if (clocksTied) cmd = 'C';
} // RCLKChange

//---------------------------------------------------------
void OEChange(char state) {
  QEnabled = !state;
} // OEChange

//---------------------------------------------------------
void SRCLRChange(char state) {
  SRClearing = !state;
  if (SRClearing) SR = 0;
} // SRCLRChange

struct tPinCtrl {

  char enabled, id, arduinoPin, state;
  void (*fnPtr) (char);
  char name[11];

} pinCtrl[PIN_CONTROLS] =
     {{1, 'S', SER_PIN, currSER, SERChange, "SER"},
      {1, 'C', SRCLK_PIN, 0, SRCLKChange, "SRCLK"},
      {1, 'R', RCLK_PIN, 0, RCLKChange, "RCLK"},
      {1, 'E', OE_PIN, !QEnabled, OEChange, "OE"},
      {1, 'L', SRCLR_PIN, !SRClearing, SRCLRChange, "SRCLR"},
      {1, 'T', NON_PIN, 0, ClockTieChange, "Tie Clocks"}};

//---------------------------------------------------------
void ClockTieChange(char state) {
  clocksTied = state;
  pinCtrl[SRCLKRecIndex].enabled = !clocksTied;
} // ClockTieChange

//---------------------------------------------------------
// Locate correct record to avoid "magic numbers"
void findSRCLKRecIndex() {

  for (SRCLKRecIndex = 0;
        SRCLKRecIndex < PIN_CONTROLS; SRCLKRecIndex++)
   if (pinCtrl[SRCLKRecIndex].arduinoPin == SRCLK_PIN) break;

} // findSRCLKRecIndex

//---------------------------------------------------------
void setup() {

  for (byte j = 0; j < PIN_CONTROLS; j++)
   if (pinCtrl[j].arduinoPin != NON_PIN) {
     pinMode(pinCtrl[j].arduinoPin, OUTPUT);
     digitalWrite(pinCtrl[j].arduinoPin, pinCtrl[j].state);
   } // if

  findSRCLKRecIndex();
  Serial.begin(115200);

} // setup

//---------------------------------------------------------
void printFormattedByte(byte b) {

  for (byte j = 0; j < 8; j++) {
    Serial.print(b & 128 ? "1" : "0");
    b <<= 1;
  } // for

} // printFormattedByte

//---------------------------------------------------------
void printICState() {

  Serial.print(F("Shift Register (Hidden) = "));
  printFormattedByte(SR);
  Serial.println();
  Serial.print(F("Storage Register (Output) = "));
  printFormattedByte(Q);
  Serial.println(QEnabled ? " (Enabled)" : " High Z (Disabled)");
  Serial.print(F("QH' (Daisy chain output) = "));
  Serial.println((byte)QHPrime);

} // printICState

//---------------------------------------------------------
void printOptions() {

  for (byte j = 0; j < PIN_CONTROLS; j++) {

    if (!pinCtrl[j].enabled) continue;
    Serial.print("[");
    Serial.print(pinCtrl[j].id);
    Serial.print("] ");
    Serial.print(pinCtrl[j].name);
    Serial.print(F(" (current state="));
    Serial.print((byte)pinCtrl[j].state);
    Serial.println(")");

  }  // for

} // printOptions

//---------------------------------------------------------
void printHeader() {

  Serial.println();
  Serial.println(F("=================================="));
  Serial.println(F("Current 595 IC state:"));
  printICState();
  Serial.println(F("--------------------------------\n"));
  Serial.println(F("Select a pin/option to toggle:"));

} // printHeader

//---------------------------------------------------------
void loop() {

  char c, userInput = 0;
  byte j;

 printHeader();
 printOptions();

 while (!cmd)
  if (Serial.available()) {
     cmd = toupper(Serial.read());
     userInput = 1;
  } // if

  c = cmd;
  cmd = 0;

  for (j = 0; j < PIN_CONTROLS; j++)
   if (c == pinCtrl[j].id) {

     if ((!pinCtrl[j].enabled) && userInput) continue;
     pinCtrl[j].state = !pinCtrl[j].state;
     if (pinCtrl[j].arduinoPin != NON_PIN)
       digitalWrite(pinCtrl[j].arduinoPin, pinCtrl[j].state);
     pinCtrl[j].fnPtr(pinCtrl[j].state);
     break;

   } // if

  if (j ==  PIN_CONTROLS) {
    Serial.println(F("\nSorry, I don't understand!"));
    delay(1000);
  }  // if

} // loop