Simple single axis light source direction tracker

Here is the code:

// ldrCtrl.js
// 2001-12-12 - 1st cut: cludged code... :\
// this: digital control loop... tracking speed constant, delta != 0
// next: -- reverse logic driver from sensing to tracking
//       -- analog control loop... tracking speed proportianl to delta

// --------- general ---------

var c = 0; // console

// --------- light sensing code / LDR ---------

var lsPs =
  [ A3  // 0
  , A4  // 1
  ]
  , lsDr = [ "ns", "-N", "-S" ] // direction
  , cw = 6
  , iId
  , sampleCnt = 5  // times
  , sampleTme = 100 // [ms]
  , sampleBrk = 300 // [ms]
  , tstIntTme = sampleCnt*sampleTme + sampleBrk // [ms]
  , ctlIntTme = tstIntTme * 2 // [ms]
  , ctlSteps  = 5
  , delta = 10 // [mV] on 330[mV] w/ office lamp 18" away
  , lsState = 0
  ;

function test(vals,cnt,res) {
  var idx = lsPs.length;
  if (vals === undefined) {
    vals = [];
    while (--idx>=0) vals.push(0);
    idx = lsPs.length; cnt = sampleCnt;
  }
  while (--idx>=0) vals[idx]+=analogRead(lsPs[idx]);
  if (--cnt>0) {
    setTimeout(()=>test(vals,cnt),sampleTme)­;
  } else {
    idx = vals.length;
    while (--idx>=0) {
       vals[idx] = Math.round(vals[idx]/sampleCnt*3.3*1000)­;
    }
    // vals.push(Math.round((vals[0]+vals[1])/2­));
    vals.splice(0,0,Math.round((vals[0]+vals­[1])/2));
    idx = vals.length; 
    if (c) {
      res = [];
      while (--idx>=0) res.push(fmt(vals[idx],cw)+lsDr[idx]);
      console.log(res.join(""));
    }
    if (Math.abs(vals[0]-vals[1]) < delta) {
      lsState = 0; LED1.set(); LED2.set();
      setTimeout(()=>{ LED1.reset(); LED2.reset(); },20);
    } else {
      if (vals[0] < vals[1]) {
        lsState = -1; LED1.set(); LED2.set();
        setTimeout(()=>{ LED2.reset(); },20);
      } else {
        lsState = +1; LED1.set(); LED2.set();
        setTimeout(()=>{ LED1.reset(); },20);
      }
    }
    if (trOn) track();
  }
}

function lsR() { lsH(); iId = setInterval(test,tstIntTme); }
function lsH() { if (iId) iId = clearInterval(iId); }

function lsIni() {
  // setBusyIndicator(LED1);
  idx = lsPs.length;
  while (--idx>=0) pinMode(lsPs[idx],"analog");
}

// --------- stepper code ---------

// stRn  stepper status: is running
// stPs  stepper pins
// stBW  steps Backwards bit ON/OFF pattern
// stFW  steps Forward   bit ON/OFF pattern
// stSt  step bit Stop / OFF pattern
// stT   step Time in milliseconds [ms]
// stI   step Interval (from setInterval() and for clearInterval()
// sts   steps 0001,0011,0010,... pin ON/OFF pattern in use
// st    step 0..7 current step
// stDmy ...because of lint / (cond) ? exprT : exprF needs something to assign to
var stRn = false;
var stPs = [B4,B5,B6,B7];
var stFW = [0b1000,0b1100,0b0100,0b0110,0b0010,0b00­11,0b0001,0b1001];
var stBW = [0b1001,0b0001,0b0011,0b0010,0b0110,0b01­00,0b1100,0b1000];
var stSt =  0b0000;
var stCk = ()=>0;
var st  = 0;
var stT = 0;
var stI = null;
var sts = null;
var st  = 0;
var stDmy;

// setI setInterval(i,stsC) i in [ms] with (optionl) step Change (if not null), 
// and direction info (string)
var setI = function(t,stsN,d) {
  if (c) console.log("t = ",t, d); 
  if (stI) clearInterval(stI);
  if (stsN) sts = stsN;
  stRn = true;
  stI = setInterval(stp,t);
};
// stp step
var stp = function() { digitalWrite(stPs, sts[st = ++st % 8]); stCk(); };
// _sFW step ForWard
var _sFW = function(t) {
  if (c) console.log("FW w/ " + t);
  if (stT > 0) { setI((stT = t),null," ~F");
  } else { if (stT) { st = Math.abs(st - 7); } if (!stI) { st--; } setI((stT = t),stFW," FW"); }
};
// _sBW step BackWards
var _sBW = function(t) {
  if (c) console.log("BW w/ " + t);
  if (stT < 0) { setI(-(stT = t),null," ~B"); 
  } else { if (stT) { st = Math.abs(st - 7); } if (!stI) { st--; } setI(-(stT = t),stBW," BW"); }
};

// stH stepper halt function
var stH = function() {
  if (c) console.log("stepper halt");
  if (stI) { stI = clearInterval(stI); stI = null; }
  if (c) console.log(stI);
  stRn = false;
  digitalWrite(stPs, stSt);
};

// stR stepper run function - t is stepping interval in [ms]
var stR = function(t,ck) {  
  if (typeof t === "undefined" ) {
    if (stT) {
      if (c) console.log((stT > 0) ? "F>B" : "B>F");
      stR(-stT,ck);
    } else {
      if (c) console.log("What ?");
    }
  } else {
    stCk = (ck) ? ck : ()=>0;
    stDmy = (t) ? (t>0) ? _sFW(t) : _sBW(t) : stH(); 
  }
};

// --------- track code ---------

var trLsState = 0 // previous lsState
  , trOn = false  // tracking on
  , trStTme =  4  // [ms] track step time
  ;

// track function
function track() { if (lsState != trLsState) {
  stH();
  if (lsState != 0) stR((lsState<0) ? +trStTme : - trStTme
    , ()=> {
        if (Math.abs(Math.round((analogRead(lsPs[0]­)-analogRead(lsPs[1]))
          *3.3*1000))<delta) stH(); trLsState = 0;
           });
  trLsState = lsState;
} }

// track run function
function trR() { trOn = true; }

// track halt function
function trH() { stH(); trOn = false; }

// --------- general ----------

// format (integer) value v(+|-) to ds(<=7|8) digits
function fmt(v,ds) {
  var s = "      "+v, l = s.length;
  return s.substr(l-ds);
}

function onInit() {
  lsIni(); // light sensing LDR analog pin init
  lsR();   // light sensing run
  trR();   // tracking run
}

setTimeout(onInit,999); // remove before upload for save()