implement wrapper class with agc from library example code

src/tcs34725_agc.cpp

@@ -0,0 +1,85 @@
+//#include <Wire.h>
+//#include "Adafruit_TCS34725.h"
+#include "tcs34725_agc.h"
+
+//
+// Gain/time combinations to use and the min/max limits for hysteresis
+// that avoid saturation. They should be in order from dim to bright.
+//
+// Also set the first min count and the last max count to 0 to indicate
+// the start and end of the list.
+//
+const tcs34725::tcs_agc tcs34725::agc_lst[] = {
+  { TCS34725_GAIN_60X, TCS34725_INTEGRATIONTIME_700MS,     0, 20000 },
+  { TCS34725_GAIN_60X, TCS34725_INTEGRATIONTIME_154MS,  4990, 63000 },
+  { TCS34725_GAIN_16X, TCS34725_INTEGRATIONTIME_154MS, 16790, 63000 },
+  { TCS34725_GAIN_4X,  TCS34725_INTEGRATIONTIME_154MS, 15740, 63000 },
+  { TCS34725_GAIN_1X,  TCS34725_INTEGRATIONTIME_154MS, 15740, 0 }
+};
+tcs34725::tcs34725() : agc_cur(0), isAvailable(0), isSaturated(0) {
+}
+
+// initialize the sensor
+boolean tcs34725::begin(void) {
+  tcs = Adafruit_TCS34725(agc_lst[agc_cur].at, agc_lst[agc_cur].ag);
+  if ((isAvailable = tcs.begin()))
+    setGainTime();
+  return(isAvailable);
+}
+
+// Set the gain and integration time
+void tcs34725::setGainTime(void) {
+  tcs.setGain(agc_lst[agc_cur].ag);
+  tcs.setIntegrationTime(agc_lst[agc_cur].at);
+  atime = int(agc_lst[agc_cur].at);
+  atime_ms = ((256 - atime) * 2.4);
+  switch(agc_lst[agc_cur].ag) {
+  case TCS34725_GAIN_1X:
+    againx = 1;
+    break;
+  case TCS34725_GAIN_4X:
+    againx = 4;
+    break;
+  case TCS34725_GAIN_16X:
+    againx = 16;
+    break;
+  case TCS34725_GAIN_60X:
+    againx = 60;
+    break;
+  }
+}
+
+// Retrieve data from the sensor and do the calculations
+void tcs34725::getData(void) {
+  // read the sensor and autorange if necessary
+  tcs.getRawData(&r, &g, &b, &c);
+  while(1) {
+    if (agc_lst[agc_cur].maxcnt && c > agc_lst[agc_cur].maxcnt)
+      agc_cur++;
+    else if (agc_lst[agc_cur].mincnt && c < agc_lst[agc_cur].mincnt)
+      agc_cur--;
+    else break;
+
+    setGainTime();
+    delay((256 - atime) * 2.4 * 2); // shock absorber
+    tcs.getRawData(&r, &g, &b, &c);
+    break;
+  }
+
+  // DN40 calculations
+  ir = (r + g + b > c) ? (r + g + b - c) / 2 : 0;
+  r_comp = r - ir;
+  g_comp = g - ir;
+  b_comp = b - ir;
+  c_comp = c - ir;
+  cratio = float(ir) / float(c);
+
+  saturation = ((256 - atime) > 63) ? 65535 : 1024 * (256 - atime);
+  saturation75 = (atime_ms < 150) ? (saturation - saturation / 4) : saturation;
+  isSaturated = (atime_ms < 150 && c > saturation75) ? 1 : 0;
+  cpl = (atime_ms * againx) / (TCS34725_GA * TCS34725_DF);
+  maxlux = 65535 / (cpl * 3);
+
+  lux = (TCS34725_R_Coef * float(r_comp) + TCS34725_G_Coef * float(g_comp) + TCS34725_B_Coef * float(b_comp)) / cpl;
+  ct = TCS34725_CT_Coef * float(b_comp) / float(r_comp) + TCS34725_CT_Offset;
+}

src/tcs34725_agc.h

@@ -0,0 +1,48 @@
+//copied from example code: https://github.com/adafruit/Adafruit_TCS34725/blob/master/examples/tcs34725autorange/tcs34725autorange.ino
+
+#ifndef _TCS34725_AGC_H_
+#define _TCS34725_AGC_H_
+
+#include <Wire.h>
+#include "Adafruit_TCS34725.h"
+
+
+#define TCS34725_R_Coef 0.136
+#define TCS34725_G_Coef 1.000
+#define TCS34725_B_Coef -0.444
+#define TCS34725_GA 1.0
+#define TCS34725_DF 310.0
+#define TCS34725_CT_Coef 3810.0
+#define TCS34725_CT_Offset 1391.0
+
+// Autorange class for TCS34725
+class tcs34725 {
+private:
+  struct tcs_agc {
+    tcs34725Gain_t ag;
+    tcs34725IntegrationTime_t at;
+    uint16_t mincnt;
+    uint16_t maxcnt;
+  };
+  static const tcs_agc agc_lst[];
+  uint16_t agc_cur;
+
+  void setGainTime(void);
+  Adafruit_TCS34725 tcs;
+
+public:
+  tcs34725(void);
+
+  boolean begin(void);
+  void getData(void);
+
+  boolean isAvailable, isSaturated;
+  uint16_t againx, atime, atime_ms;
+  uint16_t r, g, b, c;
+  uint16_t ir;
+  uint16_t r_comp, g_comp, b_comp, c_comp;
+  uint16_t saturation, saturation75;
+  float cratio, cpl, ct, lux, maxlux;
+};
+
+#endif