First draft of better MAX44009 detection

sonoff/xsns_91_max44009.ino

@@ -29,34 +29,47 @@
 
 #define MAX44009_ADDR1         0x4A
 #define MAX44009_ADDR2         0x4B
+#define MAX44009_NO_REGISTERS  8
 #define REG_CONFIG 0x02
 #define REG_LUMINANCE 0x03
 #define MAX44009_CONTINUOUS_AUTO_MODE 0x80 // Start measurement in automatic, continous mode
 
 uint8_t max44009_address;
-uint8_t max44009_addresses[] = { MAX44009_ADDR1, MAX44009_ADDR2 };
-uint8_t max44009_type = 0;
+uint8_t max44009_addresses[] = { MAX44009_ADDR1, MAX44009_ADDR2, 0 }; //0 terminated list
+uint8_t max44009_found = 0;
 uint8_t max44009_valid = 0;
 float max44009_illuminance = 0;   
 char max44009_types[] = "MAX44009";
 
 bool Max4409Read_lum(void)
 {
-  if (max44009_valid) { max44009_valid--; }
-
+  max44009_valid = 0;
   /* Select luminance start register */
   Wire.beginTransmission(max44009_address);
   Wire.write(REG_LUMINANCE);
   Wire.endTransmission();
 
-  if (2 != Wire.requestFrom(max44009_address, (uint8_t)2)) { return false; }
+  if (2 != Wire.requestFrom(max44009_address, (uint8_t)2)) { 
+    return false; 
+  }
   byte msb = Wire.read();
   byte lsb = Wire.read();
   int exponent = (msb & 0xF0) >> 4;
   int mantissa = ((msb & 0x0F) << 4) | (lsb & 0x0F);
   max44009_illuminance = pow(2, exponent) * mantissa * 0.045;
   
-  max44009_valid = SENSOR_MAX_MISS;
+  max44009_valid = 1;
+  return true;
+}
+
+bool Max4409Read_register(uint8_t regno, byte *value) {
+  Wire.beginTransmission(max44009_address);
+  Wire.write(regno);
+  if ((0 != Wire.endTransmission()) ||
+      (1 != Wire.requestFrom(max44009_address, (uint8_t)1))) { 
+    return false; 
+  } 
+  *value = (byte)Wire.read();
   return true;
 }
 
@@ -64,23 +77,63 @@ bool Max4409Read_lum(void)
 
 void Max4409Detect(void)
 {
-  if (max44009_type) {
+  byte reg[8];
+  bool failed = false;
+
+  if (max44009_found) {
     return;
   }
 
-  for (byte i = 0; i < sizeof(max44009_addresses); i++) {
+  for (byte i = 0; 0 != max44009_addresses[i]; i++) {
     max44009_address = max44009_addresses[i];
-    Wire.beginTransmission(max44009_address);
 
-    /* select configuration register iand set mode */
-    Wire.write(REG_CONFIG);
-    Wire.write(MAX44009_CONTINUOUS_AUTO_MODE);
-    if (!Wire.endTransmission()) {
-      max44009_type = 1;
-      snprintf_P(log_data, sizeof(log_data), S_LOG_I2C_FOUND_AT, max44009_types, max44009_address);
+    // we need to read each register separately, as auto-increment is only 
+    // supported for illiminance registers
+    for (byte r = 0; r < MAX44009_NO_REGISTERS; r++) {
+      if (false == Max4409Read_register(r, &reg[r])) {
+        snprintf_P(log_data, sizeof(log_data), "MAX44009 at %x: Failed to read register %d",
+                   max44009_address, (int)r);
+        AddLog(LOG_LEVEL_DEBUG);
+        failed = true;
+        break;
+      }
+    }
+    if (failed) {
+      continue;
+    }
+      
+    snprintf_P(log_data, sizeof(log_data), "MAX44009 at %x: Read %x %x %x %x %x %x %x %x",
+	    (int) max44009_address, (int)reg[0], (int)reg[1], (int)reg[2], (int)reg[3], 
+            (int)reg[4], (int)reg[5], (int)reg[6], (int)reg[7]);
+    AddLog(LOG_LEVEL_DEBUG);
+
+    if ( (0x00 == reg[0]) &&
+         (0x00 == reg[1]) &&
+         ( (0x00 == (reg[2] & 0xc0)) || (MAX44009_CONTINUOUS_AUTO_MODE == (reg[2] & 0xc0)) ) &&
+         (0xef == reg[5]) &&
+         (0x00 == reg[6]) &&
+         (0xff == reg[7])) {
+
+      // looks reasonable, try to initialize 
+
+      Wire.beginTransmission(max44009_address);
+
+      // select configuration register and set mode 
+      Wire.write(REG_CONFIG);
+      Wire.write(MAX44009_CONTINUOUS_AUTO_MODE);
+      if (0 == Wire.endTransmission()) {
+        max44009_found = 1;
+        snprintf_P(log_data, sizeof(log_data), S_LOG_I2C_FOUND_AT, max44009_types, max44009_address);
+        AddLog(LOG_LEVEL_DEBUG);
+        break;
+      }  else {
+        snprintf_P(log_data, sizeof(log_data), "MAX44009 at %x: config failed!", max44009_address);
+        AddLog(LOG_LEVEL_DEBUG);
+      }
+    } else {
+      snprintf_P(log_data, sizeof(log_data), "Reading initial data failed: No MAX44009 at %x", max44009_address);
       AddLog(LOG_LEVEL_DEBUG);
-      break;
-    } 
+    }
   }
 }
 
@@ -92,11 +145,8 @@ void Max4409EverySecond(void)
   }
   else {
     // 1mS
-    if (max44009_type) {
-      if (!Max4409Read_lum()) {
-        AddLogMissed(max44009_types, max44009_valid);
-//        if (!max44009_valid) { max44009_type = 0; }
-      }
+    if (max44009_found) {
+      Max4409Read_lum();
     }
   }
 }
@@ -143,9 +193,9 @@ boolean Xsns91(byte function)
 
   if (i2c_flg) {
     switch (function) {
-      case FUNC_INIT:
-        Max4409Detect();
-        break;
+//      case FUNC_INIT:
+//        Max4409Detect();
+//        break;
       case FUNC_EVERY_SECOND:
         Max4409EverySecond();
         break;