Merge pull request #49 from sellensr/master

begin() fail gracefully

Author: hoffmannjan

Adafruit_BME280.cpp

@@ -117,9 +117,15 @@ bool Adafruit_BME280::begin(uint8_t addr, TwoWire *theWire)
 /**************************************************************************/
 bool Adafruit_BME280::begin(void)
 {
+    bool status = false;
     _i2caddr = BME280_ADDRESS;
 	_wire = &Wire;
-	return init();
+	status = init();
+ 	if(!status){
+ 		_i2caddr = BME280_ADDRESS_ALTERNATE;
+ 		status = init();
+ 		}
+	return status;
 }
 
 /**************************************************************************/
@@ -149,7 +155,8 @@ bool Adafruit_BME280::init()
     }
 
     // check if sensor, i.e. the chip ID is correct
-    if (read8(BME280_REGISTER_CHIPID) != 0x60)
+    _sensorID = read8(BME280_REGISTER_CHIPID);
+    if (_sensorID != 0x60)
         return false;
 
     // reset the device using soft-reset
@@ -613,3 +620,14 @@ float Adafruit_BME280::seaLevelForAltitude(float altitude, float atmospheric)
 
     return atmospheric / pow(1.0 - (altitude/44330.0), 5.255);
 }
+		
+/**************************************************************************/
+/*!
+    Returns Sensor ID found by init() for diagnostics 
+    @returns Sensor ID 0x60 for BME280, 0x56, 0x57, 0x58 BMP280
+*/
+/**************************************************************************/
+uint32_t Adafruit_BME280::sensorID(void)
+{
+	return _sensorID;
+}

Adafruit_BME280.h

@@ -35,7 +35,13 @@
     @brief  default I2C address
 */
 /**************************************************************************/
-    #define BME280_ADDRESS                (0x77)
+    #define BME280_ADDRESS                (0x77)	// Primary I2C Address
+/**************************************************************************/
+/*! 
+    @brief  alternate I2C address
+*/
+/**************************************************************************/
+    #define BME280_ADDRESS_ALTERNATE      (0x76)	// Alternate Address
 /*=========================================================================*/
 
 /**************************************************************************/
@@ -219,7 +225,7 @@ class Adafruit_BME280 {
 
         float readAltitude(float seaLevel);
         float seaLevelForAltitude(float altitude, float pressure);
-
+		uint32_t sensorID(void);
 
     protected:
 		TwoWire *_wire; //!< pointer to a TwoWire object

examples/bme280test/bme280test.ino

@@ -36,15 +36,21 @@ unsigned long delayTime;
 
 void setup() {
     Serial.begin(9600);
+    while(!Serial);    // time to get serial running
     Serial.println(F("BME280 test"));
 
-    bool status;
+    unsigned status;
 
     // default settings
     // (you can also pass in a Wire library object like &Wire2)
     status = bme.begin();  
     if (!status) {
-        Serial.println("Could not find a valid BME280 sensor, check wiring!");
+        Serial.println("Could not find a valid BME280 sensor, check wiring, address, sensor ID!");
+        Serial.print("SensorID was: 0x"); Serial.println(bme.sensorID(),16);
+        Serial.print("        ID of 0xFF probably means a bad address, a BMP 180 or BMP 085\n");
+        Serial.print("   ID of 0x56-0x58 represents a BMP 280,\n");
+        Serial.print("        ID of 0x60 represents a BME 280.\n");
+        Serial.print("        ID of 0x61 represents a BME 680.\n");
         while (1);
     }