Large overhaul. Add get/set for mode. Add set for oversample. Add ref pressure. Add generic i2c port.

setMode() can now be used to enter one of three modes (sleep, normal, force). Current mode can be read with getMode(). setPressureOversample(), etc used to set oversample rate for pressure, humidity, temp. User can now pass in wire port (eg Wire1, softWire, etc) to beginI2C(). Reference pressure can now be setReferencePressure() for more accurate local altitude.

Author: nseidle

examples/Example1_BasicReadings/Example1_BasicReadings.ino

@@ -0,0 +1,59 @@
+/*
+  Get basic environmental readings from the BME280
+  By: Nathan Seidle
+  SparkFun Electronics
+  Date: March 9th, 2018
+  License: This code is public domain but you buy me a beer if you use this and we meet someday (Beerware license).
+
+  https://github.com/sparkfun/SparkFun_BME280_Arduino_Library
+
+  This example shows how to obtain humidity, pressure, and current temperature from the BME280. It
+  assumes an I2C connection.
+
+  Resources:
+  Uses Wire.h for I2C operation
+  Uses SPI.h for SPI operation
+
+  Development environment specifics:
+  Arduino IDE 1.8.5
+
+*/
+
+#include "Wire.h"
+
+#include "SparkFunBME280.h"
+BME280 mySensor; //Global sensor object
+
+void setup()
+{
+  Serial.begin(9600);
+  while(!Serial); //Wait for terminal to open
+  Serial.println("Reading basic values from BME280");
+
+  if (mySensor.beginI2C() == false) //Begin communication over I2C
+  {
+    Serial.println("The chip did not respond. Please check wiring.");
+    while(1); //Freeze
+  }
+}
+
+void loop()
+{
+  Serial.print("Humidity: ");
+  Serial.print(mySensor.readFloatHumidity(), 0);
+
+  Serial.print(" Pressure: ");
+  Serial.print(mySensor.readFloatPressure(), 0);
+
+  Serial.print(" Alt: ");
+  //Serial.print(mySensor.readFloatAltitudeMeters(), 1);
+  Serial.print(mySensor.readFloatAltitudeFeet(), 1);
+
+  Serial.print(" Temp: ");
+  //Serial.print(mySensor.readTempC(), 2);
+  Serial.print(mySensor.readTempF(), 2);
+
+  Serial.println();
+
+  delay(50);
+}

src/SparkFunBME280.cpp

@@ -40,15 +40,14 @@ BME280::BME280( void )
 
 	//Select interface mode
 	settings.commInterface = I2C_MODE; //Can be I2C_MODE, SPI_MODE
+
 	//Select address for I2C.  Does nothing for SPI
 	settings.I2CAddress = 0x77; //Ignored for SPI_MODE
+
 	//Select CS pin for SPI.  Does nothing for I2C
 	settings.chipSelectPin = 10;
-	settings.runMode = 0;
-	settings.tempOverSample = 0;
-	settings.pressOverSample = 0;
-	settings.humidOverSample = 0;
 
+	settings.runMode = 0;
 }
 
 
@@ -63,13 +62,14 @@ BME280::BME280( void )
 //****************************************************************************//
 uint8_t BME280::begin()
 {
+	delay(2);  //Make sure sensor had enough time to turn on. BME280 requires 2ms to start up.
+
 	//Check the settings structure values to determine how to setup the device
-	uint8_t dataToWrite = 0;  //Temporary variable
 	switch (settings.commInterface)
 	{
 
 	case I2C_MODE:
-		Wire.begin();
+		if(_i2cPort != 0) _i2cPort->begin();
 		break;
 
 	case SPI_MODE:
@@ -125,30 +125,141 @@ uint8_t BME280::begin()
 	calibration.dig_H5 = ((int16_t)((readRegister(BME280_DIG_H5_MSB_REG) << 4) + ((readRegister(BME280_DIG_H4_LSB_REG) >> 4) & 0x0F)));
 	calibration.dig_H6 = ((int8_t)readRegister(BME280_DIG_H6_REG));
 
-	//Set the oversampling control words.
-	//config will only be writeable in sleep mode, so first insure that.
-	writeRegister(BME280_CTRL_MEAS_REG, 0x00);
+	settings.runMode = 3; //  3, Normal mode
+	settings.tStandby = 0; //  0, 0.5ms
+	settings.filter = 0; //  0, filter off
+
+	setPressureOverSample(1); //Default
+	setHumidityOverSample(1); //Default
+	setTempOverSample(1); //Default
+	
+	setMode(MODE_NORMAL); //Go!
 
-	//Set the config word
-	dataToWrite = (settings.tStandby << 0x5) & 0xE0;
-	dataToWrite |= (settings.filter << 0x02) & 0x1C;
-	writeRegister(BME280_CONFIG_REG, dataToWrite);
+	return(readRegister(BME280_CHIP_ID_REG)); //Should return 0x60
+}
+
+//Begin comm with BME280 over I2C
+bool BME280::beginI2C(TwoWire &wirePort)
+{
+	_i2cPort = &wirePort;
+	_i2cPort->begin(); //The caller can begin their port and set the speed. We just confirm it here otherwise it can be hard to debug.
 
-	//Set ctrl_hum first, then ctrl_meas to activate ctrl_hum
-	dataToWrite = settings.humidOverSample & 0x07; //all other bits can be ignored
-	writeRegister(BME280_CTRL_HUMIDITY_REG, dataToWrite);
+	settings.commInterface = I2C_MODE;
+	//settings.I2CAddress = 0x77; //We assume user has set the I2C address using setI2CAddress()
 
-	//set ctrl_meas
-	//First, set temp oversampling
-	dataToWrite = (settings.tempOverSample << 0x5) & 0xE0;
-	//Next, pressure oversampling
-	dataToWrite |= (settings.pressOverSample << 0x02) & 0x1C;
-	//Last, set mode
-	dataToWrite |= (settings.runMode) & 0x03;
-	//Load the byte
-	writeRegister(BME280_CTRL_MEAS_REG, dataToWrite);
+	if(begin() == 0x60) return(true); //Begin normal init with these settings. Should return chip ID of 0x60
+	return(false);
+}
+
+//Set the mode bits in the ctrl_meas register
+//Mode 00 = Sleep
+// 01 and 10 = Forced
+// 11 = Normal mode
+void BME280::setMode(uint8_t mode)
+{
+	if(mode > 0b11) mode = 0; //Error check. Default to sleep mode
 
-	return readRegister(0xD0);
+	uint8_t controlData = readRegister(BME280_CTRL_MEAS_REG);
+	controlData &= ~( (1<<1) | (1<<0) ); //Clear the mode[1:0] bits
+	controlData |= mode; //Set
+	writeRegister(BME280_CTRL_MEAS_REG, controlData);
+}
+
+//Gets the current mode bits in the ctrl_meas register
+//Mode 00 = Sleep
+// 01 and 10 = Forced
+// 11 = Normal mode
+uint8_t BME280::getMode()
+{
+	uint8_t controlData = readRegister(BME280_CTRL_MEAS_REG);
+	return(controlData & 0b11111100); //Mask out all but bits 1 and 0
+}
+
+//Set the temperature oversample value
+//0 turns off temp sensing
+//1 to 16 are valid over sampling values
+void BME280::setTempOverSample(uint8_t overSampleAmount)
+{
+	overSampleAmount = checkSampleValue(overSampleAmount); //Error check
+	
+	uint8_t originalMode = getMode(); //Get the current mode so we can go back to it at the end
+	
+	setMode(MODE_SLEEP); //Config will only be writeable in sleep mode, so first go to sleep mode
+
+	//Set the osrs_t bits (7, 6, 5) to overSampleAmount
+	uint8_t controlData = readRegister(BME280_CTRL_MEAS_REG);
+	controlData &= ~( (1<<7) | (1<<6) | (1<<5) ); //Clear bits 765
+	controlData |= overSampleAmount << 5; //Align overSampleAmount to bits 7/6/5
+	writeRegister(BME280_CTRL_MEAS_REG, controlData);
+	
+	setMode(originalMode); //Return to the original user's choice
+}
+
+//Set the pressure oversample value
+//0 turns off pressure sensing
+//1 to 16 are valid over sampling values
+void BME280::setPressureOverSample(uint8_t overSampleAmount)
+{
+	overSampleAmount = checkSampleValue(overSampleAmount); //Error check
+	
+	uint8_t originalMode = getMode(); //Get the current mode so we can go back to it at the end
+	
+	setMode(MODE_SLEEP); //Config will only be writeable in sleep mode, so first go to sleep mode
+
+	//Set the osrs_p bits (4, 3, 2) to overSampleAmount
+	uint8_t controlData = readRegister(BME280_CTRL_MEAS_REG);
+	controlData &= ~( (1<<4) | (1<<3) | (1<<2) ); //Clear bits 432
+	controlData |= overSampleAmount << 2; //Align overSampleAmount to bits 4/3/2
+	writeRegister(BME280_CTRL_MEAS_REG, controlData);
+	
+	setMode(originalMode); //Return to the original user's choice
+}
+
+//Set the humidity oversample value
+//0 turns off humidity sensing
+//1 to 16 are valid over sampling values
+void BME280::setHumidityOverSample(uint8_t overSampleAmount)
+{
+	overSampleAmount = checkSampleValue(overSampleAmount); //Error check
+	
+	uint8_t originalMode = getMode(); //Get the current mode so we can go back to it at the end
+	
+	setMode(MODE_SLEEP); //Config will only be writeable in sleep mode, so first go to sleep mode
+
+	//Set the osrs_h bits (2, 1, 0) to overSampleAmount
+	uint8_t controlData = readRegister(BME280_CTRL_HUMIDITY_REG);
+	controlData &= ~( (1<<2) | (1<<1) | (1<<0) ); //Clear bits 2/1/0
+	controlData |= overSampleAmount << 0; //Align overSampleAmount to bits 2/1/0
+	writeRegister(BME280_CTRL_HUMIDITY_REG, controlData);
+
+	setMode(originalMode); //Return to the original user's choice
+}
+
+//Validates an over sample value
+//Allowed values are 0 to 16
+//These are used in the humidty, pressure, and temp oversample functions
+uint8_t BME280::checkSampleValue(uint8_t userValue)
+{
+	switch(userValue) 
+	{
+		case(0): break; //Valid
+		case(1): break; //Valid
+		case(2): break; //Valid
+		case(4): break; //Valid
+		case(8): break; //Valid
+		case(16): break; //Valid
+		default: 
+			userValue = 1; //Default to 1x
+			break; //Good
+	}
+	return(userValue);	
+}
+
+//Set the global setting for the I2C address we want to communicate with
+//Default is 0x77
+void BME280::setI2CAddress(uint8_t address)
+{
+	settings.I2CAddress = address; //Set the I2C address for this device
 }
 
 //Strictly resets.  Run .begin() afterwards
@@ -191,11 +302,25 @@ float BME280::readFloatPressure( void )
 
 }
 
+//Sets the internal variable _referencePressure so the 
+void BME280::setReferencePressure(float refPressure)
+{
+	_referencePressure = rePressure;
+}
+
+//Return the local reference pressure
+float BME280::getReferencePressure()
+{
+	return(_referencePressure);
+}
+
+
+
 float BME280::readFloatAltitudeMeters( void )
 {
 	float heightOutput = 0;
 
-	heightOutput = ((float)-45846.2)*(pow(((float)readFloatPressure()/(float)101325), 0.190263) - (float)1);
+	heightOutput = ((float)-45846.2)*(pow(((float)readFloatPressure()/(float)_referencePressure), 0.190263) - (float)1);
 	return heightOutput;
 
 }
@@ -287,15 +412,15 @@ void BME280::readRegisterRegion(uint8_t *outputPointer , uint8_t offset, uint8_t
 	{
 
 	case I2C_MODE:
-		Wire.beginTransmission(settings.I2CAddress);
-		Wire.write(offset);
-		Wire.endTransmission();
+		_i2cPort->beginTransmission(settings.I2CAddress);
+		_i2cPort->write(offset);
+		_i2cPort->endTransmission();
 
 		// request bytes from slave device
-		Wire.requestFrom(settings.I2CAddress, length);
-		while ( (Wire.available()) && (i < length))  // slave may send less than requested
+		_i2cPort->requestFrom(settings.I2CAddress, length);
+		while ( (_i2cPort->available()) && (i < length))  // slave may send less than requested
 		{
-			c = Wire.read(); // receive a byte as character
+			c = _i2cPort->read(); // receive a byte as character
 			*outputPointer = c;
 			outputPointer++;
 			i++;
@@ -332,14 +457,14 @@ uint8_t BME280::readRegister(uint8_t offset)
 	switch (settings.commInterface) {
 
 	case I2C_MODE:
-		Wire.beginTransmission(settings.I2CAddress);
-		Wire.write(offset);
-		Wire.endTransmission();
+		_i2cPort->beginTransmission(settings.I2CAddress);
+		_i2cPort->write(offset);
+		_i2cPort->endTransmission();
 
-		Wire.requestFrom(settings.I2CAddress, numBytes);
-		while ( Wire.available() ) // slave may send less than requested
+		_i2cPort->requestFrom(settings.I2CAddress, numBytes);
+		while ( _i2cPort->available() ) // slave may send less than requested
 		{
-			result = Wire.read(); // receive a byte as a proper uint8_t
+			result = _i2cPort->read(); // receive a byte as a proper uint8_t
 		}
 		break;
 
@@ -375,10 +500,10 @@ void BME280::writeRegister(uint8_t offset, uint8_t dataToWrite)
 	{
 	case I2C_MODE:
 		//Write the byte
-		Wire.beginTransmission(settings.I2CAddress);
-		Wire.write(offset);
-		Wire.write(dataToWrite);
-		Wire.endTransmission();
+		_i2cPort->beginTransmission(settings.I2CAddress);
+		_i2cPort->write(offset);
+		_i2cPort->write(dataToWrite);
+		_i2cPort->endTransmission();
 		break;
 
 	case SPI_MODE: