Merge pull request #50 from cdonate/feature/data_burst_readout

feat: add read burst

Author: nseidle

examples/Example11_BurstRead/Example11_BurstRead.ino

@@ -0,0 +1,68 @@
+/*
+  Get environmental readings as a burst from the BME280
+  By: Claudio Donaté
+  Date: December 30th, 2020
+  License: This code is public domain but you buy me a beer if you use this and we meet someday (Beerware license).
+
+  Feel like supporting our work? Buy a board from SparkFun!
+  https://www.sparkfun.com/products/14348 - Qwiic Combo Board
+  https://www.sparkfun.com/products/13676 - BME280 Breakout Board
+  
+  This example shows how to read humidity, pressure, and current temperature from the BME280 over I2C reading all registers at once.
+  Please check BME280 Datasheet, section 4, Data readout for detail explanations on why.
+
+  Hardware connections:
+  BME280 -> Arduino
+  GND -> GND
+  3.3 -> 3.3
+  SDA -> A4
+  SCL -> A5
+*/
+
+#include <Wire.h>
+
+#include "SparkFunBME280.h"
+
+#define CELSIUS_SCALE 0 //Default
+#define FAHRENHEIT_SCALE 1
+
+BME280 mySensor;
+BME280_SensorMeasurements measurements;
+
+void setup()
+{
+  Serial.begin(9600);
+  Serial.println("Reading basic values from BME280 as a Burst");
+
+  Wire.begin();
+
+  if (mySensor.beginI2C() == false) //Begin communication over I2C
+  {
+    Serial.println("The sensor did not respond. Please check wiring.");
+    while(1); //Freeze
+  }
+}
+
+void loop()
+{
+  while (mySensor.isMeasuring()) // Wait for sensor to finish measuring
+  {
+      Serial.print("."); 
+  };
+    
+  mySensor.readAllMeasurements(&measurements); // Return temperature in Celsius
+  // mySensor.readAllMeasurements(&measurements, FAHRENHEIT_SCALE);
+  
+  Serial.print("\nHumidity: ");
+  Serial.print(measurements.humidity, 0);
+
+  Serial.print(" Pressure: ");
+  Serial.print(measurements.pressure, 0);
+
+  Serial.print(" Temp: ");
+  Serial.print(measurements.temperature, 2);
+
+  Serial.println();
+
+  delay(50);
+}

src/SparkFunBME280.cpp

@@ -355,6 +355,29 @@ void BME280::reset( void )
 
 }
 
+//****************************************************************************//
+//
+//  Burst Measurement Section
+//
+//****************************************************************************//
+
+//Read all sensor registers as a burst. See BME280 Datasheet section 4. Data readout
+//tempScale = 0 for Celsius scale (default setting)
+//tempScale = 1 for Fahrenheit scale
+void BME280::readAllMeasurements(BME280_SensorMeasurements *measurements, byte tempScale){
+	
+	uint8_t dataBurst[8];
+	readRegisterRegion(dataBurst, BME280_MEASUREMENTS_REG, 8);
+	
+	if(tempScale == 0){
+		readTempCFromBurst(dataBurst, measurements);
+	}else{
+		readTempFFromBurst(dataBurst, measurements);
+	}
+	readFloatPressureFromBurst(dataBurst, measurements);
+	readFloatHumidityFromBurst(dataBurst, measurements);
+}
+
 //****************************************************************************//
 //
 //  Pressure Section
@@ -390,6 +413,37 @@ float BME280::readFloatPressure( void )
 
 }
 
+void BME280::readFloatPressureFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements)
+{
+
+	// Set pressure in Pa as unsigned 32 bit integer in Q24.8 format (24 integer bits and 8 fractional bits).
+	// Output value of “24674867” represents 24674867/256 = 96386.2 Pa = 963.862 hPa
+  
+  int32_t adc_P = ((uint32_t)buffer[0] << 12) | ((uint32_t)buffer[1] << 4) | ((buffer[2] >> 4) & 0x0F);
+	
+	int64_t var1, var2, p_acc;
+	var1 = ((int64_t)t_fine) - 128000;
+	var2 = var1 * var1 * (int64_t)calibration.dig_P6;
+	var2 = var2 + ((var1 * (int64_t)calibration.dig_P5)<<17);
+	var2 = var2 + (((int64_t)calibration.dig_P4)<<35);
+	var1 = ((var1 * var1 * (int64_t)calibration.dig_P3)>>8) + ((var1 * (int64_t)calibration.dig_P2)<<12);
+	var1 = (((((int64_t)1)<<47)+var1))*((int64_t)calibration.dig_P1)>>33;
+	if (var1 == 0)
+	{
+		measurements->pressure = 0; // avoid exception caused by division by zero
+	}
+	else
+	{
+		p_acc = 1048576 - adc_P;
+		p_acc = (((p_acc<<31) - var2)*3125)/var1;
+		var1 = (((int64_t)calibration.dig_P9) * (p_acc>>13) * (p_acc>>13)) >> 25;
+		var2 = (((int64_t)calibration.dig_P8) * p_acc) >> 19;
+		p_acc = ((p_acc + var1 + var2) >> 8) + (((int64_t)calibration.dig_P7)<<4);
+		
+		measurements->pressure = (float)p_acc / 256.0;
+	}
+}
+
 // Sets the internal variable _referencePressure so the altitude is calculated properly.
 // This is also known as "sea level pressure" and is in Pascals. The value is probably
 // within 10% of 101325. This varies based on the weather:
@@ -459,6 +513,25 @@ float BME280::readFloatHumidity( void )
 	return (float)(var1>>12) / 1024.0;
 }
 
+void BME280::readFloatHumidityFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements)
+{
+	
+	// Set humidity in %RH as unsigned 32 bit integer in Q22. 10 format (22 integer and 10 fractional bits).
+	// Output value of “47445” represents 47445/1024 = 46. 333 %RH
+  int32_t adc_H = ((uint32_t)buffer[6] << 8) | ((uint32_t)buffer[7]);
+	
+	int32_t var1;
+	var1 = (t_fine - ((int32_t)76800));
+	var1 = (((((adc_H << 14) - (((int32_t)calibration.dig_H4) << 20) - (((int32_t)calibration.dig_H5) * var1)) +
+	((int32_t)16384)) >> 15) * (((((((var1 * ((int32_t)calibration.dig_H6)) >> 10) * (((var1 * ((int32_t)calibration.dig_H3)) >> 11) + ((int32_t)32768))) >> 10) + ((int32_t)2097152)) *
+	((int32_t)calibration.dig_H2) + 8192) >> 14));
+	var1 = (var1 - (((((var1 >> 15) * (var1 >> 15)) >> 7) * ((int32_t)calibration.dig_H1)) >> 4));
+	var1 = (var1 < 0 ? 0 : var1);
+	var1 = (var1 > 419430400 ? 419430400 : var1);
+
+	measurements->humidity = (float)(var1>>12) / 1024.0;
+}
+
 //****************************************************************************//
 //
 //  Temperature Section
@@ -494,6 +567,29 @@ float BME280::readTempC( void )
 	return output;
 }
 
+float BME280::readTempFromBurst(uint8_t buffer[])
+{
+  int32_t adc_T = ((uint32_t)buffer[3] << 12) | ((uint32_t)buffer[4] << 4) | ((buffer[5] >> 4) & 0x0F);
+
+	//By datasheet, calibrate
+	int64_t var1, var2;
+
+	var1 = ((((adc_T>>3) - ((int32_t)calibration.dig_T1<<1))) * ((int32_t)calibration.dig_T2)) >> 11;
+	var2 = (((((adc_T>>4) - ((int32_t)calibration.dig_T1)) * ((adc_T>>4) - ((int32_t)calibration.dig_T1))) >> 12) *
+	((int32_t)calibration.dig_T3)) >> 14;
+	t_fine = var1 + var2;
+	float output = (t_fine * 5 + 128) >> 8;
+
+	output = output / 100 + settings.tempCorrection;
+	
+ 	return output;
+}
+
+void BME280::readTempCFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements)
+{
+  measurements->temperature = readTempFromBurst(buffer);
+}
+
 float BME280::readTempF( void )
 {
 	float output = readTempC();
@@ -502,6 +598,14 @@ float BME280::readTempF( void )
 	return output;
 }
 
+void BME280::readTempFFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements)
+{
+  float output = readTempFromBurst(buffer);
+	output = (output * 9) / 5 + 32;
+
+	measurements->temperature = output;
+}
+
 //****************************************************************************//
 //
 //  Dew point Section

src/SparkFunBME280.h

@@ -105,6 +105,7 @@ Distributed as-is; no warranty is given.
 #define BME280_STAT_REG					0xF3 //Status Reg
 #define BME280_CTRL_MEAS_REG			0xF4 //Ctrl Measure Reg
 #define BME280_CONFIG_REG				0xF5 //Configuration Reg
+#define BME280_MEASUREMENTS_REG			0xF7 //Measurements register start
 #define BME280_PRESSURE_MSB_REG			0xF7 //Pressure MSB
 #define BME280_PRESSURE_LSB_REG			0xF8 //Pressure LSB
 #define BME280_PRESSURE_XLSB_REG		0xF9 //Pressure XLSB
@@ -172,6 +173,14 @@ struct SensorCalibration
 
 };
 
+struct BME280_SensorMeasurements
+{
+  public:
+	float temperature;
+	float pressure;
+	float humidity;
+};
+
 //This is the main operational class of the driver.
 
 class BME280
@@ -215,18 +224,22 @@ class BME280
 
 	//Software reset routine
 	void reset( void );
+		void readAllMeasurements(BME280_SensorMeasurements *measurements, byte tempScale = 0);
 
     //Returns the values as floats.
     float readFloatPressure( void );
 	float readFloatAltitudeMeters( void );
 	float readFloatAltitudeFeet( void );
+		void readFloatPressureFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements);
 
 	float readFloatHumidity( void );
+		void readFloatHumidityFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements);
 
     //Temperature related methods
     void setTemperatureCorrection(float corr);
     float readTempC( void );
     float readTempF( void );
+		float readTempFromBurst(uint8_t buffer[]);
 
 	//Dewpoint related methods
 	//From Pavel-Sayekat: https://github.com/sparkfun/SparkFun_BME280_Breakout_Board/pull/6/files
@@ -248,6 +261,8 @@ class BME280
 
 private:
 	uint8_t checkSampleValue(uint8_t userValue); //Checks for valid over sample values
+	void readTempCFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements);
+	void readTempFFromBurst(uint8_t buffer[], BME280_SensorMeasurements *measurements);
 
     uint8_t _wireType = HARD_WIRE; //Default to Wire.h
     TwoWire *_hardPort = NO_WIRE; //The generic connection to user's chosen I2C hardware