Fixes readings error

CHANGES.txt

@@ -1,3 +1,8 @@
+2013-06-11
+ *  	-decoupled requests, read in, and parsing
+ *	-adjusted temperature for voltage
+ *	-stores temperature for humidity conversion rather than re-requesting it
+
 2011-09-20
  * Conditionally include Arduino.h for compatibility with Arduino 1.0
 

README.markdown

@@ -1,6 +1,9 @@
 SHT1x Temperature / Humidity Sensor Library for Arduino
 =======================================================
+Additional work done by Louis Thiery ([email protected]) - hoping to see GNU or CC copyright emerge
+
 Copyright 2009 Jonathan Oxer [email protected] / http://www.practicalarduino.com  
+
 Copyright 2008 Maurice Ribble [email protected] / http://www.glacialwanderer.com
 
 Provides a simple interface to the SHT1x series (SHT10, SHT11, SHT15)

README.markdown~

@@ -0,0 +1,64 @@
+SHT1x Temperature / Humidity Sensor Library for Arduino
+=======================================================
+Additional work done by Louis Thiery ([email protected]) - hoping to see GNU or CC copyright emerge
+Copyright 2009 Jonathan Oxer [email protected] / http://www.practicalarduino.com  
+Copyright 2008 Maurice Ribble [email protected] / http://www.glacialwanderer.com
+
+Provides a simple interface to the SHT1x series (SHT10, SHT11, SHT15)
+and SHT7x series (SHT71, SHT75) temperature / humidity sensors from
+Sensirion, http://www.sensirion.com. These sensors use a "2-wire"
+communications buss that is similar to I2C and can co-exist on the same
+physical wire as I2C devices.
+
+Installation
+------------
+Download the directory "SHT1x" and move it into the "libraries"
+directory inside your sketchbook directory, then restart the Arduino
+IDE. You will then see it listed under File->Examples->SHT1x.
+
+Usage
+-----
+The library is instantiated as an object with methods provided to read
+relative humidity and temperature. Include it in your sketch and then
+create an object, specifying the pins to use for communication with the
+sensor:
+
+    #include <SHT1x.h>
+    #define dataPin 10
+    #define clockPin 11
+    SHT1x sht1x(dataPin, clockPin);
+
+You can then call methods on that object within your program. In this
+example we created an object called "sht1x", but it could have been
+called whatever you like. A complete example program is included with
+the library and can be accessed from the File->Examples->SHT1x menu.
+
+### readTemperatureC() ###
+
+Returns a float within the valid range of the sensor of -40 to +123.8C.
+A value of -40 is returned in the event of a communication error with
+the sensor.
+
+Example:
+
+    float tempC = sht1x.readTemperatureC();
+
+### readTemperatureF() ###
+
+Returns a float within the valid range of the sensor of -40 to +254.9F.
+A value of -40 is returned in the event of a communication error with
+the sensor.
+
+Example:
+
+    float tempF = sht1x.readTemperatureF();
+
+### readHumidity() ###
+
+Returns a float within the valid range of the sensor of 0 to 100%.
+A negative value is returned in the event of a communication error with
+the sensor.
+
+Example:
+
+    float humidity = sht1x.readHumidity();

SHT1x.cpp

@@ -1,6 +1,8 @@
 /**
  * SHT1x Library
  *
+ * Recent elaborations by Louis Thiery ([email protected]) <hoping to see a GNU or CC license>
+ *
  * Copyright 2009 Jonathan Oxer <[email protected]> / <www.practicalarduino.com>
  * Based on previous work by:
  *    Maurice Ribble: <www.glacialwanderer.com/hobbyrobotics/?p=5>
@@ -17,131 +19,165 @@
 
 #include "SHT1x.h"
 
+#define DEFAULT_VOLTAGE 5
+
 SHT1x::SHT1x(int dataPin, int clockPin)
 {
   _dataPin = dataPin;
   _clockPin = clockPin;
+  _setConversionCoeffs(DEFAULT_VOLTAGE);
+}
+
+SHT1x::SHT1x(int dataPin, int clockPin, float voltage)
+{
+  _dataPin = dataPin;
+  _clockPin = clockPin;
+  _setConversionCoeffs(voltage);
+}
+
+#define VALS_IN_TABLE 5
+
+// dynamically determines conversion coefficients based on voltage
+// tables generated by datasheet
+void SHT1x::_setConversionCoeffs(float voltage){
+  _D2C =   0.01; // for 14 Bit DEGC
+  _D2F =   0.018; // for 14 Bit DEGC
+
+  const float coeffsC[] = {40.1,39.8,39.7,39.6,39.4};
+  const float coeffsF[] = {40.2,39.6,39.5,39.3,38.9};
+  const float vals[]={5,4,3.5,3,2.5};
+
+  for (int i=1;i<VALS_IN_TABLE;i++){
+	if(voltage>vals[i]){
+		_D1C=-_linearInterpolation(coeffsC[i-1],coeffsC[i],vals[i-1],voltage);
+		_D1F=-_linearInterpolation(coeffsF[i-1],coeffsF[i],vals[i-1],voltage);
+		break;
+	}
+  }
+}
+
+float SHT1x::_linearInterpolation(float coeffA, float coeffB, float valA, float input){
+        Serial.println((coeffA-coeffB)/valA*input+coeffB);
+	return (coeffA-coeffB)/valA*input+coeffB;
 }
 
 
 /* ================  Public methods ================ */
 
 /**
- * Reads the current temperature in degrees Celsius
+ * Requests, reads, and parses temperatures in C
  */
 float SHT1x::readTemperatureC()
 {
-  int _val;                // Raw value returned from sensor
-  float _temperature;      // Temperature derived from raw value
-
-  // Conversion coefficients from SHT15 datasheet
-  const float D1 = -40.0;  // for 14 Bit @ 5V
-  const float D2 =   0.01; // for 14 Bit DEGC
-
-  // Fetch raw value
-  _val = readTemperatureRaw();
-
-  // Convert raw value to degrees Celsius
-  _temperature = (_val * D2) + D1;
+  //just putting together functions
+  requestTemperature();
+  return parseTemperatureC(readInTemperature());
+}
 
-  return (_temperature);
+float SHT1x::parseTemperatureC(int raw){
+  return (raw * _D2C) + _D1C;
 }
 
+
 /**
- * Reads the current temperature in degrees Fahrenheit
+ * Requests, reads, and parses temperatures in F
  */
 float SHT1x::readTemperatureF()
 {
-  int _val;                 // Raw value returned from sensor
-  float _temperature;       // Temperature derived from raw value
+  requestTemperature();
+  return parseTemperatureF(readInTemperature());
+}
 
-  // Conversion coefficients from SHT15 datasheet
-  const float D1 = -40.0;   // for 14 Bit @ 5V
-  const float D2 =   0.018; // for 14 Bit DEGF
+float SHT1x::parseTemperatureF(int raw){
+  // Convert raw value to degrees Fahrenheit
+  return (raw * _D2F) + _D1F;
+}
 
-  // Fetch raw value
-  _val = readTemperatureRaw();
+/**
+ * Temperature Request
+ */
+void SHT1x::requestTemperature()
+{
+  int _val;
+  // Command to send to the SHT1x to request Temperature
+  int _gTempCmd  = 0b00000011;
+  sendCommandSHT(_gTempCmd, _dataPin, _clockPin);
+}
 
-  // Convert raw value to degrees Fahrenheit
-  _temperature = (_val * D2) + D1;
+/**
+ * Read-in Temperature
+ */
+int SHT1x::readInTemperature()
+{
+  waitForResultSHT(_dataPin);
 
-  return (_temperature);
+  _temperatureRaw= getData16SHT(_dataPin, _clockPin); //store in variable for humidity 
+  skipCrcSHT(_dataPin, _clockPin);
+  return _temperatureRaw;
 }
 
 /**
  * Reads current temperature-corrected relative humidity
  */
 float SHT1x::readHumidity()
 {
-  int _val;                    // Raw humidity value returned from sensor
-  float _linearHumidity;       // Humidity with linear correction applied
-  float _correctedHumidity;    // Temperature-corrected humidity
-  float _temperature;          // Raw temperature value
+  requestHumidity();
+  return parseHumidity(readInHumidity());
+}
 
-  // Conversion coefficients from SHT15 datasheet
-  const float C1 = -4.0;       // for 12 Bit
-  const float C2 =  0.0405;    // for 12 Bit
-  const float C3 = -0.0000028; // for 12 Bit
-  const float T1 =  0.01;      // for 14 Bit @ 5V
-  const float T2 =  0.00008;   // for 14 Bit @ 5V
+void SHT1x::requestHumidity(){
 
   // Command to send to the SHT1x to request humidity
   int _gHumidCmd = 0b00000101;
 
   // Fetch the value from the sensor
   sendCommandSHT(_gHumidCmd, _dataPin, _clockPin);
+}
+
+float SHT1x::readInHumidity(){
+  int val;                    // Raw humidity value returned from sensor
   waitForResultSHT(_dataPin);
-  _val = getData16SHT(_dataPin, _clockPin);
+  val = getData16SHT(_dataPin, _clockPin);
   skipCrcSHT(_dataPin, _clockPin);
-
-  // Apply linear conversion to raw value
-  _linearHumidity = C1 + C2 * _val + C3 * _val * _val;
-
-  // Get current temperature for humidity correction
-  _temperature = readTemperatureC();
-
-  // Correct humidity value for current temperature
-  _correctedHumidity = (_temperature - 25.0 ) * (T1 + T2 * _val) + _linearHumidity;
-
-  return (_correctedHumidity);
+  return val;
 }
 
+float SHT1x::parseHumidity(int raw){
+  float linearHumidity;       // Humidity with linear correction applied
+  float correctedHumidity;    // Temperature-corrected humidity
+  float temperature;          // Raw temperature value
 
-/* ================  Private methods ================ */
+  // Conversion coefficients from SHT15 datasheet
+  const float C1 = -4.0;       // for 12 Bit
+  const float C2 =  0.0405;    // for 12 Bit
+  const float C3 = -0.0000028; // for 12 Bit
+  const float T1 =  0.01;      // for 14 Bit
+  const float T2 =  0.00008;   // for 14 Bit
 
-/**
- * Reads the current raw temperature value
- */
-float SHT1x::readTemperatureRaw()
-{
-  int _val;
+  // Apply linear conversion to raw value
+  linearHumidity = C1 + C2 * raw + C3 * raw * raw;
 
-  // Command to send to the SHT1x to request Temperature
-  int _gTempCmd  = 0b00000011;
+  //temperature request should be accomplished right before this!
+  temperature = parseTemperatureC(_temperatureRaw);
 
-  sendCommandSHT(_gTempCmd, _dataPin, _clockPin);
-  waitForResultSHT(_dataPin);
-  _val = getData16SHT(_dataPin, _clockPin);
-  skipCrcSHT(_dataPin, _clockPin);
+  // Correct humidity value for current temperature
+  correctedHumidity = (temperature - 25.0 ) * (T1 + T2 * raw) + linearHumidity;
 
-  return (_val);
+  return correctedHumidity;
 }
 
 /**
  */
-int SHT1x::shiftIn(int _dataPin, int _clockPin, int _numBits)
+uint8_t SHT1x::shiftIn(int _dataPin, int _clockPin, int _numBits)
 {
   int ret = 0;
   int i;
-
   for (i=0; i<_numBits; ++i)
   {
      digitalWrite(_clockPin, HIGH);
-     delay(10);  // I don't know why I need this, but without it I don't get my 8 lsb of temp
      ret = ret*2 + digitalRead(_dataPin);
      digitalWrite(_clockPin, LOW);
   }
-
   return(ret);
 }
 
@@ -169,38 +205,21 @@ void SHT1x::sendCommandSHT(int _command, int _dataPin, int _clockPin)
   digitalWrite(_clockPin, HIGH);
   pinMode(_dataPin, INPUT);
   ack = digitalRead(_dataPin);
-  if (ack != LOW) {
-    //Serial.println("Ack Error 0");
-  }
+
   digitalWrite(_clockPin, LOW);
   ack = digitalRead(_dataPin);
-  if (ack != HIGH) {
-    //Serial.println("Ack Error 1");
-  }
 }
 
 /**
  */
 void SHT1x::waitForResultSHT(int _dataPin)
 {
-  int i;
-  int ack;
-
   pinMode(_dataPin, INPUT);
-
-  for(i= 0; i < 100; ++i)
-  {
-    delay(10);
-    ack = digitalRead(_dataPin);
-
-    if (ack == LOW) {
-      break;
-    }
-  }
-
-  if (ack == HIGH) {
-    //Serial.println("Ack Error 2"); // Can't do serial stuff here, need another way of reporting errors
-  }
+
+  unsigned long int start = millis();
+
+  //wait for SHT to show that its ready or move along it timeout is reached
+  while( digitalRead(_dataPin) && (millis()-start)<TIMEOUT_MILLIS );
 }
 
 /**