Merge pull request #61 from caternuson/volts

Add volts and other tweaks

Author: caternuson

Adafruit_ADS1X15.cpp

@@ -110,7 +110,7 @@ uint16_t Adafruit_ADS1X15::getDataRate() { return m_dataRate; }
     @return the ADC reading
 */
 /**************************************************************************/
-uint16_t Adafruit_ADS1X15::readADC_SingleEnded(uint8_t channel) {
+int16_t Adafruit_ADS1X15::readADC_SingleEnded(uint8_t channel) {
   if (channel > 3) {
     return 0;
   }
@@ -156,8 +156,7 @@ uint16_t Adafruit_ADS1X15::readADC_SingleEnded(uint8_t channel) {
     ;
 
   // Read the conversion results
-  // Shift 12-bit results right 4 bits for the ADS1015
-  return readRegister(ADS1X15_REG_POINTER_CONVERT) >> m_bitShift;
+  return getLastConversionResults();
 }
 
 /**************************************************************************/
@@ -199,18 +198,7 @@ int16_t Adafruit_ADS1X15::readADC_Differential_0_1() {
     ;
 
   // Read the conversion results
-  uint16_t res = readRegister(ADS1X15_REG_POINTER_CONVERT) >> m_bitShift;
-  if (m_bitShift == 0) {
-    return (int16_t)res;
-  } else {
-    // Shift 12-bit results right 4 bits for the ADS1015,
-    // making sure we keep the sign bit intact
-    if (res > 0x07FF) {
-      // negative number - extend the sign to 16th bit
-      res |= 0xF000;
-    }
-    return (int16_t)res;
-  }
+  return getLastConversionResults();
 }
 
 /**************************************************************************/
@@ -252,18 +240,7 @@ int16_t Adafruit_ADS1X15::readADC_Differential_2_3() {
     ;
 
   // Read the conversion results
-  uint16_t res = readRegister(ADS1X15_REG_POINTER_CONVERT) >> m_bitShift;
-  if (m_bitShift == 0) {
-    return (int16_t)res;
-  } else {
-    // Shift 12-bit results right 4 bits for the ADS1015,
-    // making sure we keep the sign bit intact
-    if (res > 0x07FF) {
-      // negative number - extend the sign to 16th bit
-      res |= 0xF000;
-    }
-    return (int16_t)res;
-  }
+  return getLastConversionResults();
 }
 
 /**************************************************************************/
@@ -345,6 +322,43 @@ int16_t Adafruit_ADS1X15::getLastConversionResults() {
   }
 }
 
+/**************************************************************************/
+/*!
+    @brief  Returns true if conversion is complete, false otherwise.
+
+    @param counts the ADC reading in raw counts
+
+    @return the ADC reading in volts
+*/
+/**************************************************************************/
+float Adafruit_ADS1X15::computeVolts(int16_t counts) {
+  // see data sheet Table 3
+  float fsRange;
+  switch (m_gain) {
+  case GAIN_TWOTHIRDS:
+    fsRange = 6.144f;
+    break;
+  case GAIN_ONE:
+    fsRange = 4.096f;
+    break;
+  case GAIN_TWO:
+    fsRange = 2.048f;
+    break;
+  case GAIN_FOUR:
+    fsRange = 1.024f;
+    break;
+  case GAIN_EIGHT:
+    fsRange = 0.512f;
+    break;
+  case GAIN_SIXTEEN:
+    fsRange = 0.256f;
+    break;
+  default:
+    fsRange = 0.0f;
+  }
+  return counts * (fsRange / (32768 >> m_bitShift));
+}
+
 /**************************************************************************/
 /*!
     @brief  Returns true if conversion is complete, false otherwise.

Adafruit_ADS1X15.h

@@ -148,11 +148,12 @@ class Adafruit_ADS1X15 {
 
 public:
   void begin(uint8_t i2c_addr = ADS1X15_ADDRESS, TwoWire *wire = &Wire);
-  uint16_t readADC_SingleEnded(uint8_t channel);
+  int16_t readADC_SingleEnded(uint8_t channel);
   int16_t readADC_Differential_0_1();
   int16_t readADC_Differential_2_3();
   void startComparator_SingleEnded(uint8_t channel, int16_t threshold);
   int16_t getLastConversionResults();
+  float computeVolts(int16_t counts);
   void setGain(adsGain_t gain);
   adsGain_t getGain();
   void setDataRate(uint16_t rate);

examples/singleended/singleended.ino

@@ -1,6 +1,6 @@
 #include <Adafruit_ADS1X15.h>
 
-// Adafruit_ADS1115 ads;  /* Use this for the 16-bit version */
+//Adafruit_ADS1115 ads;  /* Use this for the 16-bit version */
 Adafruit_ADS1015 ads;     /* Use this for the 12-bit version */
 
 void setup(void) 
@@ -30,16 +30,23 @@ void setup(void)
 void loop(void) 
 {
   int16_t adc0, adc1, adc2, adc3;
+  float volts0, volts1, volts2, volts3;
 
   adc0 = ads.readADC_SingleEnded(0);
   adc1 = ads.readADC_SingleEnded(1);
   adc2 = ads.readADC_SingleEnded(2);
   adc3 = ads.readADC_SingleEnded(3);
-  Serial.print("AIN0: "); Serial.println(adc0);
-  Serial.print("AIN1: "); Serial.println(adc1);
-  Serial.print("AIN2: "); Serial.println(adc2);
-  Serial.print("AIN3: "); Serial.println(adc3);
-  Serial.println(" ");
-  
+
+  volts0 = ads.computeVolts(adc0);
+  volts1 = ads.computeVolts(adc1);
+  volts2 = ads.computeVolts(adc2);
+  volts3 = ads.computeVolts(adc3);
+
+  Serial.println("-----------------------------------------------------------");
+  Serial.print("AIN0: "); Serial.print(adc0); Serial.print("  "); Serial.print(volts0); Serial.println("V");
+  Serial.print("AIN1: "); Serial.print(adc1); Serial.print("  "); Serial.print(volts1); Serial.println("V");
+  Serial.print("AIN2: "); Serial.print(adc2); Serial.print("  "); Serial.print(volts2); Serial.println("V");
+  Serial.print("AIN3: "); Serial.print(adc3); Serial.print("  "); Serial.print(volts3); Serial.println("V");
+
   delay(1000);
 }

keywords.txt

@@ -6,5 +6,8 @@ readADC_Differential_0_1	KEYWORD2
 readADC_Differential_2_3	KEYWORD2
 startComparator_SingleEnded	KEYWORD2
 getLastConversionResults	KEYWORD2
+computeVolts	KEYWORD2
 setGain	KEYWORD2
-getGain	KEYWORD2
+getGain	KEYWORD2
+setDataRate	KEYWORD2
+getDataRate	KEYWORD2

library.properties

@@ -1,5 +1,5 @@
 name=Adafruit ADS1X15
-version=2.0.1
+version=2.1.0
 author=Adafruit
 maintainer=Adafruit <info@adafruit.com>
 sentence=Arduino library for ADS1015/1115 ADCs.