Merge pull request #73 from MrF83/master

Added support for Differential measuring between AIN0 to AIN3 and AIN1 to AIN3.

Adafruit_ADS1X15.cpp

@@ -203,6 +203,88 @@ int16_t Adafruit_ADS1X15::readADC_Differential_0_1() {
   return getLastConversionResults();
 }
 
+/**************************************************************************/
+/*!
+    @brief  Reads the conversion results, measuring the voltage
+            difference between the P (AIN0) and N (AIN3) input.  Generates
+            a signed value since the difference can be either
+            positive or negative.
+    @return the ADC reading
+*/
+/**************************************************************************/
+int16_t Adafruit_ADS1X15::readADC_Differential_0_3() {
+  // Start with default values
+  uint16_t config =
+      ADS1X15_REG_CONFIG_CQUE_NONE |    // Disable the comparator (default val)
+      ADS1X15_REG_CONFIG_CLAT_NONLAT |  // Non-latching (default val)
+      ADS1X15_REG_CONFIG_CPOL_ACTVLOW | // Alert/Rdy active low   (default val)
+      ADS1X15_REG_CONFIG_CMODE_TRAD |   // Traditional comparator (default val)
+      ADS1X15_REG_CONFIG_MODE_SINGLE;   // Single-shot mode (default)
+
+  // Set PGA/voltage range
+  config |= m_gain;
+
+  // Set data rate
+  config |= m_dataRate;
+
+  // Set channels
+  config |= ADS1X15_REG_CONFIG_MUX_DIFF_0_3; // AIN0 = P, AIN3 = N
+
+  // Set 'start single-conversion' bit
+  config |= ADS1X15_REG_CONFIG_OS_SINGLE;
+
+  // Write config register to the ADC
+  writeRegister(ADS1X15_REG_POINTER_CONFIG, config);
+
+  // Wait for the conversion to complete
+  while (!conversionComplete())
+    ;
+
+  // Read the conversion results
+  return getLastConversionResults();
+}
+
+/**************************************************************************/
+/*!
+    @brief  Reads the conversion results, measuring the voltage
+            difference between the P (AIN1) and N (AIN3) input.  Generates
+            a signed value since the difference can be either
+            positive or negative.
+    @return the ADC reading
+*/
+/**************************************************************************/
+int16_t Adafruit_ADS1X15::readADC_Differential_1_3() {
+  // Start with default values
+  uint16_t config =
+      ADS1X15_REG_CONFIG_CQUE_NONE |    // Disable the comparator (default val)
+      ADS1X15_REG_CONFIG_CLAT_NONLAT |  // Non-latching (default val)
+      ADS1X15_REG_CONFIG_CPOL_ACTVLOW | // Alert/Rdy active low   (default val)
+      ADS1X15_REG_CONFIG_CMODE_TRAD |   // Traditional comparator (default val)
+      ADS1X15_REG_CONFIG_MODE_SINGLE;   // Single-shot mode (default)
+
+  // Set PGA/voltage range
+  config |= m_gain;
+
+  // Set data rate
+  config |= m_dataRate;
+
+  // Set channels
+  config |= ADS1X15_REG_CONFIG_MUX_DIFF_1_3; // AIN1 = P, AIN3 = N
+
+  // Set 'start single-conversion' bit
+  config |= ADS1X15_REG_CONFIG_OS_SINGLE;
+
+  // Write config register to the ADC
+  writeRegister(ADS1X15_REG_POINTER_CONFIG, config);
+
+  // Wait for the conversion to complete
+  while (!conversionComplete())
+    ;
+
+  // Read the conversion results
+  return getLastConversionResults();
+}
+
 /**************************************************************************/
 /*!
     @brief  Reads the conversion results, measuring the voltage

Adafruit_ADS1X15.h

@@ -150,6 +150,8 @@ class Adafruit_ADS1X15 {
   bool begin(uint8_t i2c_addr = ADS1X15_ADDRESS, TwoWire *wire = &Wire);
   int16_t readADC_SingleEnded(uint8_t channel);
   int16_t readADC_Differential_0_1();
+  int16_t readADC_Differential_0_3();
+  int16_t readADC_Differential_1_3();
   int16_t readADC_Differential_2_3();
   void startComparator_SingleEnded(uint8_t channel, int16_t threshold);
   int16_t getLastConversionResults();
@@ -186,4 +188,4 @@ class Adafruit_ADS1115 : public Adafruit_ADS1X15 {
   Adafruit_ADS1115();
 };
 
-#endif
+#endif