diff --git a/src/libDevCom/ADS1015.cpp b/src/libDevCom/ADS1015.cpp
index 8ceb540f44f276d920870cd28dee97e5b8116c1b..06b77d482e22c830a531d5232e399e92a15282f0 100644
--- a/src/libDevCom/ADS1015.cpp
+++ b/src/libDevCom/ADS1015.cpp
@@ -89,8 +89,8 @@ int32_t ADS1015::readCount(uint8_t channel) {
// write the configuration
m_com->write_reg16(static_cast<uint16_t>(Address::POINTER_CONFIG), config);
- std::this_thread::sleep_for(std::chrono::microseconds(
- 1000)); // wait for conversion delay (plus some headroom)
+ while (!conversionComplete()) {
+ }
uint16_t result =
m_com->read_reg16(static_cast<uint16_t>(Address::POINTER_CONVERT));
@@ -224,3 +224,84 @@ void ADS1015::setFullScaleRange(double val) {
m_calibration = std::make_shared<LinearCalibration>(val, m_maxValue);
this->setCalibration(m_calibration);
}
+
+double ADS1015::readDifferentialP0N1() {
+ return readDifferential(DifferentialConfig::P0_N1);
+}
+
+double ADS1015::readDifferentialP2N3() {
+ return readDifferential(DifferentialConfig::P2_N3);
+}
+
+double ADS1015::readDifferential(DifferentialConfig diff_config) {
+ int16_t counts = readCountDifferential(diff_config);
+ double multiplier = m_fullscale_range / m_maxValue;
+ logger(logINFO) << __PRETTY_FUNCTION__ << " counts = " << counts
+ << ", multiplier = " << multiplier;
+ return counts * multiplier;
+}
+
+int16_t ADS1015::readCountDifferentialP0N1() {
+ return readCountDifferential(DifferentialConfig::P0_N1);
+}
+
+int16_t ADS1015::readCountDifferentialP2N3() {
+ return readCountDifferential(DifferentialConfig::P2_N3);
+}
+
+int16_t ADS1015::readCountDifferential(DifferentialConfig diff_config) {
+ uint16_t config = 0;
+
+ // set single shot conifguration
+ setSingleShot(config);
+
+ // set the programmable gain amplifier configuration
+ setPGA(config);
+
+ // set the differential channel mux
+ switch (diff_config) {
+ case DifferentialConfig::P0_N1:
+ config |= static_cast<uint16_t>(Config::CONFIG_MUX_DIFF_P0_N1);
+ break;
+ case DifferentialConfig::P2_N3:
+ config |= static_cast<uint16_t>(Config::CONFIG_MUX_DIFF_P2_N3);
+ break;
+ default:
+ throw std::runtime_error(
+ "Invalid differential channel config provided for ADS1015 "
+ "device");
+ break;
+ }
+
+ // set the 'start signle-conversion' bit
+ setStartConversion(config);
+
+ // write the configuration
+ m_com->write_reg16(static_cast<uint16_t>(Address::POINTER_CONFIG), config);
+ while (!conversionComplete()) {
+ }
+
+ uint16_t raw_result =
+ m_com->read_reg16(static_cast<uint16_t>(Address::POINTER_CONVERT));
+
+ logger(logINFO) << __PRETTY_FUNCTION__ << " raw_result = " << raw_result;
+ // ADS1015 writes 12-bit results shifted by four, so remove the shift
+ raw_result = raw_result >> 4;
+ logger(logINFO) << __PRETTY_FUNCTION__
+ << " shifted raw_result = " << raw_result;
+
+ // differential measurements are signed, so check the sign bit
+ if (raw_result > 0x07FF) {
+ // negative number: set the sign bit
+ raw_result |= 0xF000;
+ }
+
+ // return the signed interpretation
+ return static_cast<int16_t>(raw_result);
+}
+
+bool ADS1015::conversionComplete() {
+ uint16_t reg =
+ m_com->read_reg16(static_cast<uint16_t>(Address::POINTER_CONFIG));
+ return (reg & 0x8000) != 0;
+}
diff --git a/src/libDevCom/ADS1015.h b/src/libDevCom/ADS1015.h
index 4b104c54142b35a547ae1788bb412d66962a9cac..02682d5baf5d0c5b527f81604b558d3e5b5161e9 100644
--- a/src/libDevCom/ADS1015.h
+++ b/src/libDevCom/ADS1015.h
@@ -14,8 +14,11 @@ class I2CCom;
*
* The `ADS1015` class provides a driver for the Texas Instruments low-power,
* I2C compatible 4-channel 12-bit ADC. Support for single-shot ADC conversions
- * is supported, whereas the differential measurement capabilities of the
- * ADS1015 are not.
+ * is supported across all four channels in single-ended measurement mode.
+ * Support for differential measurements are supported in the following
+ * configuration:
+ * - Across channel 0 and 1: channel 0 as AINP and channel 1 as AINN
+ * - Across channel 2 and 3: channel 2 as AINP and channel 3 as AINN
*
* [Datasheet](https://cdn.sparkfun.com/assets/a/c/4/9/b/ads1015.pdf)
*/
@@ -85,6 +88,22 @@ class ADS1015 : public ADCDevice {
*/
void setFullScaleRange(double val);
+ //! \brief Return the differential measurement with channel 0 as AINP and
+ //! channel 1 as AINN
+ int16_t readCountDifferentialP0N1();
+
+ //! \brief Return the differential measurement with channel 2 as AINP and
+ //! channel 3 as AINN
+ int16_t readCountDifferentialP2N3();
+
+ //! \brief Return the differential measurement between channel 0 (AINP) and
+ //! channel 1 (AINN) converted to Volts
+ double readDifferentialP0N1();
+
+ //! \brief Return the differential measurement between channel 2 (AINP) and
+ //! channel 3 (AINN) converted to Volts)
+ double readDifferentialP2N3();
+
private:
void init(double full_scale_range, std::shared_ptr<I2CCom> com);
@@ -156,6 +175,15 @@ class ADS1015 : public ADCDevice {
// in high state (default)
};
+ // The ADS1015 can be configured for differential measurements with the
+ // negative channel being either channel 1 or channel 3, however it is
+ // recommended to only perform differential measurements between the
+ // adjacent channels due to the internal capacitive network. This enum
+ // defines the possible differential measurement configuration, but is not
+ // known to the user which will call the more direct `readDifferentialP0N1`
+ // and `readDifferentialP2N3` methods.
+ enum class DifferentialConfig { P0_N1, P2_N3 };
+
// map between programmable gain configuration and ADS1015 full scale range
// in volts
const std::map<Gain, std::string> gainToFSRMap{
@@ -185,6 +213,7 @@ class ADS1015 : public ADCDevice {
double m_fullscale_range; // volts
// some helper methods
+ bool conversionComplete();
Gain fsrToGain(double fsr);
std::string fsrToString();
std::string fsrValToString(double val);
@@ -195,6 +224,10 @@ class ADS1015 : public ADCDevice {
void setPGA(uint16_t& config);
void setSingleChannel(uint16_t& config, uint8_t channel);
void setStartConversion(uint16_t& config);
+
+ // methods for performing differential measurement
+ int16_t readCountDifferential(DifferentialConfig config);
+ double readDifferential(DifferentialConfig config);
};
#endif // DEVCOM_ADS1015_H