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Erriez · Aug 31, 2020 · c3f163d · c3f163d
1 parent 3dbd05a
commit c3f163d
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Showing 3 changed files with 22 additions and 22 deletions.
diff --git a/ErriezMHZ19B.pdf b/ErriezMHZ19B.pdf
diff --git a/src/ErriezMHZ19B.cpp b/src/ErriezMHZ19B.cpp
@@ -65,7 +65,7 @@ ErriezMHZ19B::~ErriezMHZ19B()
  * \retval true
  *      Sensor detected.
  * \retval false
- *      Sensor not detected.
+ *      Sensor not detected, check wiring/power.
  */
 bool ErriezMHZ19B::detect()
 {
@@ -125,7 +125,10 @@ bool ErriezMHZ19B::isWarmingUp()
  * \brief Check minimum interval between CO2 reads
  * \details
  *      Not described in the datasheet, but it is the same frequency as the built-in LED blink.
- * \return
+ * \retval true
+ *      Ready to call readCO2().
+ * \retval false
+ *      Conversion not completed.
  */
 bool ErriezMHZ19B::isReady()
 {
@@ -164,6 +167,7 @@ int16_t ErriezMHZ19B::readCO2()
 
     // Check result
     if (result == MHZ19B_RESULT_OK) {
+        // 16-bit CO2 value in response Bytes 2 and 3
         result = (rxBuffer[2] << 8) | rxBuffer[3];
     }
 
@@ -201,8 +205,9 @@ int8_t ErriezMHZ19B::getVersion(char *version, uint8_t versionLen)
     if (result == MHZ19B_RESULT_OK) {
         // Copy 4 ASCII characters to version array like "0443"
         for (uint8_t i = 0; i < 4; i++) {
+            // Version in response Bytes 2..5
             version[i] = rxBuffer[i + 2];
-        };
+        }
     }
 
     return result;
@@ -283,9 +288,9 @@ int8_t ErriezMHZ19B::setAutoCalibration(bool calibrationOn)
  * \brief Get status automatic calibration (NOT DOCUMENTED)
  * \retval <0
  *      MH-Z19B response error codes.
- * \retval true
+ * \retval 1
  *      Automatic calibration on.
- * \retval false
+ * \retval 0
  *      Automatic calibration off.
  */
 int8_t ErriezMHZ19B::getAutoCalibration()
@@ -297,14 +302,8 @@ int8_t ErriezMHZ19B::getAutoCalibration()
 
     // Check result
     if (result == MHZ19B_RESULT_OK) {
-        // Response is located in Byte 7
-        if (rxBuffer[7] == 0x01) {
-            // On
-            result = 1;
-        } else if (rxBuffer[7] == 0x00) {
-            // Off
-            result = 0;
-        }
+        // Response is located in Byte 7: 0 = off, 1 = on
+        result = rxBuffer[7] & 0x01;
     }
 
     return result;
@@ -328,7 +327,8 @@ int8_t ErriezMHZ19B::startZeroCalibration()
 /*!
  * \brief Send serial command to sensor and read response
  * \details
- *      Send command to sensor and read response, protected with a receive timeout.
+ *      Send command to sensor and read response, protected with a receive timeout.\n
+ *      Result is available in public rxBuffer[9].
  * \param cmd
  *      Command Byte
  * \param b3
@@ -370,7 +370,7 @@ int8_t ErriezMHZ19B::sendCommand(uint8_t cmd, byte b3, byte b4, byte b5, byte b6
     // Clear receive buffer
     memset(rxBuffer, 0, sizeof(rxBuffer));
 
-    // Wait until all data received from sensor
+    // Wait until all data received from sensor with receive timeout protection
     tStart = millis();
     while (_serial->available() < MHZ19B_SERIAL_RX_BYTES) {
         if ((millis() - tStart) >= MHZ19B_SERIAL_RX_TIMEOUT_MS) {

diff --git a/src/ErriezMHZ19B.h b/src/ErriezMHZ19B.h
@@ -97,7 +97,7 @@ class ErriezMHZ19B
     // Detect sensor by checking range response
     bool detect();
 
-    // Is warming-up (minimum wait time after power-on)
+    // Minimum wait time after power-on
     bool isWarmingUp();
 
     // Minimum wait time between CO2 reads
@@ -109,14 +109,14 @@ class ErriezMHZ19B
     // Get firmware version (NOT DOCUMENTED)
     int8_t getVersion(char *version, uint8_t versionLen);
 
-    // Set/get CO2 range
+    // Set/get CO2 range, default 5000ppm)
     int8_t setRange2000ppm();
     int8_t setRange5000ppm();
     int16_t getRange(); // (NOT DOCUMENTED)
 
-    // Set and get ABC (Automatic Baseline Correction)
+    // Set and get ABC, default on (Automatic Baseline Correction)
     int8_t setAutoCalibration(bool calibrationOn);
-    int8_t getAutoCalibration();  // (NOT DOCUMENTED)
+    int8_t getAutoCalibration(); // (NOT DOCUMENTED)
 
     // Start Zero Point Calibration manually at 400ppm
     int8_t startZeroCalibration();
@@ -128,10 +128,10 @@ class ErriezMHZ19B
     uint8_t rxBuffer[MHZ19B_SERIAL_RX_BYTES];
 
 private:
-    Stream *_serial;
-    unsigned long _tLastReadCO2;
+    Stream *_serial;                //!< Serial Stream pointer
+    unsigned long _tLastReadCO2;    //!< Timestamp between readCO2() calls
 
-    // Serial communication functions
+    // CRC check on serial transmit/receive buffer
     uint8_t calcCRC(uint8_t *data);
 };