0.1.4 add crc + error handling (#5)

README.md

@@ -55,7 +55,7 @@ The SGP30 sensor has a fixed I2C address so only one sensor per I2C bus can be u
 - **SGP30(TwoWire \*wire = &Wire)** Constructor with optional the Wire interface as parameter.
 - **bool begin()** .
 - **bool begin(sda, scl)** idem, for the ESP32 where one can choose the I2C pins.
-- **bool isConnected()** checks if the address is visable on the I2C bus.
+- **bool isConnected()** checks if the address is visible on the I2C bus.
 
 
 ### Meta
@@ -67,7 +67,7 @@ The SGP30 sensor has a fixed I2C address so only one sensor per I2C bus can be u
 
 ### Synchronous measurements
 
-- **uint32_t lastMeasurement()** timestamp in millis of the last sync measurement made. This convenience function is useful to prevent reading the sensor too often.
+- **uint32_t lastMeasurement()** timestamp in milliseconds of the last sync measurement made. This convenience function is useful to prevent reading the sensor too often.
 - **bool measure(bool all = false)** if all == false, only the TVOC and CO2 are updated (slow due to blocking), if all == true, also the H2 and the Ethanol values are updated (even slower). Note the measurement is slow as there is an active blocking until the sensor is done. If the last measurement is less than a second ago, no measurement is made and the function returns false.
 
 
@@ -76,9 +76,9 @@ The SGP30 sensor has a fixed I2C address so only one sensor per I2C bus can be u
 With the async interface, the user should control that reads are at least one second apart. The user should also take care not to mix up different requests. See examples. 
 
 - **void request()** sends a request to the sensor to read CO2 and TVOC. 
-- **bool read()** returns true if the last request is more than 12 millis ago the CO2 and TVOC are read and updated. Otherwise false is returned.
+- **bool read()** returns true if the last request is more than 12 milliseconds ago the CO2 and TVOC are read and updated. Otherwise false is returned.
 - **void requestRaw()** sends a request to the sensor to read H2 and Ethanol.
-- **bool readRaw()** returns true if the last request is more than 25 millis ago the H2 and Ethanol are read and updated. Otherwise false is returned.
+- **bool readRaw()** returns true if the last request is more than 25 milliseconds ago the H2 and Ethanol are read and updated. Otherwise false is returned.
 
 
 ### Get the data
@@ -127,6 +127,7 @@ use at own risk.
 Since 0.1.2 the library has experimental support for H2 and Ethanol concentration in ppm. 
 
 One should use these functions more as a relative indication than as an absolute measurement as it is definitely not calibrated.
+Runs with different temperature and humidity (different days) give very different values including overflow and infinity.
 
 - **float getH2()** gets the H2 concentration. Units ppm.
 - **float getEthanol()** gets the Ethanol concentration. Units ppm.
@@ -142,10 +143,12 @@ The used references are based upon (1) averaging raw data in outside air at 22°
 ## Todo
 
 - redo **getID()**
-- redo **lastError()**
 - test test test ....
-- CRC handling
-- error handling
+
+
+The CRC checking + error handling (since 0.1.4) adds around 330 bytes PROGMEM on an UNO.
+There might be a need for a minimal class that only reads CO2 and TVOC, no baselines etc.
+for the smallest platforms. 
 
 
 ## Operational

SGP30.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: SGP30.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.3
+// VERSION: 0.1.4
 //    DATE: 2021-06-24
 // PURPOSE: SGP30 library for Arduino
 //     URL: https://github.com/RobTillaart/SGP30
@@ -12,6 +12,7 @@
 //  0.1.1   2021-06-26  add get/setBaseline ++
 //  0.1.2   2021-06-26  experimental add units  H2 + Ethanol
 //  0.1.3   2021-06-26  add get/setTVOCbaseline()
+//  0.1.4   2021-07-01  add CRC checking
 
 
 #include "SGP30.h"
@@ -79,10 +80,18 @@ bool SGP30::getID()
     {
       _id[j++] = _wire->read();
       _id[j++] = _wire->read();
-      _wire->read();        // skip crc
+      uint8_t crc = _wire->read();
+      uint16_t val = _id[j-2] * 256 + _id[j-1];
+      if (_CRC8(val) != crc)
+      {
+        _error = SGP30_ERROR_CRC;
+        return false;
+      }
     }
+    _error = SGP30_OK;
     return true;
   }
+  _error = SGP30_ERROR_I2C;
   return false;
 }
 
@@ -97,9 +106,17 @@ uint16_t SGP30::getFeatureSet()
   {
     rv = _wire->read() << 8;
     rv  += _wire->read();
-    _wire->read();       // skip crc
+    uint8_t crc = _wire->read();
+    if (_CRC8(rv) != crc)
+    {
+      _error = SGP30_ERROR_CRC;
+      return rv;
+    }
+    _error = SGP30_OK;
+    return rv;
   }
-  return rv;
+  _error = SGP30_ERROR_I2C;
+  return 0xFFFF;
 }
 
 
@@ -120,9 +137,16 @@ bool SGP30::measureTest()
   {
     rv = _wire->read() << 8;
     rv  += _wire->read();
-    _wire->read();       // skip crc
+    uint8_t crc = _wire->read();
+    if (_CRC8(rv) != crc)
+    {
+      _error = SGP30_ERROR_CRC;
+      return false;
+    }
+    _error = SGP30_OK;
     return rv == 0xD400;
   }
+  _error = SGP30_ERROR_I2C;
   return false;
 }
 
@@ -166,19 +190,28 @@ bool SGP30::read()
   if (millis() - _lastRequest < 13) return false;  // P11
   _lastRequest = 0;
 
-  // TODO error handling
-  // TODO CRC
   if (_wire->requestFrom(_address, (uint8_t)6) != 6)
   {
+    _error = SGP30_ERROR_I2C;
     return false;
   }
   _co2  =  _wire->read() << 8;
   _co2  += _wire->read();
-           _wire->read();       // skip crc
-
+  uint8_t crc = _wire->read();
+  if (_CRC8(_co2) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
   _tvoc =  _wire->read() << 8;
   _tvoc += _wire->read();
-           _wire->read();       // skip crc
+  crc = _wire->read();
+  if (_CRC8(_tvoc) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
+  _error = SGP30_OK;
   return true;
 }
 
@@ -196,18 +229,28 @@ bool SGP30::readRaw()
   if (millis() - _lastRequest < 26) return false;  // P11
   _lastRequest = 0;
 
-  // TODO error handling
-  // TODO CRC
   if (_wire->requestFrom(_address, (uint8_t)6) != 6)
   {
+    _error = SGP30_ERROR_I2C;
     return false;
   }
   _h2      =  _wire->read() << 8;
   _h2      += _wire->read();
-              _wire->read();        // skip crc
+  uint8_t crc = _wire->read();
+  if (_CRC8(_h2) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
   _ethanol =  _wire->read() << 8;
   _ethanol += _wire->read();
-              _wire->read();        // skip crc
+  crc = _wire->read();
+  if (_CRC8(_ethanol) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
+  _error = SGP30_OK;
   return true;
 }
 
@@ -268,18 +311,28 @@ void SGP30::setBaseline(uint16_t CO2, uint16_t TVOC)
 bool SGP30::getBaseline(uint16_t *CO2, uint16_t *TVOC)
 {
   _command(0x2015);
-  // TODO error handling
-  // TODO CRC
   if (_wire->requestFrom(_address, (uint8_t)6) != 6)
   {
+    _error = SGP30_ERROR_I2C;
     return false;
   }
   *CO2  =  _wire->read() << 8;
   *CO2  += _wire->read();
-           _wire->read();        // skip crc
+  uint8_t crc = _wire->read();
+  if (_CRC8(*CO2) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
   *TVOC =  _wire->read() << 8;
   *TVOC += _wire->read();
-           _wire->read();        // skip crc
+  crc = _wire->read();
+  if (_CRC8(*TVOC) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
+  _error = SGP30_OK;
   return true;
 }
 
@@ -293,15 +346,20 @@ void SGP30::setTVOCBaseline(uint16_t TVOC)
 bool SGP30::getTVOCBaseline(uint16_t *TVOC)
 {
   _command(0x20B3);
-  // TODO error handling
-  // TODO CRC
   if (_wire->requestFrom(_address, (uint8_t)3) != 3)
   {
+    _error = SGP30_ERROR_I2C;
     return false;
   }
   *TVOC =  _wire->read() << 8;
   *TVOC += _wire->read();
-           _wire->read();        // skip crc
+  uint8_t crc = _wire->read();
+  if (_CRC8(*TVOC) != crc)
+  {
+    _error = SGP30_ERROR_CRC;
+    return false;
+  }
+  _error = SGP30_OK;
   return true;
 }
 

SGP30.h

@@ -2,7 +2,7 @@
 //
 //    FILE: SGP30.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.3
+// VERSION: 0.1.4
 //    DATE: 2021-06-24
 // PURPOSE: SGP30 library for Arduino
 //     URL: https://github.com/RobTillaart/SGP30
@@ -12,9 +12,11 @@
 #include "Arduino.h"
 #include "Wire.h"
 
-#define SGP30_LIB_VERSION         (F("0.1.3"))
+#define SGP30_LIB_VERSION         (F("0.1.4"))
 
 #define SGP30_OK                  0x00
+#define SGP30_ERROR_CRC           0xFF
+#define SGP30_ERROR_I2C           0xFE
 
 
 class SGP30
@@ -56,14 +58,15 @@ class SGP30
   uint16_t getCO2()         { return _co2; };      // PPM
   uint16_t getH2_raw()      { return _h2; };       // UNKNOWN
   uint16_t getEthanol_raw() { return _ethanol; };  // UNKNOWN
-  float getH2();            // experimental        // PPM
-  float getEthanol();       // experimental        // PPM
+  float    getH2();         // experimental        // PPM
+  float    getEthanol();    // experimental        // PPM
 
 
   // CALIBRATION - read datasheet
   // T  in °C
   // RH == 0..100
   float    setRelHumidity(float T, float RH);  // P10
+  // Absolute humidity in grams / m3
   // set Abs Hum to 0 to disables it...
   void     setAbsHumidity(float AbsoluteHumidity);
 

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/SGP30.git"
   },
-  "version": "0.1.3",
+  "version": "0.1.4",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*"

library.properties

@@ -1,5 +1,5 @@
 name=SGP30
-version=0.1.3
+version=0.1.4
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for SGP30 environment sensor.