Merge pull request #2 from RobTillaart/develop

add get/set baseline ++

README.md

@@ -11,14 +11,18 @@ Warning: experimental, 0.1.0 is functional not complete.
 
 ## Description
 
-The SVP30 from Sensirion is an environment sensor that measures H2 and Ethanol in the air. From these numbers an intern algorithm derives an CO2 equivalent and a TVOC measurement. 
+The SGP30 from Sensirion is an environment sensor that measures H2 and Ethanol in the air. From these numbers an intern algorithm derives an CO2 equivalent and a TVOC measurement. 
 
 The CO2 units are ppm, the TVOC units are ppb. Units for H2 and Ethanol are unknown. For larger concentrations the resolution drops, see datasheet.
 
-The sensor can be read up to once per second (1 Hz).
+The CO2 and TVOC values can be read up to once per second (1 Hz). Ethanol and H2, the raw data can be sampled up to 40 Hz.
 
 The library supports 2 types of interfaces, a synchronous and an asynchronous interface. The sync interface is blocking for up to 40 milliseconds which was enough to trigger the implementation of an async interface. Note: the sync interface is implemented with the async interface.
 
+The SGP30 works with I2C bus at 100 KHz and 400 KHz. In a short test it worked well up to 600 KHz. A faster I2C clock does not give the sync interface much (relative) gain, however for the async the relative gain is much more.
+
+It may take up to 10 seconds (maybe more) before the sensor produces real data.
+
 
 #### multi sensors.
 
@@ -65,47 +69,51 @@ The library caches the last read values, and these are the functions to access t
 - **uint16_t getTVOC()** gets the TVOC concentration (ppb)
 - **uint16_t getCO2()** gets the CO2 **equivalent** concentration (ppm)
 - **uint16_t getH2()** gets the H2 concentration. Units unknown.
-- **uint16_t getEthanol()** gets the Ethanol concnetration. Units unknown.
+- **uint16_t getEthanol()** gets the Ethanol concentration. Units unknown.
 
 
 ### Calibration
 
-- **float setRelHumidity(float T, float RH)** sets the compensation for temperature and **relative** humidity. These values can be obtained e.g. from an SHT30, DHT22 or similar sensor.
-- **void setAbsHumidity(float AbsoluteHumidity)** sets the compensation for **absolute** humidity. 
+Check the datasheet for operating range, figure 7.
+
+- **float setRelHumidity(float T, float RH)** sets the compensation for temperature (5-55°C) and **relative** humidity (10-95%). These values can be obtained e.g. from an SHT30, DHT22 or similar sensor.
+- **void setAbsHumidity(float AbsoluteHumidity)** sets the compensation for **absolute** humidity. Concentration is in gram per cubic meter (g/m3)
 
 
 ### Baseline functions
 
-- TODO
+The baseline functions give the sensor a reference value. After running in a known condition e.g. outside in open air, one can get the baseline values as a sort of calibration. Please read the datasheet carefully before using these functions.
 
+Note: if the sensor has no reads done, these values tend to go to zero. This is because the baselines are based upon recent reads.
 
-### MISC
+- **bool getBaseline(uint16_t *CO2, uint16_t *TVOC)**
+- **void setBaseline(uint16_t CO2, uint16_t TVOC)** 
 
-- **int lastError()** returns last error. (needs rework)
 
+### Misc
 
+- **int lastError()** returns last error. (needs rework)
 
-## Todo
 
-No particular order.
+## Todo
 
-- measure performance at different I2C speeds.
-- get units H2 right
-- get units Ethanol right
 - redo **getID()**
 - redo **lastError()**
 - should **getFeatureSet()** become **bool checkFeatureSet()**?
-- implement get Acquisition Baseline() functions.
+- implement the TVOC starter baseline.
 - test test test ....
-= extend unit tests
-- improve documentation
+- get units H2 right if possible
+- get units Ethanol right if possible
+- CRC handling
+- error handling
 
 
 ## Operational
 
 See examples
 
+
 ## Links
 
-https://www.adafruit.com/product/3709
+https://www.adafruit.com/product/3709 - the sensor.
 

SGP30.cpp

@@ -1,15 +1,15 @@
 //
 //    FILE: SGP30.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
+// VERSION: 0.1.1
 //    DATE: 2021-06-24
 // PURPOSE: SGP30 library for Arduino
 //     URL: https://github.com/RobTillaart/SGP30
 //          https://www.adafruit.com/product/3709
 //
 //  HISTORY:
 //  0.1.0   2021-06-24 initial version
-//
+//  0.1.1   2021-06-26 add get/setBaseline ++
 
 
 #include "SGP30.h"
@@ -187,6 +187,7 @@ void SGP30::requestRaw()
   _command(0x2050);
 }
 
+
 bool SGP30::readRaw()
 {
   if (_lastRequest == 0) return false;
@@ -202,15 +203,13 @@ bool SGP30::readRaw()
   _h2      =  _wire->read() << 8;
   _h2      += _wire->read();
               _wire->read();        // skip crc
-
   _ethanol =  _wire->read() << 8;
   _ethanol += _wire->read();
               _wire->read();        // skip crc
   return true;
 }
 
 
-
 /////////////////////////////////////////////////////
 //
 // CALIBRATION
@@ -238,7 +237,32 @@ void SGP30::setAbsHumidity(float AbsoluteHumidity)
   uint8_t tmp = (AbsoluteHumidity - AH) * 256;
   AH = (AH << 8) | tmp;
 
-  _setCommand(0x2061, AH);   // P 11
+  _command(0x2061, AH);     // P 11
+}
+
+
+void SGP30::setBaseline(uint16_t CO2, uint16_t TVOC)
+{
+  _command(0x201E, CO2, 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)
+  {
+    return false;
+  }
+  *CO2  =  _wire->read() << 8;
+  *CO2  += _wire->read();
+           _wire->read();        // skip crc
+  *TVOC =  _wire->read() << 8;
+  *TVOC += _wire->read();
+           _wire->read();        // skip crc
+  return true;
 }
 
 
@@ -268,14 +292,30 @@ int SGP30::_command(uint16_t cmd)
 }
 
 
-int SGP30::_setCommand(uint16_t cmd, uint16_t val)
+int SGP30::_command(uint16_t cmd, uint16_t v1)
+{
+  _wire->beginTransmission(_address);
+  _wire->write(cmd >> 8);
+  _wire->write(cmd & 0xFF);
+  _wire->write(v1 >> 8);
+  _wire->write(v1 & 0xFF);
+  _wire->write(_CRC8(v1));
+  _error = _wire->endTransmission();
+  return _error;
+}
+
+
+int SGP30::_command(uint16_t cmd, uint16_t v1, uint16_t v2)
 {
   _wire->beginTransmission(_address);
   _wire->write(cmd >> 8);
   _wire->write(cmd & 0xFF);
-  _wire->write(val >> 8);
-  _wire->write(val & 0xFF);
-  _wire->write(_CRC8(val));
+  _wire->write(v1 >> 8);
+  _wire->write(v1 & 0xFF);
+  _wire->write(_CRC8(v1));
+  _wire->write(v2 >> 8);
+  _wire->write(v2 & 0xFF);
+  _wire->write(_CRC8(v2));
   _error = _wire->endTransmission();
   return _error;
 }
@@ -288,7 +328,8 @@ uint8_t SGP30::_CRC8(uint16_t data)
   uint8_t val[2];
   val[0] = data >> 8;
   val[1] = data & 0xFF;
-  uint8_t crc = 0xFF;
+
+  uint8_t crc = 0xFF;             // start value
   for(uint8_t i = 0; i < 2; i++) 
   {
     crc ^= val[i];

SGP30.h

@@ -2,7 +2,7 @@
 //
 //    FILE: SGP30.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
+// VERSION: 0.1.1
 //    DATE: 2021-06-24
 // PURPOSE: SGP30 library for Arduino
 //     URL: https://github.com/RobTillaart/SGP30
@@ -12,7 +12,7 @@
 #include "Arduino.h"
 #include "Wire.h"
 
-#define SGP30_LIB_VERSION         (F("0.1.0"))
+#define SGP30_LIB_VERSION         (F("0.1.1"))
 
 #define SGP30_OK                  0x00
 
@@ -65,18 +65,13 @@ class SGP30
   // set Abs Hum to 0 to disables it...
   void     setAbsHumidity(float AbsoluteHumidity);
 
-  // TODO NEXT RELEASE
-/*
-  something like this
-
-  void     setAcqBase() {};   // 0x201e
-  void     getAcqBase() {};   // 0x2015
-  void     setTVOCBase() {};  // 0x2077
-  void     getTVOCBase() {};  // 0x20B3
+  void     setBaseline(uint16_t CO2, uint16_t TVOC);
+  bool     getBaseline(uint16_t *CO2, uint16_t *TVOC);
 
-  split getAcqBase in 2 calls?
-  uint16_t getCO2base();
-  uint16_t getTVOCbase();
+/*
+  // faster startup
+  void     setTVOCStarter() {};  // 0x2077
+  void     getTVOCStarter() {};  // 0x20B3
 */
 
 
@@ -92,8 +87,10 @@ class SGP30
   uint32_t _lastTime = 0;
   uint32_t _lastRequest = 0;
 
+  // TODO improve?
   int      _command(uint16_t cmd);
-  int      _setCommand(uint16_t cmd, uint16_t val);
+  int      _command(uint16_t cmd, uint16_t v1);
+  int      _command(uint16_t cmd, uint16_t v1, uint16_t v2);
   uint8_t  _CRC8(uint16_t val);
   void     _init();
 

examples/SGP30_I2C_performance/SGP30_I2C_performance.ino

@@ -0,0 +1,102 @@
+//
+//    FILE: SGP30_I2C_performance.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo SGP30
+//    DATE: 2021-06-25
+//     URL: https://github.com/RobTillaart/SGP30
+//          https://www.adafruit.com/product/3709
+
+
+#include "SGP30.h"
+
+
+SGP30 SGP;
+
+uint32_t start, stop;
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial) {
+    delay(1);
+    yield();
+  };
+
+  Serial.print(__FILE__);
+  Serial.println(SGP30_LIB_VERSION);
+  Serial.println();
+
+  Serial.print("BEGIN:\t");
+  Serial.println(SGP.begin());
+  Serial.print("TEST:\t");
+  Serial.println(SGP.measureTest());
+
+  delay(1000);
+
+  // has 12 millisecond delay build in...
+  Serial.println("\nMEASURE()");
+  for (uint32_t sp = 100000; sp <= 600000; sp += 50000)
+  {
+    Wire.setClock(sp);
+    start = micros();
+    SGP.measure(false);
+    stop = micros();
+    Serial.print(sp);
+    Serial.print("\t");
+    Serial.println(stop - start);
+    delay(1000);
+  }
+
+  // has 40 millisecond delay build in...
+  Serial.println("\nMEASURE()");
+  for (uint32_t sp = 100000; sp <= 600000; sp += 50000)
+  {
+    Wire.setClock(sp);
+    start = micros();
+    SGP.measure(true);
+    stop = micros();
+    Serial.print(sp);
+    Serial.print("\t");
+    Serial.println(stop - start);
+    delay(1000);
+  }
+
+
+  Serial.println("\nREQUEST()");
+  for (uint32_t sp = 100000; sp <= 600000; sp += 50000)
+  {
+    Wire.setClock(sp);
+    start = micros();
+    SGP.request();
+    stop = micros();
+    Serial.print(sp);
+    Serial.print("\t");
+    Serial.println(stop - start);
+    delay(1000);
+  }
+
+  Serial.println("\nREAD()");
+  for (uint32_t sp = 100000; sp <= 600000; sp += 50000)
+  {
+    Wire.setClock(sp);
+    start = micros();
+    SGP.read();
+    stop = micros();
+    Serial.print(sp);
+    Serial.print("\t");
+    Serial.println(stop - start);
+    SGP.request();
+    delay(1000);
+  }
+
+
+
+}
+
+
+void loop()
+{
+}
+
+
+// -- END OF FILE --