Add DHT20_ERROR_BYTES_ALL_ZERO error message and more (#5)

* fix #4 DHT20_ERROR_BYTES_ALL_ZERO error condition.
* fix keywords
* add readStatus()  fix _readStatus()
* add setWireTimeout(250000, true);  // in comments

DHT20.cpp

@@ -1,18 +1,26 @@
 //
 //    FILE: DHT20.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.1
+// VERSION: 0.1.2
 // PURPOSE: Arduino library for DHT20 I2C temperature and humidity sensor.
 //
 // HISTORY:
 //  0.1.0   2022-01-11  initial version (based upon DHT20 datasheet)
 //  0.1.1   2022-09-10  add hardware schema to readme.md.
 //                      fix async interface (first version)
+//  0.1.2   2022-09-16  fix #4 DHT20_ERROR_BYTES_ALL_ZERO error condition.
+//                      fix keywords
+//                      add readStatus()  fix _readStatus()
+//                      add setWireTimeout(250000, true);  // in comments
 
 
 #include "DHT20.h"
 
-#define DHT20_ACQUISITION_TIME      85
+
+#define DHT20_ACQUISITION_TIME      85        //  milliseconds
+
+//  set DHT20_WIRE_TIME_OUT to 0 to disable.
+#define DHT20_WIRE_TIME_OUT         250000    //  microseconds 
 
 const uint8_t DHT20_ADDRESS = 0x38;
 
@@ -34,6 +42,7 @@ DHT20::DHT20(TwoWire *wire)
 bool DHT20::begin()
 {
   _wire->begin();
+  //  _wire->setWireTimeout(DHT20_WIRE_TIME_OUT, true);
   return isConnected();
 }
 
@@ -47,6 +56,7 @@ bool DHT20::begin(const uint8_t dataPin, const uint8_t clockPin)
   } else {
     _wire->begin();
   }
+  //  _wire->setWireTimeout(DHT20_WIRE_TIME_OUT, true);
   return isConnected();
 }
 #endif
@@ -66,13 +76,17 @@ int DHT20::read()
   //  check lastRead!
   int status = _requestData();
   if (status < 0) return status;
+  //  wait for measurement ready
   while ((millis() - _lastRequest) <= DHT20_ACQUISITION_TIME)
   {
     yield();
     delay(1);
   }
-  _readData();
+  //  read the measurement
+  status = _readData();
+  if (status < 0) return status;
 
+  //  convert it to meaningfull data
   return convert();
 }
 
@@ -129,30 +143,31 @@ int DHT20::_readData()
   if (bytes == 0)     return DHT20_ERROR_CONNECT;
   if (bytes < length) return DHT20_MISSING_BYTES;
 
+  bool allZero = true;
   for (int i = 0; i < bytes; i++)
   {
     _bits[i] = _wire->read();
     //  if (_bits[i] < 0x10) Serial.print(0);
     //  Serial.print(_bits[i], HEX);
     //  Serial.print(" ");
+    allZero = allZero && (_bits[i] == 0);
   }
   //  Serial.println();
+  if (allZero) return DHT20_ERROR_BYTES_ALL_ZERO;
 
   _lastRead = millis();
   return bytes;
 }
 
 
-int DHT20::_readStatus()
+uint8_t DHT20::_readStatus()
 {
-  //  GET CONNECTION
   _wire->beginTransmission(DHT20_ADDRESS);
-  _wire->write(0xAC);
   _wire->write(0x71);
-  _wire->write(0x00);
-  return _wire->endTransmission();
+  _wire->endTransmission();
 
   _wire->requestFrom(DHT20_ADDRESS, (uint8_t)1);
+  return (uint8_t) _wire->read();
 }
 
 

DHT20.h

@@ -3,7 +3,7 @@
 //    FILE: DHT20.h
 //  AUTHOR: Rob Tillaart
 // PURPOSE: Arduino library for DHT20 I2C temperature and humidity sensor.
-// VERSION: 0.1.1
+// VERSION: 0.1.2
 // HISTORY: See DHT20.cpp
 //     URL: https://github.com/RobTillaart/DHT20
 //
@@ -21,12 +21,13 @@
 #include "Arduino.h"
 #include "Wire.h"
 
-#define DHT20_LIB_VERSION                    (F("0.1.1"))
+#define DHT20_LIB_VERSION                    (F("0.1.2"))
 
 #define DHT20_OK                             0
 #define DHT20_ERROR_CHECKSUM                -10
 #define DHT20_ERROR_CONNECT                 -11
 #define DHT20_MISSING_BYTES                 -12
+#define DHT20_ERROR_BYTES_ALL_ZERO          -13
 
 
 #define DHT20_ACQUISITION_TIME               85
@@ -63,6 +64,8 @@ class DHT20
   uint32_t lastRead()       { return _lastRead; };
   uint32_t lastRequest()    { return _lastRequest; };
   int      internalStatus() { return _status; };
+  //  forced read status
+  uint8_t  readStatus()     { return _readStatus(); };
 
 private:
   float    _humidity;
@@ -75,7 +78,7 @@ class DHT20
 
   int      _requestData();
   int      _readData();
-  int      _readStatus();
+  uint8_t  _readStatus();
   uint8_t  _bits[7];
 
   uint8_t  _crc8(uint8_t *ptr, uint8_t len);

README.md

@@ -105,19 +105,28 @@ This can be used to optimize performance a bit. Use with care.
 
 - **uint32_t lastRead()** last time the sensor is read in milliseconds since start.
 - **uint32_t lastRequest()** last time a request is made to make a measurement.
-- **int internalStatus()** returns the internal status of the sensor. (debug ?).
+- **int internalStatus()** returns the internal status of the sensor. (debug ).
+- **uint8_t readStatus()** forced read of the status only.
+
+|  status bit  |  meaning                   |
+|:------------:|:---------------------------|
+|    7         |  busy making measurement   |
+|  6 - 4       |  unknown                   |
+|    3         |  1 = calibrated, 0 is not  |
+|  2 - 0       |  unknown                   |
 
 
 ### Return codes
 
 TODO: fix incomplete list
 
-| name                  |  value  |
-|:----------------------|:-------:|
-| DHT20_OK              |    00   |
-| DHT20_ERROR_CHECKSUM  |   -10   |
-| DHT20_ERROR_CONNECT   |   -11   |
-| DHT20_MISSING_BYTES   |   -12   |
+| name                        |  value  |  notes  |
+|:----------------------------|:-------:|:--------|
+| DHT20_OK                    |    00   |  OK
+| DHT20_ERROR_CHECKSUM        |   -10   |  values might be OK if they are like recent previous ones.
+| DHT20_ERROR_CONNECT         |   -11   |  check connection
+| DHT20_MISSING_BYTES         |   -12   |  check connection
+| DHT20_ERROR_BYTES_ALL_ZERO  |   -13   |  check connection
 
 
 ## Operation
@@ -134,19 +143,21 @@ See examples
   - check return codes etc.
   - add missing error codes
   - **read()** should check lastRead() and return ERROR_LASTREAD
+- add status shortcuts
+  - add **bool isCalibrated()**
+  - add **bool isMeasuring()**
+  - add **bool isIdle()**
+
 
 #### should
 
-- test more in detail
-  - test on ESP32
 - add examples
   - asynchronous
 
 #### could
 
 - improve unit tests.
 - investigate 
-  - status register bits 
   - sensor calibration (website aosong?)
 - check for optimizations.
   - mainly for asynchronous

examples/DHT20/DHT20.ino

@@ -77,6 +77,9 @@ void loop()
       case DHT20_MISSING_BYTES:
         Serial.print("Missing bytes");
         break;
+      case DHT20_ERROR_BYTES_ALL_ZERO:
+        Serial.print("All bytes read zero");
+        break;
       default:
         Serial.print("Unknown error");
         break;

examples/DHT20_plotter/DHT20_plotter.ino

@@ -1,5 +1,5 @@
 //
-//    FILE: DHT20 _plotter.ino
+//    FILE: DHT20_plotter.ino
 //  AUTHOR: Rob Tillaart
 // PURPOSE: Demo for DHT20 I2C humidity & temperature sensor
 //

examples/DHT20_read_status/DHT20_read_status.ino

@@ -0,0 +1,47 @@
+//
+//    FILE: DHT20_read_status.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: Demo for DHT20 I2C humidity & temperature sensor
+//
+
+//  Always check datasheet - front view
+//
+//          +--------------+
+//  VDD ----| 1            |
+//  SDA ----| 2    DHT20   |
+//  GND ----| 3            |
+//  SCL ----| 4            |
+//          +--------------+
+
+
+#include "DHT20.h"
+
+DHT20 DHT;
+
+uint8_t count = 0;
+
+void setup()
+{
+  DHT.begin();    //  ESP32 default pins 21 22
+
+  Wire.setClock(400000);
+
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("DHT20 LIBRARY VERSION: ");
+  Serial.println(DHT20_LIB_VERSION);
+  Serial.println();
+
+  delay(2000);
+}
+
+
+void loop()
+{
+  int status = DHT.readStatus();
+  Serial.println(status);
+  delay(1000);
+}
+
+
+// -- END OF FILE --

examples/DHT20_test_esp/DHT20_test_esp.ino

@@ -57,6 +57,9 @@ void loop()
   case DHT20_MISSING_BYTES:
     Serial.print("Missing bytes,\t");
     break;
+  case DHT20_ERROR_BYTES_ALL_ZERO:
+    Serial.print("All bytes read zero");
+    break;
   default:
     Serial.print("Unknown error,\t");
     break;

keywords.txt

@@ -22,12 +22,16 @@ getTempOffset	KEYWORD2
 
 lastRead	KEYWORD2
 lastRequest	KEYWORD2
-internalStatus()	KEYWORD2
+internalStatus	KEYWORD2
+readStatus	KEYWORD2
 
 
 # Constants (LITERAL1)
 DHT20_LIB_VERSION	LITERAL2
+
 DHT20_OK	LITERAL2
 DHT20_ERROR_CHECKSUM	LITERAL1
 DHT20_ERROR_CONNECT	LITERAL1
 DHT20_MISSING_BYTES	LITERAL1
+DHT20_ERROR_BYTES_ALL_ZERO	LITERAL1
+

library.json

@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/DHT20.git"
   },
-  "version": "0.1.1",
+  "version": "0.1.2",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=DHT20
-version=0.1.1
+version=0.1.2
 author=Rob Tillaart <[email protected]>
 maintainer=Rob Tillaart <[email protected]>
 sentence=Arduino library for I2C DHT20 temperature and humidity sensor. 

test/unit_test_001.cpp

@@ -45,6 +45,7 @@ unittest(test_constants)
   assertEqual(-10, DHT20_ERROR_CHECKSUM);
   assertEqual(-11, DHT20_ERROR_CONNECT);
   assertEqual(-12, DHT20_MISSING_BYTES);
+  assertEqual(-13, DHT20_ERROR_BYTES_ALL_ZERO);
 }
 
 
@@ -58,7 +59,7 @@ unittest(test_constructor)
   assertEqualFloat(0, DHT.getHumOffset(), 0.001);
 
   DHT.begin();
-  assertEqual(DHT20_ERROR_CHECKSUM, DHT.read());
+  assertEqual(DHT20_ERROR_CONNECT, DHT.read());
 
   //  assertEqualFloat(0, DHT.getTemperature(), 0.001);
   //  assertEqualFloat(0, DHT.getHumidity(), 0.001);