sync DS18B20_RT (#21)

- sync DS18B20_RT  (GND error)

Author: RobTillaart

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.3.5] - 2026-01-24
+- sync DS18B20_RT  (GND error)
+
 ## [0.3.4] - 2026-01-02
 - update GitHub actions
 - update examples

README.md

@@ -187,6 +187,38 @@ Note: thicker wires require smaller resistors (typically 1 step in E12 series)
 \* = no info, smaller?
 
 
+### Diagnostic notes
+
+It was noted that the library sometimes give unexpected values, and keep 
+sending these values.
+
+This is due to the fact that by default the CRC is not checked to speed up reading. 
+In fact, only the two temperature registers are read.
+
+Table of known "strange values" and actions one could take.
+It is meant to start some diagnosis.
+
+(note these are all known errors, not perse for this library)
+
+| value   | possible cause                      |  optional action  |
+|:--------|:------------------------------------|:------------------|
+|  0.0000 | data line has no pull up            |  use pull up
+| -0.0625 | data line is constantly pulled HIGH |  check GND
+| -127    | DISCONNECTED                        |  check wires
+| -128    | CRC error                           |  wrong pull up, bad sensor ? | 
+| -129    | POR error                           |  no convert done after power up. redo convert call.
+| -130    | GND error                           |  if parasitic mode, check Vdd must be connected to GND.
+
+If a value occurs only once in a while, wiring is often the cause, 
+or it can be caused by e.g. induction e.g. switching on a motor while 
+sensor is read.
+
+Additional notes:
+
+- https://github.com/milesburton/Arduino-Temperature-Control-Library/pull/289
+
+
+
 ## Performance
 
 To elaborate connected state.

examples/DS18B20_performance/DS18B20_performance.ino

@@ -1,7 +1,7 @@
 //
 //    FILE: DS18B20_performance.ino
 //  AUTHOR: Rob Tillaart
-// PURPOSE: DS18B20 lib getAddress demo
+// PURPOSE: measure performance
 //     URL: https://github.com/RobTillaart/DS18B20_INT
 
 

library.json

@@ -23,7 +23,7 @@
       "version": "^2.3.5"
     }
   ],
-  "version": "0.3.4",
+  "version": "0.3.5",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",

library.properties

@@ -1,5 +1,5 @@
 name=DS18B20_int
-version=0.3.4
+version=0.3.5
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Library for DS18B20 restricted to a single sensor per pin.

src/DS18B20_INT.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: DS18B20_INT.cpp
 //  AUTHOR: Rob.Tillaart
-// VERSION: 0.3.4
+// VERSION: 0.3.5
 //    DATE: 2017-07-25
 // PURPOSE: library for DS18B20 temperature sensor - integer only.
 //     URL: https://github.com/RobTillaart/DS18B20_INT
@@ -51,8 +51,8 @@ bool DS18B20_INT::isConnected(uint8_t retries)
     _oneWire->reset_search();
     _deviceAddress[0] = 0x00;
     _oneWire->search(_deviceAddress);
-    _addressFound = _deviceAddress[0] != 0x00 &&
-                _oneWire->crc8(_deviceAddress, 7) == _deviceAddress[7];
+    _addressFound = (_deviceAddress[0] != 0x00) &&
+                (_oneWire->crc8(_deviceAddress, 7) == _deviceAddress[7]);
   }
   return _addressFound;
 }
@@ -85,16 +85,25 @@ bool DS18B20_INT::isConversionComplete(void)
 }
 
 
-int16_t DS18B20_INT::getTempC(bool connectCheck)
+int16_t DS18B20_INT::getTempC(bool checkConnect)
 {
-  if (connectCheck)
+  ScratchPad scratchPad;
+  if (checkConnect)
   {
     if (isConnected(3) == false)
     {
       return DEVICE_DISCONNECTED;
     }
   }
-  int16_t rawTemperature = _readRaw();
+  readScratchPad(scratchPad, 2);
+  //  Power On Reset 85C error cannot be tested here
+  //  the 127.94 error can be checked here
+  if ((scratchPad[1] == 0x07) && (scratchPad[0] == 0xFF))
+  {
+    return DEVICE_GND_ERROR;
+  }
+
+  int16_t rawTemperature = (((int16_t)scratchPad[1]) << 8) | scratchPad[0];
   rawTemperature >>= 4;
   if (rawTemperature < -55)
   {
@@ -123,18 +132,26 @@ uint8_t DS18B20_INT::getResolution()
 
 int16_t DS18B20_INT::getTempCentiC(void)
 {
+  ScratchPad scratchPad;
   if (isConnected(3) == false)
   {
-    return DEVICE_DISCONNECTED;
+    return DEVICE_DISCONNECTED * 100;
+  }
+  readScratchPad(scratchPad, 2);
+  //  Power On Reset 85C error cannot be tested here
+  //  the 127.94 error can be checked here
+  if ((scratchPad[1] == 0x07) && (scratchPad[0] == 0xFF))
+  {
+    return DEVICE_GND_ERROR * 100;
   }
-  int16_t rawTemperature = _readRaw();
+  int16_t rawTemperature = (((int16_t)scratchPad[1]) << 8) | scratchPad[0];
   //  rawTemperature = rawTemperature * 100 / 16;
   rawTemperature *= 25;
-  rawTemperature >>= 2;
+  rawTemperature >>= 4;
   //  use at own risk. (not tested)
   if (rawTemperature < -5500)
   {
-    return DEVICE_DISCONNECTED * 100;
+    return DEVICE_DISCONNECTED;
   }
   return rawTemperature;
 }
@@ -144,16 +161,17 @@ int16_t DS18B20_INT::getTempCentiC(void)
 //
 //  PRIVATE
 //
-int16_t DS18B20_INT::_readRaw(void)
+void DS18B20_INT::readScratchPad(uint8_t *scratchPad, uint8_t fields)
 {
   _oneWire->reset();
   _oneWire->select(_deviceAddress);
   _oneWire->write(READSCRATCH);
 
-  int16_t rawTemperature = ((int16_t)_oneWire->read());
-  rawTemperature |= _oneWire->read() << 8;
+  for (uint8_t i = 0; i < fields; i++)
+  {
+    scratchPad[i] = _oneWire->read();
+  }
   _oneWire->reset();
-  return rawTemperature;
 }
 
 

src/DS18B20_INT.h

@@ -2,7 +2,7 @@
 //
 //    FILE: DS18B20_INT.h
 //  AUTHOR: Rob.Tillaart
-// VERSION: 0.3.4
+// VERSION: 0.3.5
 //    DATE: 2017-07-25
 // PURPOSE: Minimalistic library for DS18B20 temperature sensor
 //          uses only integer math (no float to minimize footprint)
@@ -25,13 +25,17 @@
 #include "OneWire.h"
 
 
-#define DS18B20_INT_LIB_VERSION       (F("0.3.4"))
+#define DS18B20_INT_LIB_VERSION       (F("0.3.5"))
 
-//  Error Code
-#define DEVICE_DISCONNECTED           -127
+//  Error Codes (not all used)
+const int DEVICE_DISCONNECTED = -127;
+const int DEVICE_CRC_ERROR    = -128;
+const int DEVICE_POR_ERROR    = -129;
+const int DEVICE_GND_ERROR    = -130;  //  parasitic power Vdd must GND
 
 
 typedef uint8_t DeviceAddress[8];
+typedef uint8_t ScratchPad[9];
 
 
 class DS18B20_INT
@@ -43,9 +47,10 @@ class DS18B20_INT
   bool      getAddress(uint8_t * buf);
 
   void      requestTemperatures(void);
-  int16_t   getTempC(bool connectCheck = true);
+  int16_t   getTempC(bool checkConnect = true);
   bool      isConversionComplete(void);
 
+  //  for getTempCentiC()
   bool      setResolution(uint8_t resolution = 9);
   uint8_t   getResolution();  //  returns cached value
 
@@ -58,7 +63,7 @@ class DS18B20_INT
   bool          _addressFound;
 
   uint8_t       _resolution;
-  int16_t       _readRaw();
+  void          readScratchPad(uint8_t *scratchPad, uint8_t fields);
   void          _setResolution();
 };