0.1.3 LTC2485

Author: RobTillaart

libraries/LTC2485/CHANGELOG.md

@@ -6,6 +6,11 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.1.3] - 2025-03-04
+- add simple calibration for temperature
+- add **getLastError()** for minimal error handling
+- extended unit test with constants test
+
 ## [0.1.2] - 2025-02-24
 - add delay() in examples for first conversion (speed dependent)
 - refactor code - several fixes

libraries/LTC2485/LTC2485.cpp

@@ -1,20 +1,31 @@
 //
 //    FILE: LTC2485.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.2
+// VERSION: 0.1.3
 //    DATE: 2025-02-21
 // PURPOSE: Arduino library for LTC2485 I2C 24 bit ADC.
 //     URL: https://github.com/RobTillaart/LTC2485
 
 
 #include "LTC2485.h"
 
+
 //  CONVERSION
 //  needed as I2C is blocked during conversion.
 #define LTC2485_DELAY_1X                        200
 #define LTC2485_DELAY_2X                        100  //  not used yet
 
 
+//  CALIBRATION
+//  adjust these numbers to your need
+//  determine them by averaging multiple TC measurements.
+//  Datasheet page 20: 27 C; 420 mV; 1.40 mV/°C
+//
+const float LTC2485_TAVERAGE       = 27.0;    //  °C
+const float LTC2485_MVOLT_TAVERAGE = 420.0;   //  mV
+const float LTC2485_SLOPE          = 1.40;    //  mV/°C
+
+
 /////////////////////////////////////////////////////
 //
 //  CONSTRUCTORS
@@ -26,7 +37,7 @@ LTC2485::LTC2485(uint8_t address, TwoWire *wire)
   //  defaults
   _lastAccess = 0;
   _timeout    = LTC2485_DELAY_1X;
-  _error      = 0;
+  _error      = LTC2485_OK;
   _vref       = 2.5;
   _config     = LTC2485_SPEED_1X | LTC2485_REJECT_50_60_HZ;
 }
@@ -81,8 +92,7 @@ int32_t LTC2485::getADC()
   {
     if (configure(_config & 0x07) != 0)
     {
-      //  TODO cleaner error handling.
-      Serial.println("FAIL TO CONFIG-A");
+      _error = LTC2485_ERR_CONFIG_ADC;
       return 0;
     }
   }
@@ -113,7 +123,7 @@ float LTC2485::getTemperature()
   {
     if (configure(_config | LTC2485_INTERNAL_TEMP) != 0)
     {
-      Serial.println("FAIL TO CONFIG-T");
+      _error = LTC2485_ERR_CONFIG_TEMP;
       return 0;
     }
   }
@@ -122,20 +132,28 @@ float LTC2485::getTemperature()
   delay(_timeout);
   //  read the ADC
   int32_t value = _read();
+  //  DEBUG
+  //  Serial.print(F("TRAW: \t"));
+  //  Serial.print(value, HEX);
+  //  Serial.print(F("\t"));
+  //  Serial.println(value, DEC);
+
   //  update lastAccess
   _lastAccess = millis();
   //  make two complements.
   value ^= 0x80000000;
   value /= 128;
 
+  //  16777215 == 2^24 - 1
   //  div 16777215 == mul 5.960464832810e-8
   //  float milliVolts = value * _vref * 5.960464832810e-8 * 1000;
   float milliVolts = value * _vref * 5.960464832810e-5;
   _lastAccess = millis();
   //  datasheet page 20
+  //  adjust constants at top of file.
   //  27 C  == 420 mV
   //  SLOPE == 1.40 mV / °C
-  float TC = 27.0 + (milliVolts - 420) / 1.40;
+  float TC = LTC2485_TAVERAGE + (milliVolts - LTC2485_MVOLT_TAVERAGE) / LTC2485_SLOPE;
   return TC;
 }
 
@@ -146,6 +164,19 @@ uint32_t LTC2485::lastAccessed()
 }
 
 
+/////////////////////////////////////////////////////
+//
+//  ERROR HANDLING
+//
+int LTC2485::getLastError()
+{
+  int e = _error;
+  _error = LTC2485_OK;
+  return e;
+}
+
+
+
 //////////////////////////////////////////////////////////////////
 //
 //  PRIVATE functions
@@ -154,49 +185,54 @@ int LTC2485::_write(uint8_t value)
 {
   _wire->beginTransmission(_address);
   _wire->write(value);
-  return _wire->endTransmission();
+  int n = _wire->endTransmission();
+  if (n != 0)
+  {
+    _error = LTC2485_ERR_I2C_W;
+  }
+  return n;
 }
 
 
 uint32_t LTC2485::_read()
 {
-  uint32_t rv = 0;
   int n = _wire->requestFrom(_address, (uint8_t)4);
-  if (n == 4)
+  if (n != 4)
   {
-    rv |= _wire->read();
-    rv <<= 8;
-    rv |= _wire->read();
-    rv <<= 8;
-    rv |= _wire->read();
-    rv <<= 8;
-    rv |= _wire->read();
-    return rv;
-
-    //  DEBUG
-    // uint32_t A = _wire->read();
-    // uint32_t B = _wire->read();
-    // uint32_t C = _wire->read();
-    // uint32_t D = _wire->read();
-    // if (A < 0x10) Serial.print(0);
-    // Serial.print(A, HEX);
-    // Serial.print("\t");
-    // if (B < 0x10) Serial.print(0);
-    // Serial.print(B, HEX);
-    // Serial.print("\t");
-    // if (C < 0x10) Serial.print(0);
-    // Serial.print(C, HEX);
-    // Serial.print("\t");
-    // if (D < 0x10) Serial.print(0);
-    // Serial.print(D, HEX);
-    // Serial.print("\t");
-
-    // rv = (A << 24) + (B << 16) + (C << 8) + D;
-    // return rv;
+    _error = LTC2485_ERR_I2C_R;
+    return n;
   }
-  return n;
-}
+  uint32_t rv = 0;
+  rv |= _wire->read();
+  rv <<= 8;
+  rv |= _wire->read();
+  rv <<= 8;
+  rv |= _wire->read();
+  rv <<= 8;
+  rv |= _wire->read();
+  return rv;
 
+  //  DEBUG
+  //  uint32_t A = _wire->read();
+  //  uint32_t B = _wire->read();
+  //  uint32_t C = _wire->read();
+  //  uint32_t D = _wire->read();
+  //  if (A < 0x10) Serial.print(0);
+  //  Serial.print(A, HEX);
+  //  Serial.print("\t");
+  //  if (B < 0x10) Serial.print(0);
+  //  Serial.print(B, HEX);
+  //  Serial.print("\t");
+  //  if (C < 0x10) Serial.print(0);
+  //  Serial.print(C, HEX);
+  //  Serial.print("\t");
+  //  if (D < 0x10) Serial.print(0);
+  //  Serial.print(D, HEX);
+  //  Serial.print("\t");
+
+  //  rv = (A << 24) + (B << 16) + (C << 8) + D;
+  //  return rv;
+}
 
 
 //  -- END OF FILE --

libraries/LTC2485/LTC2485.h

@@ -2,7 +2,7 @@
 //
 //    FILE: LTC2485.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.2
+// VERSION: 0.1.3
 //    DATE: 2025-02-21
 // PURPOSE: Arduino library for LTC2485 I2C 24 bit ADC.
 //     URL: https://github.com/RobTillaart/LTC2485
@@ -12,7 +12,7 @@
 #include "Wire.h"
 
 
-#define LTC2485_LIB_VERSION               (F("0.1.2"))
+#define LTC2485_LIB_VERSION               (F("0.1.3"))
 
 
 //  CONFIGURATION BITS, TABLE 1
@@ -24,6 +24,14 @@
 #define LTC2485_INTERNAL_TEMP                   0x08
 
 
+//  ERROR
+#define LTC2485_OK                              0
+#define LTC2485_ERR_CONFIG_ADC                  -1
+#define LTC2485_ERR_CONFIG_TEMP                 -2
+#define LTC2485_ERR_I2C_W                       -3
+#define LTC2485_ERR_I2C_R                       -4
+
+
 class LTC2485
 {
 public:
@@ -43,6 +51,8 @@ class LTC2485
 
   uint32_t lastAccessed();
 
+  //  ERROR HANDLING
+  int      getLastError();
 
 private:
 

libraries/LTC2485/README.md

@@ -27,21 +27,27 @@ In practice there will be noise and one need a very stable VREF and test
 setup to get accurate readings on that level.
 
 The LTC2485 has an internal voltage that is proportional to temperature.
-The library allows to read that and has a non calibrated conversion.
+The library allows to read that voltage and converts it to temperature Celsius.
+The formula can be calibrated a bit at the top of the .cpp file.
 
 
 Read the datasheet for the details.
 
 As always, feedback is welcome.
 
+
 ### Tested
 
 Tested with hardware during development.
 More tests are needed to see if and how it can be improved.
 
 See - https://forum.arduino.cc/t/ltc2485-arduino-library/1356147
 
-### Keycode
+At the release 0.1.3 there are still unsolved / unexplained fluctuations 
+visible in the measurements during tests, especially in temperature.
+
+
+### Key code
 
 ALT230 = µ  (windows).
 
@@ -71,13 +77,13 @@ Please use the output of example **LTC2485_performance.ino** and the board used.
 
 ### Compatibles
 
-TODO
+Unknown so far, there exists a whole range of LTCxxxx ADC's.
 
 
 ### Related
 
 - https://gammon.com.au/adc  tutorial about ADC's (UNO specific)
-- https://github.com/RobTillaart/LTC2485
+- https://github.com/RobTillaart/LTC2485  this library
 - https://github.com/RobTillaart/MCP_ADC  SPI based ADC
 - https://github.com/RobTillaart/ADS1x15  (12 & 16 bit ADC, I2C, slow)
 - https://github.com/RobTillaart/PCF8591  (8 bit ADC + 1 bit DAC)
@@ -106,7 +112,7 @@ Note: do call **Wire.begin()** before **begin()**
 ### Configure
 
 - **int configure(uint8_t value)** set flags for next conversion.
-Returns status of I2C, 0 == success write.
+Returns status of I2C, 0 == success write, other values == error.
 
 Configuration bit masks, should be OR-ed.
 
@@ -119,7 +125,8 @@ Configuration bit masks, should be OR-ed.
 |  LTC2485_REJECT_60HZ      |  0x04   |
 |  LTC2485_INTERNAL_TEMP    |  0x08   |
 
-LTC2485_REJECT_50HZ and LTC2485_REJECT_50HZ may **NOT** be set simultaneously.
+Flags LTC2485_REJECT_50HZ and LTC2485_REJECT_60HZ may **NOT** be used simultaneously.
+Use LTC2485_REJECT_50_60_HZ instead.
 
 example
 
@@ -133,14 +140,19 @@ LTC.configure(LTC2485_SPEED_2X | LTC2485_REJECT_60HZ);
 Read returns the last conversion and triggers a new conversion at the end.
 So it might be needed to discard a first read.
 
-- **int32_t getADC()** returns ADC value. Will configure ADC mode automatically.
-Returned range == -16777215..+16777215
+- **int32_t getADC()** returns ADC value. Will configure ADC mode automatically
+if needed. 
+Returned range == -16777215..+16777215  
++16777216 == overflow  
+-16777216 == underflow
 - **float getVolts()** converts ADC value to volts.
 - **float getMilliVolts()** converts ADC value to millivolts.
 - **float getMicroVolts()** converts ADC value to microvolts.
 - **float getTemperature()** returns internal temperature.
 Will configure temperature mode automatically.
-
+During first hardware tests it was impossible to get the temperature
+stable. 
+This needs more investigation in the future.
 - **uint32_t lastAccesed()** track time in milliseconds of last access.
 used internally to determine maximum delay needed for conversion.
 
@@ -154,29 +166,26 @@ used internally to determine maximum delay needed for conversion.
   - compatibles section
 - get hardware to test library
 
-
 #### Should
 
-- fix TODO's in code and documentation.
-- check pin compatible devices as derived class?
-  - LTC2481 (16 bits) and LTC2483 (16 bits)
-- improve error handling.
+- improve error handling
   - overflow / underflow
   - time out handling?
-- performance measurements
-  - I2C bus speed?
-  - check math for improvements
-- refactor for performance.
-
+- fix TODO's in code and documentation
 
 #### Could
 
+- check pin compatible devices as derived class?
+  - LTC2481 (16 bits) and LTC2483 (16 bits)
 - calibrate internal temperature, something like
   - **void calibrateTemperature(float A, float B)**  420.0  1.40
   - TC = 27 + (Voltage - A) x B;
 - create a 16 bit API which only gets 2 bytes instead of 4?
   - looses the "noisy" bits.
-
+- performance measurements
+  - I2C bus speed?
+  - check math for improvements
+- refactor for performance
 
 #### Wont
 

libraries/LTC2485/examples/LTC2485_connect/LTC2485_connect.ino

@@ -11,9 +11,9 @@
 
 //  adjust address if needed
 //  0x14  CA1 = LOW  CA0 = HIGH
-LTC2485 LTC(0x14);
+LTC2485 LTC(0x16);
 
-float VREF = 5.0;
+float VREF = 1.8;
 
 void setup()
 {