0.3.3 MAX6675

Author: RobTillaart

libraries/MAX6675/CHANGELOG.md

@@ -6,6 +6,15 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.3.3] - 2025-03-17
+- add getCelsius() to replace getTemperature() in long term.
+- add getFahrenheit() convenience wrapper.
+- update examples
+- update readme.md
+- update unit test
+- update keywords
+
+
 ## [0.3.2] - 2024-06-03
 - add support for ARDUINO_ARCH_MBED
 

libraries/MAX6675/LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2022-2024 Rob Tillaart
+Copyright (c) 2022-2025 Rob Tillaart
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

libraries/MAX6675/MAX6675.cpp

@@ -1,7 +1,7 @@
 //
 //    FILE: MAX6675.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.3.2
+// VERSION: 0.3.3
 // PURPOSE: Arduino library for MAX6675 chip for K type thermocouple
 //    DATE: 2022-01-11
 //     URL: https://github.com/RobTillaart/MAX6675

libraries/MAX6675/MAX6675.h

@@ -2,7 +2,7 @@
 //
 //    FILE: MAX6675.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.3.2
+// VERSION: 0.3.3
 // PURPOSE: Arduino library for MAX6675 chip for K type thermocouple
 //    DATE: 2022-01-12
 //     URL: https://github.com/RobTillaart/MAX6675
@@ -23,7 +23,7 @@
 #include "SPI.h"
 
 
-#define MAX6675_LIB_VERSION               (F("0.3.2"))
+#define MAX6675_LIB_VERSION               (F("0.3.3"))
 
 
 #ifndef __SPI_CLASS__
@@ -67,11 +67,13 @@ class MAX6675
 
   //       returns state - bit field: 0 = STATUS_OK
   uint8_t  read();
-  float    getTemperature(void)  { return _temperature + _offset; };
+  float    getCelsius(void)      { return _temperature + _offset; };
+  float    getFahrenheit(void)   { return getCelsius() * 1.8 + 32; };
 
   uint8_t  getStatus(void) const { return _status; };
 
   //       use offset to calibrate the TC.
+  //       offset is in degrees Celsius.
   void     setOffset(const float  t)   { _offset = t; };
   float    getOffset() const           { return _offset; };
 
@@ -84,6 +86,8 @@ class MAX6675
   void     setSWSPIdelay(uint16_t del = 0)  { _swSPIdelay = del; };
   uint16_t getSWSPIdelay() { return _swSPIdelay; };
 
+  //  obsolete in future.
+  float    getTemperature(void)  { return _temperature + _offset; };
 
 private:
   uint32_t _read();

libraries/MAX6675/README.md

@@ -17,7 +17,7 @@ The library is based upon (stripped and adapted version of) the https://github.c
 
 Currently the library is experimental, so use with care.
 
-Hardware has finally arrived (April 2022) and I had time to do my first round of tests with an UNO @ 16 MHz. 
+Hardware has finally arrived (April 2022) and I had time to do my first round of tests with an UNO at 16 MHz. 
 The library works and it reads temperatures well, both with HW SPI and SW SPI. 
 
 
@@ -34,7 +34,7 @@ Different TC's have a different Seebeck Coefficient (SC) expressed in µV/°C.
 See http://www.analog.com/library/analogDialogue/archives/44-10/thermocouple.html
 
 
-#### Breakout
+### Breakout
 
 The library is tested with a breakout board with following pins:
 
@@ -49,14 +49,14 @@ The library is tested with a breakout board with following pins:
 ```
 
 
-#### 0.3.0 Breaking change
+### 0.3.0 Breaking change
 
 Version 0.3.0 introduced a breaking change to improve handling the SPI dependency.
 The user has to call **SPI.begin()** or equivalent before calling **AD.begin()**.
 Optionally the user can provide parameters to the **SPI.begin(...)**
 
 
-#### 0.2.0 Breaking change
+### 0.2.0 Breaking change
 
 The version 0.2.0 has breaking changes in the interface. 
 The essence is removal of ESP32 specific code from the library. 
@@ -66,17 +66,18 @@ Also it makes the library a bit simpler to maintain.
 Note the order of the parameters of the software SPI constructor has changed in 0.2.0.
 
 
-#### Related
+### Related
 
-- https://github.com/RobTillaart/MAX6675
+- https://github.com/RobTillaart/MAX6675 
 - https://github.com/RobTillaart/MAX31850
 - https://github.com/RobTillaart/MAX31855_RT
+- https://github.com/RobTillaart/Temperature  conversion to (exotic) temperature scales.
 
 
 ## Hardware SPI vs software SPI
 
 
-#### Pins
+### Pins
 
 Default pin connections.
 
@@ -88,7 +89,7 @@ Default pin connections.
  | SELECT   | eg. 4 |    5        |   15        |  *can be others too.*
 
 
-#### Performance 
+### Performance 
 
 Performance read() function, timing in us.  
 - UNO @ 16 MHz
@@ -117,15 +118,15 @@ Tested with **MAX6675_test_HWSPI.ino**
 #include "MAX6675.h"
 ```
 
-#### Constructor
+### Constructor
 
 - **MAX6675(uint8_t select, SPIClassRP2040 \* mySPI)** hardware SPI R2040
 - **MAX6675(uint8_t select, SPIClass \* mySPI)** hardware SPI other
 - **MAX6675(uint8_t select, uint8_t miso, uint8_t clock)** software SPI
 - **void begin()** initialize internals
 
 
-#### Hardware SPI
+### Hardware SPI
 
 To be used only if one needs a specific speed.
 
@@ -136,63 +137,73 @@ Del is the time in micros added per bit. Even numbers keep the duty cycle of the
 - **uint16_t getSWSPIdelay()** get set value in micros.
 
 
-#### Reading
+### Measurements
+
+- **uint8_t read()** makes a temperature measurement.
+It returns the status of the read (0, 4 or 129)
+- **uint8_t getStatus()** returns the last status value of read().
+Will stay the same until a new **read()** call.
+- **float getTemperature()** returns last temperature in Celsius. (will be obsolete in future).
+- **float getCelsius()** returns last temperature in Celsius. (more explicit scale).
+Will stay the same until a new **read()** call.
+- **float getFahrenheit()** wrapper around getCelsius(). Returns last temperature in Fahrenheit.
+Will stay the same until a new **read()** call.
 
-To make a temperature reading call **read()**.
-It returns the status of the read which is a value between 0..7
-The function **getStatus()** returns the same status value. 
 
 Table: values returned from **uint8_t read()** and **uint8_t getStatus()**
 
 Note: this list is a subset of MAX31855 errors.
 
-| value | Description               | Action       |
-|:-----:|:--------------------------|:-------------|
-|    0  | OK                        |              |
-|    4  | Thermocouple short to VCC | check wiring |
-|  128  | No read done yet          | check wiring |
-|  129  | No communication          | check wiring |
+|  Define                   |  value  |  Description                |  Action        |  Notes  |
+|:--------------------------|:-------:|:----------------------------|:---------------|:--------|
+|  STATUS_OK                |     0   |  OK                         |                |
+|  STATUS_ERROR             |     4   |  Thermocouple short to VCC  |  check wiring  |
+|  STATUS_NOREAD            |   128   |  No read done yet           |  check wiring  |  only before first read()
+|  STATUS_NO_COMMUNICATION  |   129   |  No communication           |  check wiring  |
+
 
+After **uint8_t read()** returns **STATUS_OK** you can get the temperature with 
+**getCelsius()** or **getFahrenheit()**.
 
-After a **uint8_t read()** you can get the temperature with **float getTemperature()**.
+Repeated calls to **getCelsius()** or **getFahrenheit()** will give the same value until a new 
+measurement is made by calling **read()**.
 
-Repeated calls to **getTemperature()** will give the same value until a new **read()**.
-The latter fetches a new value from the sensor. Note that if the **read()** fails
-the value of **getTemperature()** can become incorrect. So it is important to check 
-the return value of **read()**.
+Note: if the **read()** fails the value of **getCelsius()** can become incorrect. 
+So it is important to check the return value of **read()**.
 
 
-#### Offset
+### Offset
 
 The library supports a fixed offset to calibrate the thermocouple.
 For this the functions **float getOffset()** and **void setOffset(float offset)** are available.
-This offset is "added" in the **getTemperature()** function.
+This offset is "added" in the **getCelsius()** function.
 
-Notes
-- the offset can be positive or negative.
+Note:
+- the offset is a constant in degrees Celsius (for Fahrenheit offset multiply by 1.8)
 - the offset used is a float, so decimals can be used.
-A typical usage is to call **setOffset(273.15)** to get ° Kelvin.
-- the offset can cause negative temperatures.
+A typical usage is to call **setOffset(273.15)** to get degrees ° Kelvin.
+- the offset can be positive or negative.
+- the offset can cause negative temperatures to pop up at the lower end.
 
 
-#### Delta analysis
+### Delta analysis
 
 As the **tc** object holds its last known temperature it is easy to determine the delta 
 with the last known temperature, e.g. for trend analysis.
 
 ```cpp
-  float last = tc.getTemperature();
+  float last = tc.getCelsius();
   int state  = tc.read();
   if (state == STATUS_OK)
   {
-    float new  = tc.getTemperature();
+    float new  = tc.getCelsius();
     float delta = new - last;
     // process data
   }
 ```
 
 
-#### Last time read
+### Last time read
 
 The **tc** object keeps track of the last time **read()** is called in the function **uint32_t lastRead()**.
 The time is tracked in **millis()**. This makes it easy to read the sensor at certain intervals.
@@ -203,7 +214,7 @@ if (millis() - tc.lastRead() >= interval)
   int state = tc.read();
   if (state == STATUS_OK)
   {
-    float new = tc.getTemperature();
+    float new = tc.getCelsius();
     // process read value.
   }
   else
@@ -214,7 +225,7 @@ if (millis() - tc.lastRead() >= interval)
 ```
 
 
-#### GetRawData 
+### GetRawData 
 
 The function **uint32_t getRawData()** allows you to get all the 32 bits raw data from the board, 
 after the standard **uint8_t tc.read()** call.

libraries/MAX6675/examples/Demo_getRawData/Demo_getRawData.ino

@@ -18,6 +18,7 @@ MAX6675 thermoCouple(selectPin, dataPin, clockPin);
 
 void setup ()
 {
+  //  while(!Serial);
   Serial.begin(115200);
   Serial.println(__FILE__);
   Serial.print("MAX6675_LIB_VERSION: ");
@@ -43,8 +44,8 @@ void loop ()
   Serial.print("RAW:\t");
 
   //  Display the raw data value in BIN format
-  uint32_t mask = 0x80000000; 
-  for (int i = 0; i < 32; i++) 
+  uint32_t mask = 0x80000000;
+  for (int i = 0; i < 32; i++)
   {
     if ((i > 0)  && (i % 4 == 0)) Serial.print("-");
     Serial.print((value & mask) ? 1 : 0);
@@ -53,7 +54,7 @@ void loop ()
   Serial.println();
 
   Serial.print("TMP:\t");
-  Serial.println(thermoCouple.getTemperature(), 3);
+  Serial.println(thermoCouple.getCelsius(), 3);
 
   delay(100);
 }

libraries/MAX6675/examples/MAX6675_array/MAX6675_array.ino

@@ -22,6 +22,7 @@ uint32_t start, stop;
 
 void setup()
 {
+  //  while(!Serial);
   Serial.begin(115200);
   Serial.println(__FILE__);
   Serial.print("MAX6675_LIB_VERSION: ");
@@ -48,7 +49,7 @@ void loop()
     start = micros();
     int status = ThermoCouples[THCnumber].read();
     stop = micros();
-    float temp = ThermoCouples[THCnumber].getTemperature();
+    float temp = ThermoCouples[THCnumber].getCelsius();
 
     Serial.print(millis());
     Serial.print("\tID: ");

libraries/MAX6675/examples/MAX6675_test/MAX6675_test.ino

@@ -20,6 +20,7 @@ uint32_t start, stop;
 
 void setup()
 {
+  //  while(!Serial);
   Serial.begin(115200);
   Serial.println(__FILE__);
   Serial.print("MAX6675_LIB_VERSION: ");
@@ -40,13 +41,15 @@ void loop()
   start = micros();
   int status = thermoCouple.read();
   stop = micros();
-  float temp = thermoCouple.getTemperature();
+  float temp = thermoCouple.getCelsius();
 
   Serial.print(millis());
   Serial.print("\tstatus: ");
   Serial.print(status);
   Serial.print("\ttemp: ");
   Serial.print(temp);
+  Serial.print("\traw: ");
+  Serial.print(thermoCouple.getRawData(), HEX);
   Serial.print("\tus: ");
   Serial.println(stop - start);
 

libraries/MAX6675/examples/MAX6675_test_HWSPI/MAX6675_test_HWSPI.ino

@@ -17,6 +17,7 @@ uint32_t start, stop;
 
 void setup()
 {
+  //  while(!Serial);
   Serial.begin(115200);
   Serial.println(__FILE__);
   Serial.print("MAX6675_LIB_VERSION: ");
@@ -48,7 +49,7 @@ void testPerformance(uint32_t speed)
   start = micros();
   int status = thermoCouple.read();
   stop = micros();
-  float temp = thermoCouple.getTemperature();
+  float temp = thermoCouple.getCelsius();
 
   Serial.print(millis());
   Serial.print("\tspeed: ");

libraries/MAX6675/examples/MAX6675_test_plotter/MAX6675_test_plotter.ino

@@ -22,6 +22,7 @@ float temp = 0;
 
 void setup()
 {
+  //  while(!Serial);
   Serial.begin(115200);
   //  Serial.println(__FILE__);
   //  Serial.print("MAX6675_LIB_VERSION: ");
@@ -38,7 +39,7 @@ void setup()
 
   int status = thermoCouple.read();
   if (status != 0) Serial.println(status);
-  temp = thermoCouple.getTemperature();
+  temp = thermoCouple.getCelsius();
 }
 
 
@@ -49,7 +50,7 @@ void loop()
   int status = thermoCouple.read();
   stop = micros();
 
-  float newValue = thermoCouple.getTemperature();
+  float newValue = thermoCouple.getCelsius();
   //  0.2 is low pass filter
   temp += 0.2 * (newValue - temp);
   //  temp = newValue;