diff --git a/libraries/MAX31855_RT/.arduino-ci.yml b/libraries/MAX31855_RT/.arduino-ci.yml
index cecf5850..25980972 100644
--- a/libraries/MAX31855_RT/.arduino-ci.yml
+++ b/libraries/MAX31855_RT/.arduino-ci.yml
@@ -1,3 +1,18 @@
+platforms:
+  rpipico:
+    board: rp2040:rp2040:rpipico
+    package: rp2040:rp2040
+    gcc:
+      features:
+      defines:
+        - ARDUINO_ARCH_RP2040
+      warnings:
+      flags:
+
+packages:
+  rp2040:rp2040:
+    url: https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
+
 compile:
   # Choosing to run compilation tests on 2 different Arduino platforms
   platforms:
@@ -9,3 +24,4 @@ compile:
     - esp32
     # - esp8266
     # - mega2560
+    - rpipico
diff --git a/libraries/MAX31855_RT/CHANGELOG.md b/libraries/MAX31855_RT/CHANGELOG.md
new file mode 100644
index 00000000..d58ab831
--- /dev/null
+++ b/libraries/MAX31855_RT/CHANGELOG.md
@@ -0,0 +1,90 @@
+# Change Log MAX31855_RT
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+
+## [0.4.2] - 2022-11-16
+- add RP2040 in build-CI
+- add changelog.md
+- minor edit readme.md
+- minor edit unit test
+
+
+## [0.4.1] - 2021-12-10
+- add SWSPI delay + getter/setter
+
+## [0.4.0] - 2021-12-09  
+- fix #21 breaking change for HW SPI
+- move constructor code to begin()
+- read() removed "premature" return on status.
+
+----
+
+## [0.3.0] - 2021-08-11
+- VSPI / HSPI support for ESP32
+- add setGIOpins - ESP32 specific
+- add get/setSPIspeed() - all
+
+## [0.2.5] - 2021-07-04
+- fix #14 CS for STM32.
+
+## [0.2.4] - 2020-12-30
+- arduinoCI, unit test
+
+## [0.2.3] - 2020-08-30
+- fix #8 support hardware SPI + example
+
+## [0.2.2] - 2020-08-30
+- fix #9
+- fix failing examples
+- minor refactor
+
+## [0.2.1] - 2020-08-26
+- read rawData and STATUS_NO_COMMUNICATION recognition (thanks to FabioBrondo)
+
+## [0.2.0] - 2020-06-20
+- add #pragma once
+- major refactor
+- remove pre 1.0 support
+- fix offset
+
+----
+
+## [0.1.10] - 2019-07-31
+- add 3 inline functions to test errors
+- add demo sketch
+
+## [0.1.9] - 2017-07-27
+- fix #33 reverted double -> float
+
+## [0.1.08] - 2015-12-06
+- replaced all temperature calls with one TCfactor
+- update demos.
+
+## [0.1.07] - 2015-12-06
+- updated TC factors from the MAX31855 datasheet
+
+## [0.1.06] - 2015-12-05
+- added support for other types of TC's (experimental)
+
+## [0.1.05] - 2015-07-12
+- refactor robust constructor.
+
+## [0.1.04] - 2015-03-09
+- replaced float -> double (ARM support).
+
+## [0.1.03] - 2014-01-24
+- fixed negative temperature.
+
+## [0.1.02] - 2014-01-03
+- added offset.
+
+## [0.1.01] - 2014-01-02
+- refactored speed/performance.
+
+## [0.1.00] - 2014-01-02
+- initial version.
+
diff --git a/libraries/MAX31855_RT/MAX31855.cpp b/libraries/MAX31855_RT/MAX31855.cpp
index bf3cadf4..0059c587 100644
--- a/libraries/MAX31855_RT/MAX31855.cpp
+++ b/libraries/MAX31855_RT/MAX31855.cpp
@@ -1,37 +1,12 @@
 //
 //    FILE: MAX31855.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.1
+// VERSION: 0.4.2
 // PURPOSE: Arduino library for MAX31855 chip for K type thermocouple
 //    DATE: 2014-01-01
 //     URL: https://github.com/RobTillaart/MAX31855_RT
 //
-//  HISTORY:
-//  0.4.1   2021-12-10  add SWSPI delay + getter/setter
-//  0.4.0   2021-12-09  fix #21 breaking change for HW SPI
-//                      move constructor code to begin()
-//                      read() removed "premature" return on status.
-//  0.3.0   2021-08-11  VSPI / HSPI support for ESP32
-//                      add setGIOpins - ESP32 specific
-//                      add get/setSPIspeed() - all
-//  0.2.5   2021-07-04  fix #14 CS for STM32
-//  0.2.4   2020-12-30  arduinoCI, unit test
-//  0.2.3   2020-08-30  fix #8 support hardware SPI + example
-//  0.2.2   2020-08-30  fix#9 + fix failing examples + minor refactor
-//  0.2.1   2020-08-26  read rawData and STATUS_NO_COMMUNICATION recognition (thanks to FabioBrondo)
-//  0.2.0   2020-06-20  #pragma once; major refactor; removed pre 1.0 support; fix offset
-//  0.1.10  2019-07-31  add 3 inline functions to test errors + demo sketch
-//  0.1.9   2017-07-27  reverted double -> float (issue33)
-//  0.1.08  2015-12-06  replaced all temperature calls with one TCfactor + update demos.
-//  0.1.07  2015-12-06  updated TC factors from the MAX31855 datasheet
-//  0.1.06  2015-12-05  added support for other types of TC's (experimental)
-//  0.1.05  2015-07-12  refactor robust constructor
-//  0.1.04  2015-03-09  replaced float -> double (ARM support)
-//  0.1.03  2014-01-24  fixed negative temperature
-//  0.1.02  2014-01-03  added offset
-//  0.1.01  2014-01-02  refactored speed/performance
-//  0.1.00  2014-01-02  initial version.
-//
+// HISTORY: see changelog.md
 
 
 #include "MAX31855.h"
@@ -70,19 +45,19 @@ void MAX31855::begin(const uint8_t clock, const uint8_t select, const uint8_t mi
   if (_hwSPI)
   {
     #if defined(ESP32)
-    if (_useHSPI)      // HSPI
+    if (_useHSPI)      //  HSPI
     {
       mySPI = new SPIClass(HSPI);
       mySPI->end();
-      mySPI->begin(14, 12, 13, _select);   // CLK=14 MISO=12 MOSI=13
+      mySPI->begin(14, 12, 13, _select);   //  CLK=14  MISO=12  MOSI=13
     }
-    else               // VSPI
+    else               //  VSPI
     {
       mySPI = new SPIClass(VSPI);
       mySPI->end();
-      mySPI->begin(18, 19, 23, _select);   // CLK=18 MISO=19 MOSI=23
+      mySPI->begin(18, 19, 23, _select);   //  CLK=18  MISO=19  MOSI=23
     }
-    #else              // generic hardware SPI
+    #else              //  generic hardware SPI
     mySPI = &SPI;
     mySPI->end();
     mySPI->begin();
@@ -123,21 +98,21 @@ void MAX31855::setGPIOpins(uint8_t clock, uint8_t miso, uint8_t mosi, uint8_t se
 
 uint8_t MAX31855::read()
 {
-  // return value of _read()
-  // BITS     DESCRIPTION
-  // ----------------------
-  // 00 - 02  STATUS
-  //      03  RESERVED
-  // 04 - 15  INTERNAL
-  //      16  FAULT-BIT
-  //      17  RESERVED
-  // 18 - 30  TEMPERATURE (RAW)
-  //      31  SIGN
+  //  return value of _read()
+  //  BITS        DESCRIPTION
+  //  -------------------------------
+  //  00 - 02     STATUS
+  //       03     RESERVED
+  //  04 - 15     INTERNAL
+  //       16     FAULT-BIT
+  //       17     RESERVED
+  //  18 - 30     TEMPERATURE (RAW)
+  //       31     SIGN
   uint32_t value = _read();
 
-  if (value == 0xFFFFFFFF)  // needs a pull up on MISO pin to work properly!
+  if (value == 0xFFFFFFFF)  //  needs a pull up on MISO pin to work properly!
   {
-    // bit 3 and bit 17 should always be 0 - P10 datasheet
+    //  bit 3 and bit 17 should always be 0 - P10 datasheet
     _status = STATUS_NO_COMMUNICATION;
     return _status;
   }
@@ -146,35 +121,35 @@ uint8_t MAX31855::read()
 
   //  process status bit 0-2
   _status = value & 0x0007;
-  // if (_status != STATUS_OK)  // removed in 0.4.0 as internal can be valid.
+  // if (_status != STATUS_OK)  //  removed in 0.4.0 as internal can be valid.
   // {
   //   return _status;
   // }
 
   value >>= 3;
 
-  // reserved bit 3, always 0
+  //  reserved bit 3, always 0
   value >>= 1;
 
-  // process internal bit 4-15
+  //  process internal bit 4-15
   _internal = (value & 0x07FF) * 0.0625;
-  // negative flag set ?
+  //  negative flag set ?
   if (value & 0x0800)
   {
     _internal = -128 + _internal;
   }
   value >>= 12;
 
-  // Fault bit ignored as we have the 3 status bits
-  // _fault = value & 0x01;
+  //  Fault bit ignored as we have the 3 status bits
+  //  _fault = value & 0x01;
   value >>= 1;
 
-  // reserved bit 17, always 0
+  //  reserved bit 17, always 0
   value >>= 1;
 
-  // process temperature bit 18-30 + sign bit = 31
+  //  process temperature bit 18-30 + sign bit = 31
   _temperature = (value & 0x1FFF) * 0.25;
-  // negative flag set ?
+  //  negative flag set ?
   if (value & 0x2000)
   {
     _temperature = -2048 + _temperature;
@@ -186,7 +161,7 @@ uint8_t MAX31855::read()
 uint32_t MAX31855::_read(void)
 {
   _rawData = 0;
-  // DATA TRANSFER
+  //  DATA TRANSFER
   if (_hwSPI)
   {
     mySPI->beginTransaction(_spi_settings);
@@ -199,10 +174,10 @@ uint32_t MAX31855::_read(void)
     digitalWrite(_select, HIGH);
     mySPI->endTransaction();
   }
-  else  // Software SPI
+  else  //  Software SPI
   {
-    // split _swSPIdelay in equal dLow and dHigh
-    // dLow should be longer one when _swSPIdelay = odd.
+    //  split _swSPIdelay in equal dLow and dHigh
+    //  dLow should be longer one when _swSPIdelay = odd.
     uint16_t dHigh = _swSPIdelay/2;
     uint16_t dLow = _swSPIdelay - dHigh;
     digitalWrite(_select, LOW);
@@ -210,10 +185,10 @@ uint32_t MAX31855::_read(void)
     {
       _rawData <<= 1;
       digitalWrite(_clock, LOW);
-      if (dLow > 0) delayMicroseconds(dLow);  // DUE might need 1 us
+      if (dLow > 0) delayMicroseconds(dLow);    //  DUE might need 1 us
       if ( digitalRead(_miso) ) _rawData++;
       digitalWrite(_clock, HIGH);
-      if (dHigh > 0) delayMicroseconds(dHigh);  // DUE
+      if (dHigh > 0) delayMicroseconds(dHigh);  //  DUE
     }
     digitalWrite(_select, HIGH);
   }
@@ -224,18 +199,18 @@ uint32_t MAX31855::_read(void)
 
 float MAX31855::getTemperature()
 {
-  // offset needs to be added after multiplication TCfactor
-  // not before otherwise offset will be larger / smaller
-  // default behaviour
+  //  offset needs to be added after multiplication TCfactor
+  //  not before otherwise offset will be larger / smaller
+  //  default behaviour
   if (_SeebeckC == K_TC) return _temperature + _offset;
 
-  // EXPERIMENTAL OTHER THERMOCOUPLES
-  // to be tested
-  // in practice this works also for K_TC but is way slower..
-  // 1: reverse calculate the Voltage measured  (is this correct?)
-  float Vout = K_TC * (_temperature - _internal);  // PAGE 8 datasheet
+  //  EXPERIMENTAL OTHER THERMOCOUPLES
+  //  to be tested
+  //  in practice this works also for K_TC but is way slower..
+  //  1: reverse calculate the Voltage measured  (is this correct?)
+  float Vout = K_TC * (_temperature - _internal);  //  PAGE 8 datasheet
 
-  // 2: from Voltage to corrected temperature using the Seebeck Coefficient
+  //  2: from Voltage to corrected temperature using the Seebeck Coefficient
   float _temp = Vout / _SeebeckC + _internal + _offset;
   return _temp;
 }
diff --git a/libraries/MAX31855_RT/MAX31855.h b/libraries/MAX31855_RT/MAX31855.h
index 178ec607..6413e0e1 100644
--- a/libraries/MAX31855_RT/MAX31855.h
+++ b/libraries/MAX31855_RT/MAX31855.h
@@ -2,30 +2,30 @@
 //
 //    FILE: MAX31855.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.4.1
+// VERSION: 0.4.2
 // PURPOSE: Arduino library for MAX31855 chip for K type thermocouple
 //    DATE: 2014-01-01
 //     URL: https://github.com/RobTillaart/MAX31855_RT
 //          http://forum.arduino.cc/index.php?topic=208061
 
 
-// Breakout board
+//        Breakout board
 //
-//     +---------+
-// Vin | o       |
-// 3V3 | o       |
-// GND | o     O | Thermocouple
-//  D0 | o     O | Thermocouple
-//  CS | o       |
-// CLK | o       |
-//     +---------+
+//         +---------+
+//     Vin | o       |
+//     3V3 | o       |
+//     GND | o     O |   Thermocouple
+//      D0 | o     O |   Thermocouple
+//      CS | o       |
+//     CLK | o       |
+//         +---------+
 
 
 #include "Arduino.h"
 #include "SPI.h"
 
 
-#define MAX31855_VERSION              (F("0.4.1"))
+#define MAX31855_VERSION              (F("0.4.2"))
 
 #define MAX31855_NO_TEMPERATURE       -999
 
@@ -71,7 +71,7 @@ public:
   //  SW SPI
   void     begin(uint8_t clock, uint8_t select, uint8_t miso);
 
-  // returns state - bit field: 0 = STATUS_OK
+  //  returns state - bit field: 0 = STATUS_OK
   uint8_t  read();
 
   float    getInternal(void) const { return _internal; }
@@ -85,7 +85,7 @@ public:
   inline   bool noRead()          { return _status == STATUS_NOREAD; };
   inline   bool noCommunication() { return _status == STATUS_NO_COMMUNICATION; };
 
-  // use offset to calibrate the TC.
+  //  use offset to calibrate the TC.
   void     setOffset(const float  t)   { _offset = t; };
   float    getOffset() const           { return _offset; };
 
@@ -112,7 +112,7 @@ public:
   bool     usesHSPI()   { return _useHSPI;  };
   bool     usesVSPI()   { return !_useHSPI; };
 
-  // to overrule ESP32 default hardware pins
+  //  to overrule ESP32 default hardware pins
   void     setGPIOpins(uint8_t clock, uint8_t miso, uint8_t mosi, uint8_t select);
   #endif
 
diff --git a/libraries/MAX31855_RT/README.md b/libraries/MAX31855_RT/README.md
index 6d898f6b..938d2a77 100644
--- a/libraries/MAX31855_RT/README.md
+++ b/libraries/MAX31855_RT/README.md
@@ -27,14 +27,14 @@ other types of TC's. See details below.
 Library tested with breakout board
 
 ```
-     +---------+
- Vin | o       |
- 3V3 | o       |
- GND | o     O | Thermocouple
-  D0 | o     O | Thermocouple
-  CS | o       |
- CLK | o       |
-     +---------+
+         +---------+
+     Vin | o       |
+     3V3 | o       |
+     GND | o     O | Thermocouple
+      D0 | o     O | Thermocouple
+      CS | o       |
+     CLK | o       |
+         +---------+
 
 ```
 
@@ -62,7 +62,6 @@ Performance read() function, timing in us.  (ESP32 @240MHz)
 | SW SPI | bit bang |    ~500    |      ~17 (!) |
 
 
-
 ## Interface
 
 
@@ -286,6 +285,13 @@ as one does not set the Seebeck Coefficient it will use the K_TC as default.
 
 ## Future
 
+#### must
+
+
+#### should
 - investigate other TC's 
 - 
 
+
+#### could
+
diff --git a/libraries/MAX31855_RT/library.json b/libraries/MAX31855_RT/library.json
index 89b1febc..8f8e58c9 100644
--- a/libraries/MAX31855_RT/library.json
+++ b/libraries/MAX31855_RT/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/MAX31855_RT"
   },
-  "version": "0.4.1",
+  "version": "0.4.2",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",
diff --git a/libraries/MAX31855_RT/library.properties b/libraries/MAX31855_RT/library.properties
index 4c9ecd8c..449dc8db 100644
--- a/libraries/MAX31855_RT/library.properties
+++ b/libraries/MAX31855_RT/library.properties
@@ -1,5 +1,5 @@
 name=MAX31855_RT
-version=0.4.1
+version=0.4.2
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for MAX31855 chip for K type thermocouple.
diff --git a/libraries/MAX31855_RT/test/unit_test_001.cpp b/libraries/MAX31855_RT/test/unit_test_001.cpp
index 18f2de05..938b315b 100644
--- a/libraries/MAX31855_RT/test/unit_test_001.cpp
+++ b/libraries/MAX31855_RT/test/unit_test_001.cpp
@@ -36,32 +36,19 @@
 #include "MAX31855.h"
 
 
-
 unittest_setup()
 {
+  fprintf(stderr, "MAX31855_VERSION: %s\n", (char *) MAX31855_VERSION);
 }
 
+
 unittest_teardown()
 {
 }
 
-/*
-unittest(test_new_operator)
-{
-  assertEqualINF(exp(800));
-  assertEqualINF(0.0/0.0);
-  assertEqualINF(42);
-  
-  assertEqualNAN(INFINITY - INFINITY);
-  assertEqualNAN(0.0/0.0);
-  assertEqualNAN(42);
-}
-*/
 
 unittest(test_constants)
 {
-  fprintf(stderr, "MAX31855_VERSION: %s\n", (char *) MAX31855_VERSION);
-
   assertEqual(0x00, STATUS_OK);
   assertEqual(0x01, STATUS_OPEN_CIRCUIT);
   assertEqual(0x02, STATUS_SHORT_TO_GND);
@@ -69,15 +56,13 @@ unittest(test_constants)
   assertEqual(0x07, STATUS_ERROR);
   assertEqual(0x80, STATUS_NOREAD);
   assertEqual(0x81, STATUS_NO_COMMUNICATION);
-  
+
   assertEqual(-999, MAX31855_NO_TEMPERATURE);
 }
 
 
 unittest(test_status)
 {
-  fprintf(stderr, "MAX31855_VERSION: %s\n", (char *) MAX31855_VERSION);
-  
   const int doPin = 7;
   const int csPin = 6;
   const int clPin = 5;
@@ -100,8 +85,6 @@ unittest(test_status)
 
 unittest(test_temperature)
 {
-  fprintf(stderr, "MAX31855_VERSION: %s\n", (char *) MAX31855_VERSION);
-  
   const int doPin = 7;
   const int csPin = 6;
   const int clPin = 5;
@@ -122,7 +105,7 @@ unittest(test_temperature)
   }
 
   fprintf(stderr, "\nSeebeckCoefficient...\n");
-  for (float sbc = 9; sbc < 100; sbc += 12.345)  // non existent still good for test.
+  for (float sbc = 9; sbc < 100; sbc += 12.345)    //  non existent still good for test.
   {
     tc.setSeebeckCoefficient(sbc);
     fprintf(stderr, "%f\t", sbc);
@@ -133,8 +116,6 @@ unittest(test_temperature)
 
 unittest(test_SPIspeed_SWSPIdelay)
 {
-  fprintf(stderr, "MAX31855_VERSION: %s\n", (char *) MAX31855_VERSION);
-  
   const int doPin = 7;
   const int csPin = 6;
   const int clPin = 5;
@@ -162,4 +143,5 @@ unittest(test_SPIspeed_SWSPIdelay)
 
 unittest_main()
 
-// --------
+
+//  -- END OF FILE --