diff --git a/.arduino-ci.yml b/.arduino-ci.yml
index b3e33db..572b108 100644
--- a/.arduino-ci.yml
+++ b/.arduino-ci.yml
@@ -1,14 +1,30 @@
+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:
     - uno
-    - due
-    - zero
-    - leonardo
+    # - due
+    # - zero
+    # - leonardo
     - m4
     - esp32
     - esp8266
-    - mega2560
+    # - mega2560
+    - rpipico
   libraries:
     - "printHelpers"
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..4aa8211
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,38 @@
+# Change Log timing
+
+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/).
+
+
+## [0.2.4] - 2022-11-26
+- Add RP2040 support to build-CI.
+- Add CHANGELOG.md
+- update readme.md
+
+
+## [0.2.3] - 2021-12-29
+- update library.json
+- update license
+- minor edits
+
+## [0.2.2] - 2021-05-27
+- added Arduino-lint
+
+## [0.2.1] - 2021-01-09
+- added Arduino-CI + unit test
+
+## [0.2.0] - 2020-07-07
+- renamed to timing.h
+
+----
+
+## [0.1.02] - 2015-03-02
+- move all to mymillis.h file so compiler can optimize
+
+## [0.1.01] - 2011-07-19
+- add lib version
+
+## [0.1.00] - 2011-01-04
+- initial version
diff --git a/README.md b/README.md
index c81687a..06e1fae 100644
--- a/README.md
+++ b/README.md
@@ -24,11 +24,11 @@ Therefore they have the same restrictions as these functions with respect to
 overflow and accuracy. Depending on e.g. interrupts millis and micros can drift.
 
 
-| class        | overflow after           | Notes               |
-|:-------------|:-------------------------|:--------------------|
-| seconds      | 49 days, 17:02:47        | based upon millis() |
-| milliSeconds | 49 days, 17:02:47.297    |
-| microSeconds | 00 days  01:11:34.967296 |
+|  class         |  overflow after            |  Notes                |
+|:---------------|:---------------------------|:----------------------|
+|  seconds       |  49 days, 17:02:47         |  based upon millis()  |
+|  milliSeconds  |  49 days, 17:02:47.297     |
+|  microSeconds  |  00 days  01:11:34.967296  |
 
 
 ## Applications
@@ -59,19 +59,26 @@ See examples.
 
 ## Future
 
+#### must
 - test on ESP32
-- nanos() on ESP32 ?
-- implement printable interface (add unit)
-  - ?
-- implement toClock()
+
+#### should
+- implement toClock() 
   - idea to give it a clock print layout
   - seconds.toClock() -> DD 12:34:56
   - milliSeconds.toClock(3) -> 12:23:45.123    (3) == 3 decimals..
   - milliSeconds.toClock(1) -> 12:23:45.1
   - microSeconds.toCLock()  -> 12:23:45.123456  ???
+  - printHelpers class?
 - implement toSeconds()
   - double milliSeconds.toSeconds() -> 45.123
   - double microSeconds.toSeconds() -> 45.123456
+
+#### could
+- nanos() on ESP32 ?
+- implement printable interface
+  - add unit (s, ms, us)
+  - what layout to use?
 - update documentation
 - rounding effect, describe
 
diff --git a/library.json b/library.json
index 3622925..9c1e68f 100644
--- a/library.json
+++ b/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/timing"
   },
-  "version": "0.2.3",
+  "version": "0.2.4",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*",
diff --git a/library.properties b/library.properties
index 266424e..0d21e45 100644
--- a/library.properties
+++ b/library.properties
@@ -1,5 +1,5 @@
 name=timing
-version=0.2.3
+version=0.2.4
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library with wrapper classes for seconds millis micros. 
diff --git a/timing.h b/timing.h
index f122844..ad607ba 100644
--- a/timing.h
+++ b/timing.h
@@ -2,21 +2,12 @@
 // 
 //    FILE: timing.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.2.3
+// VERSION: 0.2.4
 // PURPOSE: Arduino library with wrapper classes for seconds millis micros 
 //     URL: https://github.com/RobTillaart/timing
-//
-//  HISTORY: 
-//  0.1.00  2011-01-04   initial version
-//  0.1.01  2011-07-19   lib version
-//  0.1.02  2015-03-02   move all to mymillis.h file so compiler can optimize
-//  0.2.0   2020-07-07   renamed to timing.h
-//  0.2.1   2021-01-09   added Arduino-CI + unit test
-//  0.2.2   2021-05-27   added Arduino-lint
-//  0.2.3   2021-12-29   update library.json, license, minor edits
 
 
-#define TIMING_LIB_VERSION        (F("0.2.3"))
+#define TIMING_LIB_VERSION        (F("0.2.4"))
 
 
 class microSeconds
@@ -49,8 +40,8 @@ class seconds
 {
 public:
   seconds()                       { set(0); }
-  uint32_t now()                  { return millis()/1000UL - _offset; }
-  void set(uint32_t value = 0UL)  { _offset = millis()/1000UL - value; }
+  uint32_t now()                  { return millis() / 1000UL - _offset; }
+  void set(uint32_t value = 0UL)  { _offset = millis() / 1000UL - value; }
   uint32_t getOffset()            { return _offset; };
 
 private: