diff --git a/libraries/Multiplex/.github/workflows/arduino_test_runner.yml b/libraries/Multiplex/.github/workflows/arduino_test_runner.yml
index 476456bb..096b975b 100644
--- a/libraries/Multiplex/.github/workflows/arduino_test_runner.yml
+++ b/libraries/Multiplex/.github/workflows/arduino_test_runner.yml
@@ -4,10 +4,14 @@ name: Arduino CI
 on: [push, pull_request]
 
 jobs:
-  arduino_ci:
+  runTest:
     runs-on: ubuntu-latest
 
     steps:
       - uses: actions/checkout@v2
-      - uses: Arduino-CI/action@master
-          #   Arduino-CI/action@v0.1.1
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 2.6
+      - run: |
+          gem install arduino_ci
+          arduino_ci.rb
diff --git a/libraries/Multiplex/Multiplex.cpp b/libraries/Multiplex/Multiplex.cpp
index 27d9b9dc..65181374 100644
--- a/libraries/Multiplex/Multiplex.cpp
+++ b/libraries/Multiplex/Multiplex.cpp
@@ -1,7 +1,7 @@
 //
 //    FILE: Multiplex.cpp
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.2.0
+// VERSION: 0.2.1
 // PURPOSE: Arduino library to multiplex streams
 //    DATE: 2021-01-09
 //     URL: https://github.com/RobTillaart/Multiplex
@@ -9,6 +9,10 @@
 //  HISTORY:
 //  0.1.0   2021-01-09  initial version
 //  0.2.0   2021-08-09  See issues #2 and #3
+//  0.2.1   2021-09-12  made index(Stream) public; added stream(index)
+//                      enable() / disable() return true on success
+//                      added free() function
+//                      minor refactor.
 
 
 #include "Multiplex.h"
@@ -16,22 +20,33 @@
 
 Multiplex::Multiplex()
 {
+  // malloc ?
+  _size = MAX_MULTIPLEX;
   reset();
 }
 
 
+Multiplex::~Multiplex()
+{
+  // free ?
+}
+
+
 void Multiplex::reset()
 {
-  _size = MAX_MULTIPLEX;
-  for (int i = 0; i < _size; i++) _enabled[i] = false;
+  for (uint8_t i = 0; i < _size; i++)
+  {
+    _enabled[i] = false;
+  }
   _count = 0;
 }
 
 
 bool Multiplex::add(Print * stream)
 {
-  if (index(stream) != 0xFF) return false;
   if (_count >= _size) return false;
+  if (index(stream) != 0xFF) return false;
+
   _enabled[_count]  = true;
   _stream[_count++] = stream;
   return true;
@@ -44,7 +59,7 @@ bool Multiplex::add(Print * stream)
 //
 size_t Multiplex::write(uint8_t c)
 {
-  uint8_t n = 0;
+  size_t n = 0;
   for (uint8_t i = 0; i < _count; i++)
   {
     if (_enabled[i])
@@ -55,8 +70,10 @@ size_t Multiplex::write(uint8_t c)
   return n;
 }
 
-size_t Multiplex::write(const uint8_t *buffer, size_t size) {
-  uint8_t n = 0;
+
+size_t Multiplex::write(const uint8_t *buffer, size_t size)
+{
+  size_t n = 0;
   for (uint8_t i = 0; i < _count; i++)
   {
     if (_enabled[i])
@@ -67,11 +84,10 @@ size_t Multiplex::write(const uint8_t *buffer, size_t size) {
   return n;
 }
 
-// private
+
 uint8_t Multiplex::index(Print *stream) 
 {
-  uint8_t i = 0;
-  for (; i < _count; i++)
+  for (uint8_t i = 0; i < _count; i++)
   {
     if (stream == _stream[i]) 
     {
@@ -81,35 +97,53 @@ uint8_t Multiplex::index(Print *stream)
   return 0xFF;
 }
 
-void Multiplex::enable(uint8_t n)
+
+Print * Multiplex::stream(uint8_t n) 
 {
-  if (n < _count && n != 0xFF) _enabled[n] = true;
+  if (n >= _count) return NULL;
+  return _stream[n];
 }
 
-void Multiplex::enableStream(Print *stream)
+
+bool Multiplex::enable(uint8_t n)
+{
+  if (n >= _count) return false;
+  _enabled[n] = true;
+  return true;
+}
+
+
+bool Multiplex::enableStream(Print *stream)
 {
   return enable(index(stream));
 }
 
-void Multiplex::disable(uint8_t n)
+
+bool Multiplex::disable(uint8_t n)
 {
-  if (n != 0xFF && n < _count) _enabled[n] = false;
+  if (n >= _count) return false;
+  _enabled[n] = false;
+  return true;
 }
 
-void Multiplex::disableStream(Print *stream)
+
+bool Multiplex::disableStream(Print *stream)
 {
   return disable(index(stream));
 }
 
+
 bool Multiplex::isEnabled(uint8_t n)
 {
-  if (n != 0xFF && n >= _count) return false;
+  if (n >= _count) return false;
   return _enabled[n];
 }
 
+
 bool Multiplex::isEnabledStream(Print *stream)
 {
   return isEnabled(index(stream));
 }
 
+
 // -- END OF FILE --
diff --git a/libraries/Multiplex/Multiplex.h b/libraries/Multiplex/Multiplex.h
index 66503e6e..ae2a3a8b 100644
--- a/libraries/Multiplex/Multiplex.h
+++ b/libraries/Multiplex/Multiplex.h
@@ -2,7 +2,7 @@
 //
 //    FILE: Multiplex.h
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.2.0
+// VERSION: 0.2.1
 // PURPOSE: Arduino library to multiplex streams 
 //    DATE: 2021-01-09
 //     URL: https://github.com/RobTillaart/Multiplex
@@ -12,39 +12,52 @@
 //#include "Print.h"
 
 
-#define MULTIPLEX_LIB_VERSION      (F("0.2.0"))
+#define MULTIPLEX_LIB_VERSION      (F("0.2.1"))
 
 
-const uint8_t MAX_MULTIPLEX = 4;
+#ifndef MAX_MULTIPLEX
+#define MAX_MULTIPLEX       4             // MAX 254 as 0xFF is a special value.
+#endif
 
 
 class Multiplex: public Print
 {
 public:
   Multiplex();
-  
+  ~Multiplex();
+
+
   // CORE
-  virtual size_t  write(uint8_t c) override;
+  virtual size_t write(uint8_t c) override;
   virtual size_t write(const uint8_t *buffer, size_t size) override;
   bool    add(Print * stream);  // returns true on success
   void    reset();
 
+
   // CONTROL
-  uint8_t count()       { return _count; };
-  uint8_t size()        { return _size; };
-  void    enable(uint8_t index);
-  void    enableStream(Print * stream);
-  void    disable(uint8_t index);
-  void    disableStream(Print * stream);
+  uint8_t count() { return _count; };
+  uint8_t size()  { return _size; };
+  uint8_t free()  { return _size - _count; };
+
+  // returns true on success, false otherwise.
+  bool    enable(uint8_t index);
+  bool    enableStream(Print * stream);
+  bool    disable(uint8_t index);
+  bool    disableStream(Print * stream);
+
   bool    isEnabled(uint8_t index);
   bool    isEnabledStream(Print * stream);
 
+  uint8_t index(Print *stream);
+  Print * stream(uint8_t index);
+
+
 private:
   Print * _stream[MAX_MULTIPLEX];
-  bool    _enabled[MAX_MULTIPLEX];  // bitmask max 4 ...
+  bool    _enabled[MAX_MULTIPLEX];
+
   uint8_t _count;
   uint8_t _size;
-  uint8_t index(Print *stream);
 };
 
 // -- END OF FILE --
diff --git a/libraries/Multiplex/README.md b/libraries/Multiplex/README.md
index cf3b1ee6..143ddc63 100644
--- a/libraries/Multiplex/README.md
+++ b/libraries/Multiplex/README.md
@@ -1,60 +1,85 @@
 
 [![Arduino CI](https://github.com/RobTillaart/Multiplex/workflows/Arduino%20CI/badge.svg)](https://github.com/marketplace/actions/arduino_ci)
+[![JSON check](https://github.com/RobTillaart/Multiplex/actions/workflows/jsoncheck.yml/badge.svg)](https://github.com/RobTillaart/Multiplex/actions/workflows/jsoncheck.yml)
+[![Arduino-lint](https://github.com/RobTillaart/Multiplex/actions/workflows/arduino-lint.yml/badge.svg)](https://github.com/RobTillaart/Multiplex/actions/workflows/arduino-lint.yml)
 [![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/Multiplex/blob/master/LICENSE)
 [![GitHub release](https://img.shields.io/github/release/RobTillaart/Multiplex.svg?maxAge=3600)](https://github.com/RobTillaart/Multiplex/releases)
 
 # Multiplex
 
-Arduino Library implementing a stream multiplexer.
+Arduino Library implementing a (Print) stream multiplexer.
+
 
 ## Description
 
-Multiplex is a library in which one can add multiple Print streams. 
+Multiplex is a library in which one can add multiple Print streams.
+If one prints to the multiplexer the data is sent to all the streams that were added.
 
-If one prints to the multiplexer it is sent to all the streams that were added.
-
-The maximum nr of streams to add is 4.
-
-It is possible to disable individual streams.
+The maximum number of streams to add is 4. This value is defined in the **multiplex.h file** with `#define MAX_MULTIPLEX`
+This value can be set to 254 MAX as the number 255 / 0xFF is used as a NOT_FOUND flag.
 
 Streams can be enabled or disabled by calling `enable()/disable()` passing either an index (based on the order 
-in whicbh `add` was called; 0 is first) or a pointer to the `Print` 
-object that was passed to `add(Print *)`;
+in which `add` was called; 0 is first) or a pointer to the `Print` 
+object that was passed to `add(Print *)` by calling `enableStream()/disableStream()`
+
+It is not possible to remove a stream from the multiplexer (yet), as this would affect the indices used.
+Solution is to reset and repopulate for now.
+
 
 ## Interface
 
+
 ### Constructor
 
-- **Multiplex()** constructor
-- **void reset()** resets to zero streams in the multiplexer.
+- **Multiplex(uint8_t max_multiplex = 4)** constructor, 
+sets the maximum number of streams to 4 by default. 
+MAX number is 254 as 255 (0xFF) is used as a flag for **NOT FOUND**.
+- **~Multiplex()** destructor
+- **void reset()** resets the count in the multiplexer to zero streams.
+
 
 ### Core
 
-- **size_t write(uint8_t c)** workhorse of the print interface.
+- **size_t write(uint8_t c)** workhorse of the print interface. 
+Writes a character to all enabled streams.
+- **size_t write(const uint8_t \*buffer, size_t size)** 
+Writes a buffer of size characters to all enabled streams.
 - **bool add(Print \* stream)** add another print stream. 
 Returns false if no space left.
 
 
 ### Control
 
-- **uint8_t count()** returns # streams, MAX 4 in initial release
+- **uint8_t count()** returns number of streams added, MAX 4 in initial release
 - **uint8_t size()** returns size which is 4 in the current release.
-- **void enable(uint8_t index)** enable the stream at index.
-- **void enableStream(Stream * stream)** enable the stream.
-- **void disable(uint8_t index)** disable the stream at index.
-- **void disableStream(Stream * stream)** disable the stream.
-- **bool isEnabled(uint8_t index)** checks if the stream at index is enabled.
-- **bool isEnabledStream(Stream * stream)** checks if the stream is enabled.
+- **uint8_t free()** returns number of free slots.
+- **bool enable(uint8_t index)** enable the stream at index.
+Returns true on success, false otherwise.
+- **bool enableStream(Stream \* stream)** enable the stream.
+Returns true on success, false otherwise.
+- **bool disable(uint8_t index)** disable the stream at index.
+Returns true on success, false otherwise.
+- **bool disableStream(Stream \* stream)** disable the stream.
+Returns true on success, false otherwise.
+- **bool isEnabled(uint8_t index)** returns true if the stream at index is enabled,
+false otherwise.
+- **bool isEnabledStream(Stream \* stream)** returns true if the stream is enabled,
+false otherwise.
+- **uint8_t index(Print \*stream)** returns the index of the stream if it was added,
+otherwise it returns 0xFF == 255.  
+Can be used to check if a stream is added the multiplexer.
+- **Print \* stream(uint8_t index)** returns the stream at index or NULL otherwise.
+Convenience function.
 
 
 ## Future
 
-- set size in constructor
+- set size in constructor - dynamic memory
+- pack enabled flag in one or more bytes
 - add names?
-- bool inMp(stream)
-- add returns int index?  or 0xFF for fail
-- remove a stream from the multiplex ???  => complexer admin.
-- increase up to 8 streams. (pack enabled flag in one byte)
+- remove a stream from the multiplex ?  
+`bool remove(Print * stream); plus  bool remove(uint8_t idx) ?`
+- iterate over the streams?   `Print * getStream(idx)`
 
 
 ## Operation
diff --git a/libraries/Multiplex/examples/Multiplex_enable_stream/Multiplex_enable_stream.ino b/libraries/Multiplex/examples/Multiplex_enable_stream/Multiplex_enable_stream.ino
new file mode 100644
index 00000000..a0dc0be1
--- /dev/null
+++ b/libraries/Multiplex/examples/Multiplex_enable_stream/Multiplex_enable_stream.ino
@@ -0,0 +1,65 @@
+//
+//    FILE: Multiplex_enable_stream.ino
+//  AUTHOR: Rob Tillaart
+// VERSION: 0.2.1
+// PURPOSE: demo
+//    DATE: 2021-089-10
+
+
+#include "Multiplex.h"
+
+
+Multiplex mp;
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+
+  mp.add(&Serial);
+  mp.println("one");
+  mp.add(&Serial);
+  mp.println("one++");
+
+  for (int i = 0; i < mp.count(); i++)
+  {
+    Serial.print("isEnabled ");
+    Serial.print(i);
+    Serial.print(":\t");
+    Serial.println(mp.isEnabled(i));
+  }
+
+  mp.disableStream(&Serial);
+  mp.println("two");
+
+  for (int i = 0; i < mp.count(); i++)
+  {
+    Serial.print("isEnabled ");
+    Serial.print(i);
+    Serial.print(":\t");
+    Serial.println(mp.isEnabled(i));
+  }
+
+  mp.disableStream(&Serial);
+  mp.println("three");
+
+  for (int i = 0; i < mp.count(); i++)
+  {
+    Serial.print("isEnabled ");
+    Serial.print(i);
+    Serial.print(":\t");
+    Serial.println(mp.isEnabled(i));
+  }
+
+  mp.enableStream(&Serial);
+  mp.println("\n Done...\n");
+}
+
+
+void loop()
+{
+}
+
+
+// -- END OF FILE --
diff --git a/libraries/Multiplex/examples/Multiplex_softwareSerial/Multiplex_softwareSerial.ino b/libraries/Multiplex/examples/Multiplex_softwareSerial/Multiplex_softwareSerial.ino
index 747d32ea..c521ffd7 100644
--- a/libraries/Multiplex/examples/Multiplex_softwareSerial/Multiplex_softwareSerial.ino
+++ b/libraries/Multiplex/examples/Multiplex_softwareSerial/Multiplex_softwareSerial.ino
@@ -1,21 +1,25 @@
 //
 //    FILE: Multiplex_softwareSerial.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.1.0
+// VERSION: 0.2.1
 // PURPOSE: demo
 //    DATE: 2021-01-17
 
+
 #include "Multiplex.h"
 #include <SoftwareSerial.h>
 
+
 // one multiplexer
 Multiplex mp;
 
+
 // three serial outputs
 SoftwareSerial Serial_A(-1, 8);
 SoftwareSerial Serial_B(-1, 9);
 SoftwareSerial Serial_C(-1, 10);
 
+
 void setup()
 {
   Serial.begin(115200);
@@ -41,7 +45,7 @@ void setup()
   Serial.print("count: ");
   Serial.println(n);
 
-  mp.disable(&Serial_B);
+  mp.disableStream(&Serial_B);
 
   for (int i = 0; i < mp.count(); i++)
   {
@@ -52,11 +56,10 @@ void setup()
   }
   
   mp.println("\nThis should only print on Serial_A and Serial_C\n");
-
   mp.println("Done...\n");
-
 }
 
+
 void loop()
 {
 }
diff --git a/libraries/Multiplex/examples/Multiplex_test/Multiplex_test.ino b/libraries/Multiplex/examples/Multiplex_test/Multiplex_test.ino
index 62408670..ab0f0ea8 100644
--- a/libraries/Multiplex/examples/Multiplex_test/Multiplex_test.ino
+++ b/libraries/Multiplex/examples/Multiplex_test/Multiplex_test.ino
@@ -1,14 +1,17 @@
 //
 //    FILE: Multiplex_test.ino
 //  AUTHOR: Rob Tillaart
-// VERSION: 0.2.0
+// VERSION: 0.2.1
 // PURPOSE: demo
 //    DATE: 2021-01-09
 
+
 #include "Multiplex.h"
 
+
 Multiplex mp;
 
+
 class FakeStream : public Print
 {
   public:
@@ -36,6 +39,7 @@ class FakeStream : public Print
   uint8_t _id = 0;
 };
 
+
 void setup()
 {
   Serial.begin(115200);
@@ -96,9 +100,9 @@ void setup()
   }
 
   mp.print("Done...\n");
-
 }
 
+
 void loop()
 {
 }
diff --git a/libraries/Multiplex/keywords.txt b/libraries/Multiplex/keywords.txt
index de78b0d1..9ac5d031 100644
--- a/libraries/Multiplex/keywords.txt
+++ b/libraries/Multiplex/keywords.txt
@@ -1,14 +1,19 @@
-# Syntax Coloring Map for Multiplex
+# Syntax Colouring Map for Multiplex
 
-# Datatypes (KEYWORD1)
+
+# Data types (KEYWORD1)
 Multiplex	KEYWORD1
 
+
 # Methods and Functions (KEYWORD2)
 write	KEYWORD2
 add	KEYWORD2
 reset	KEYWORD2
+
 count	KEYWORD2
 size	KEYWORD2
+free	KEYWORD2
+
 enable	KEYWORD2
 disable	KEYWORD2
 isEnabled	KEYWORD2
@@ -16,7 +21,7 @@ isEnabled	KEYWORD2
 enableStream	KEYWORD2
 disableStream	KEYWORD2
 isEnabledStream	KEYWORD2
-
+index	KEYWORD2
 
 # Constants (LITERAL1)
 MULTIPLEX_LIB_VERSION	LITERAL1
diff --git a/libraries/Multiplex/library.json b/libraries/Multiplex/library.json
index c06d29db..edf2c29a 100644
--- a/libraries/Multiplex/library.json
+++ b/libraries/Multiplex/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/Multiplex"
   },
-  "version": "0.2.0",
+  "version": "0.2.1",
   "license": "MIT",
   "frameworks": "arduino",
   "platforms": "*"
diff --git a/libraries/Multiplex/library.properties b/libraries/Multiplex/library.properties
index 995be85e..a70457cf 100644
--- a/libraries/Multiplex/library.properties
+++ b/libraries/Multiplex/library.properties
@@ -1,5 +1,5 @@
 name=Multiplex
-version=0.2.0
+version=0.2.1
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino Library implementing a stream multiplexer