From f764634eeb1161525c49adfcdaea83cb8d9e5c4a Mon Sep 17 00:00:00 2001
From: Rob Tillaart <rob.tillaart@gmail.com>
Date: Mon, 11 Dec 2023 09:17:06 +0100
Subject: [PATCH] 0.4.0 PCF8574

---
 libraries/PCF8574/CHANGELOG.md                | 10 ++-
 libraries/PCF8574/PCF8574.cpp                 | 19 +----
 libraries/PCF8574/PCF8574.h                   |  7 +-
 libraries/PCF8574/README.md                   | 30 +++++---
 .../examples/PCF8574_Wire2/PCF8574_Wire2.ino  |  8 +-
 .../PCF8574_interrupt/PCF8574_interrupt.ino   | 11 +--
 .../PCF8574_isConnected.ino                   |  8 +-
 .../PCF8574_performance.ino                   |  6 +-
 .../PCF8574_rotaryEncoder.ino                 |  7 +-
 .../PCF8574_select/PCF8574_select.ino         | 13 ++--
 .../examples/PCF8574_test/PCF8574_test.ino    |  6 +-
 .../examples/PCF8574_test1/PCF8574_test1.ino  | 14 ++--
 .../examples/PCF8574_test2/PCF8574_test2.ino  | 14 ++--
 .../PCF8574_test_ESP32/.arduino-ci.yml        | 27 +++++++
 .../PCF8574_test_ESP32/PCF8574_test_ESP32.ino | 73 ++++++++++++++++++
 .../PCF8574_test_RP2040/.arduino-ci.yml       | 27 +++++++
 .../PCF8574_test_RP2040.ino                   | 75 +++++++++++++++++++
 .../examples/buttonRead/buttonRead.ino        | 32 ++++----
 .../examples/buttonRead8/buttonRead8.ino      | 20 +++--
 libraries/PCF8574/library.json                |  2 +-
 libraries/PCF8574/library.properties          |  2 +-
 libraries/PCF8574/test/unit_test_001.cpp      |  6 +-
 22 files changed, 323 insertions(+), 94 deletions(-)
 create mode 100644 libraries/PCF8574/examples/PCF8574_test_ESP32/.arduino-ci.yml
 create mode 100644 libraries/PCF8574/examples/PCF8574_test_ESP32/PCF8574_test_ESP32.ino
 create mode 100644 libraries/PCF8574/examples/PCF8574_test_RP2040/.arduino-ci.yml
 create mode 100644 libraries/PCF8574/examples/PCF8574_test_RP2040/PCF8574_test_RP2040.ino

diff --git a/libraries/PCF8574/CHANGELOG.md b/libraries/PCF8574/CHANGELOG.md
index 53443ce1..d27e63d7 100644
--- a/libraries/PCF8574/CHANGELOG.md
+++ b/libraries/PCF8574/CHANGELOG.md
@@ -6,12 +6,20 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 
+## [0.4.0] - 2023-09-23
+- refactor API, begin()
+- update readme.md
+- update examples
+- add examples ESP32 RP2040
+- minor edits
+
+----
+
 ## [0.3.9] - 2023-09-23
 - Add Wire1 support for ESP32
 - update readme.md
 - minor edits
 
-
 ## [0.3.8] - 2023-02-04
 - update readme.md
 - update GitHub actions
diff --git a/libraries/PCF8574/PCF8574.cpp b/libraries/PCF8574/PCF8574.cpp
index eb6f176e..ac7e8b0a 100644
--- a/libraries/PCF8574/PCF8574.cpp
+++ b/libraries/PCF8574/PCF8574.cpp
@@ -2,7 +2,7 @@
 //    FILE: PCF8574.cpp
 //  AUTHOR: Rob Tillaart
 //    DATE: 02-febr-2013
-// VERSION: 0.3.9
+// VERSION: 0.4.0
 // PURPOSE: Arduino library for PCF8574 - 8 channel I2C IO expander
 //     URL: https://github.com/RobTillaart/PCF8574
 //          http://forum.arduino.cc/index.php?topic=184800
@@ -22,25 +22,8 @@ PCF8574::PCF8574(const uint8_t deviceAddress, TwoWire *wire)
 }
 
 
-#if defined (ESP8266) || defined(ESP32)
-bool PCF8574::begin(int dataPin, int clockPin, uint8_t value)
-{
-  if ((dataPin < 255) && (clockPin < 255))
-  {
-    _wire->begin(dataPin, clockPin);
-  } else {
-    _wire->begin();
-  }
-  if (! isConnected()) return false;
-  PCF8574::write8(value);
-  return true;
-}
-#endif
-
-
 bool PCF8574::begin(uint8_t value)
 {
-  _wire->begin();
   if (! isConnected()) return false;
   PCF8574::write8(value);
   return true;
diff --git a/libraries/PCF8574/PCF8574.h b/libraries/PCF8574/PCF8574.h
index 331922d6..494383f5 100644
--- a/libraries/PCF8574/PCF8574.h
+++ b/libraries/PCF8574/PCF8574.h
@@ -3,7 +3,7 @@
 //    FILE: PCF8574.h
 //  AUTHOR: Rob Tillaart
 //    DATE: 02-febr-2013
-// VERSION: 0.3.9
+// VERSION: 0.4.0
 // PURPOSE: Arduino library for PCF8574 - 8 channel I2C IO expander
 //     URL: https://github.com/RobTillaart/PCF8574
 //          http://forum.arduino.cc/index.php?topic=184800
@@ -13,7 +13,7 @@
 #include "Wire.h"
 
 
-#define PCF8574_LIB_VERSION         (F("0.3.9"))
+#define PCF8574_LIB_VERSION         (F("0.4.0"))
 
 #ifndef PCF8574_INITIAL_VALUE
 #define PCF8574_INITIAL_VALUE       0xFF
@@ -29,9 +29,6 @@ class PCF8574
 public:
   explicit PCF8574(const uint8_t deviceAddress = 0x20, TwoWire *wire = &Wire);
 
-#if defined (ESP8266) || defined(ESP32)
-  bool    begin(int sda, int scl, uint8_t value = PCF8574_INITIAL_VALUE);
-#endif
   bool    begin(uint8_t value = PCF8574_INITIAL_VALUE);
   bool    isConnected();
 
diff --git a/libraries/PCF8574/README.md b/libraries/PCF8574/README.md
index bf82b9af..86092132 100644
--- a/libraries/PCF8574/README.md
+++ b/libraries/PCF8574/README.md
@@ -49,6 +49,15 @@ There are two examples to show how interrupts can be used:
 - PCF8574_rotaryEncoder.ino
 
 
+#### 0.4.0 Breaking change
+
+Version 0.4.0 introduced a breaking change.
+You cannot set the pins in **begin()** any more.
+This reduces the dependency of processor dependent Wire implementations.
+The user has to call **Wire.begin()** and can optionally set the Wire pins 
+before calling **begin()**.
+
+
 #### Related
 
 16 bit port expanders
@@ -87,24 +96,23 @@ However when performance is needed you can try to overclock the chip.
 #include "PCF8574.h"
 ```
 
-**PCF8574_INITIAL_VALUE** is a define that can be set compile time or before
+**PCF8574_INITIAL_VALUE** is a define 0xFF that can be set compile time or before
 the include of "pcf8574.h" to overrule the default value used with the **begin()** call.
 
 
-### Constructor
+#### Constructor
 
-- **PCF8574(uint8_t deviceAddress = 0x20, TwoWire \*wire = &Wire)** Constructor with optional device address, default 0x20, 
+- **PCF8574(uint8_t deviceAddress = 0x20, TwoWire \*wire = &Wire)** Constructor with optional address, default 0x20, 
 and the optional Wire interface as parameter.
-- **bool begin(uint8_t value = PCF8574_INITIAL_VALUE)** set the initial value for the pins and masks.
-- **bool begin(int sda, int scl, uint8_t value = PCF8574_INITIAL_VALUE)** idem, for the ESP32 where one can choose the I2C pins.
+- **bool begin(uint8_t value = PCF8574_INITIAL_VALUE)** set the initial value (default 0xFF) for the pins and masks.
 - **bool isConnected()** checks if the address set in the constructor or by **setAddress()** is visible on the I2C bus.
 - **bool setAddress(const uint8_t deviceAddress)** sets the device address after construction. 
 Can be used to switch between PCF8574 modules runtime. Note this corrupts internal buffered values, 
 so one might need to call **read8()** and/or **write8()**. Returns true if address can be found on I2C bus.
-- **uint8_t getAddress()** returns the device address.
+- **uint8_t getAddress()** Returns the device address.
 
 
-### Read and Write
+#### Read and Write
 
 - **uint8_t read8()** reads all 8 pins at once. This one does the actual reading.
 - **uint8_t read(uint8_t pin)** reads a single pin; pin = 0..7
@@ -116,7 +124,7 @@ value is HIGH(1) or LOW (0)
 - **uint8_t valueOut()** returns the last written data.
 
 
-### Button
+#### Button
 
 The **"button"** functions are to be used when you mix input and output on one IC.
 It does not change / affect the pins used for output by masking these.
@@ -133,7 +141,7 @@ Note this can be a subset of the pins set with **setButtonMask()** if one wants
 Background - https://github.com/RobTillaart/Arduino/issues/38
 
 
-### Special
+#### Special
 
 - **void toggle(const uint8_t pin)** toggles a single pin
 - **void toggleMask(const uint8_t mask = 0xFF)** toggles a selection of pins, 
@@ -147,7 +155,7 @@ Fills the lower lines with zero's.
 - **void reverse()** reverse the "bit pattern" of the lines, swapping pin 7 with 0, 6 with 1, 5 with 2 etc.
 
 
-### Select
+#### Select
 
 Some convenience wrappers.
 
@@ -161,7 +169,7 @@ This can typical be used to implement a VU meter.
 - **void selectAll()** sets all pins to HIGH.
 
 
-### Miscellaneous
+#### Miscellaneous
 
 - **int lastError()** returns the last error from the lib. (see .h file).
 
diff --git a/libraries/PCF8574/examples/PCF8574_Wire2/PCF8574_Wire2.ino b/libraries/PCF8574/examples/PCF8574_Wire2/PCF8574_Wire2.ino
index 73863e5b..30132690 100644
--- a/libraries/PCF8574/examples/PCF8574_Wire2/PCF8574_Wire2.ino
+++ b/libraries/PCF8574/examples/PCF8574_Wire2/PCF8574_Wire2.ino
@@ -2,12 +2,12 @@
 //    FILE: PCF8574_Wire2.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2016-04-30
-// PUPROSE: demo
+// PURPOSE: demo
 
 
 #include "PCF8574.h"
 
-// adjust addresses if needed
+//  adjust addresses if needed
 PCF8574 PCF(0x39, &Wire2);
 
 
@@ -18,6 +18,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire2.begin();
+
   if (!PCF.begin())
   {
     Serial.println("could not initialize...");
@@ -75,5 +77,5 @@ void doToggle()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_interrupt/PCF8574_interrupt.ino b/libraries/PCF8574/examples/PCF8574_interrupt/PCF8574_interrupt.ino
index b215162a..abe11e70 100644
--- a/libraries/PCF8574/examples/PCF8574_interrupt/PCF8574_interrupt.ino
+++ b/libraries/PCF8574/examples/PCF8574_interrupt/PCF8574_interrupt.ino
@@ -2,7 +2,7 @@
 //    FILE: PCF8574_interrupt.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2020-12-07
-// PUPROSE: test PCF8574 library
+// PURPOSE: test PCF8574 library
 //
 // TEST SETUP
 //   Connect INT pin of the PCF8574 to UNO pin 2
@@ -19,7 +19,7 @@ PCF8574 PCF(0x38);
 
 ////////////////////////////////////
 //
-// INTERRUPT ROUTINE + FLAG
+//  INTERRUPT ROUTINE + FLAG
 //
 const int IRQPIN = 2;
 
@@ -33,7 +33,7 @@ void pcf_irq()
 
 ////////////////////////////////////
 //
-// MAIN CODE
+//  MAIN CODE
 //
 void setup()
 {
@@ -41,7 +41,8 @@ void setup()
   Serial.println(__FILE__);
   Serial.print("PCF8574_LIB_VERSION: ");
   Serial.println(PCF8574_LIB_VERSION);
-
+  
+  Wire.begin();
   PCF.begin();
 
   pinMode(IRQPIN, INPUT_PULLUP);
@@ -67,5 +68,5 @@ void loop()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_isConnected/PCF8574_isConnected.ino b/libraries/PCF8574/examples/PCF8574_isConnected/PCF8574_isConnected.ino
index 8bdf5d21..22a45661 100644
--- a/libraries/PCF8574/examples/PCF8574_isConnected/PCF8574_isConnected.ino
+++ b/libraries/PCF8574/examples/PCF8574_isConnected/PCF8574_isConnected.ino
@@ -2,12 +2,12 @@
 //    FILE: PCF8574_isConnected.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2021-01-03
-// PUPROSE: demo isConnected function
+// PURPOSE: demo isConnected function
 
 
 #include "PCF8574.h"
 
-// adjust addresses if needed
+//  adjust addresses if needed
 PCF8574 PCF_39(0x39);
 
 
@@ -18,6 +18,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire.begin();
+
   if (!PCF_39.begin())
   {
     Serial.println("could not initialize...");
@@ -38,5 +40,5 @@ void loop()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_performance/PCF8574_performance.ino b/libraries/PCF8574/examples/PCF8574_performance/PCF8574_performance.ino
index 12c43210..93fe865f 100644
--- a/libraries/PCF8574/examples/PCF8574_performance/PCF8574_performance.ino
+++ b/libraries/PCF8574/examples/PCF8574_performance/PCF8574_performance.ino
@@ -2,7 +2,7 @@
 //    FILE: PCF8574_performance.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2021-01-24
-// PUPROSE: test PCF8574 library at different I2C speeds.
+// PURPOSE: test PCF8574 library at different I2C speeds.
 
 
 #include "PCF8574.h"
@@ -19,6 +19,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire.begin();
+
   PCF.begin();
   Serial.println(PCF.isConnected());
 
@@ -50,4 +52,4 @@ void loop()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
diff --git a/libraries/PCF8574/examples/PCF8574_rotaryEncoder/PCF8574_rotaryEncoder.ino b/libraries/PCF8574/examples/PCF8574_rotaryEncoder/PCF8574_rotaryEncoder.ino
index cc1d9357..2051b3ed 100644
--- a/libraries/PCF8574/examples/PCF8574_rotaryEncoder/PCF8574_rotaryEncoder.ino
+++ b/libraries/PCF8574/examples/PCF8574_rotaryEncoder/PCF8574_rotaryEncoder.ino
@@ -2,7 +2,7 @@
 //    FILE: PCF8574_rotaryEncoder.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2021-05-08
-// PUPROSE: demo PCF8574 as rotary encoder reader.
+// PURPOSE: demo PCF8574 as rotary encoder reader.
 //
 //
 //  RotaryEncoder    PCF8574      UNO
@@ -49,6 +49,7 @@ void setup()
   flag = false;
 
   Wire.begin();
+
   if (decoder.begin() == false)
   {
     Serial.println("\nERROR: cannot communicate to PCF8574.");
@@ -101,7 +102,7 @@ void updateRotaryDecoder()
 {
   uint8_t val = decoder.read8();
 
-  // check which of 4 has changed
+  //  check which of 4 has changed
   for (uint8_t i = 0; i < 4; i++)
   {
     uint8_t currentpos = (val & 0x03);
@@ -130,5 +131,5 @@ void updateRotaryDecoder()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_select/PCF8574_select.ino b/libraries/PCF8574/examples/PCF8574_select/PCF8574_select.ino
index 952d4fe7..d06d8a28 100644
--- a/libraries/PCF8574/examples/PCF8574_select/PCF8574_select.ino
+++ b/libraries/PCF8574/examples/PCF8574_select/PCF8574_select.ino
@@ -2,8 +2,7 @@
 //    FILE: PCF8574_select.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2022-06-18
-// PUPROSE: demo PCF8574 library select functions
-
+// PURPOSE: demo PCF8574 library select functions
 
 
 #include "PCF8574.h"
@@ -20,6 +19,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire.begin();
+
   PCF.begin();
   Serial.println(PCF.isConnected());
   Serial.println();
@@ -29,14 +30,14 @@ void setup()
   PCF.selectNone();
   delay(1000);
   
-  // VU meter up
+  //  VU meter up
   for (int i = 0; i < 7; i++)
   {
     PCF.selectN(i);
     delay(100);
   }
 
-  // VU meter down
+  //  VU meter down
   for (int i = 7; i >= 0; i--)
   {
     PCF.selectN(i);
@@ -47,7 +48,7 @@ void setup()
 
 void loop()
 {
-  // night rider
+  //  night rider
   for (int i = 0; i < 7; i++)
   {
     PCF.select(i);
@@ -61,4 +62,4 @@ void loop()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
diff --git a/libraries/PCF8574/examples/PCF8574_test/PCF8574_test.ino b/libraries/PCF8574/examples/PCF8574_test/PCF8574_test.ino
index 742dab90..3a7faf2f 100644
--- a/libraries/PCF8574/examples/PCF8574_test/PCF8574_test.ino
+++ b/libraries/PCF8574/examples/PCF8574_test/PCF8574_test.ino
@@ -2,7 +2,7 @@
 //    FILE: PCF8574_test.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 7-febr-2013
-// PUPROSE: test PCF8574 library
+// PURPOSE: test PCF8574 library
 
 
 #include "PCF8574.h"
@@ -17,6 +17,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire.begin();
+
   PCF_01.begin();
 
   int x = PCF_01.read8();
@@ -66,5 +68,5 @@ void doToggle()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_test1/PCF8574_test1.ino b/libraries/PCF8574/examples/PCF8574_test1/PCF8574_test1.ino
index 09a9f493..b66a5481 100644
--- a/libraries/PCF8574/examples/PCF8574_test1/PCF8574_test1.ino
+++ b/libraries/PCF8574/examples/PCF8574_test1/PCF8574_test1.ino
@@ -2,14 +2,14 @@
 //    FILE: PCF8574_test.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 27-08-2013
-// PUPROSE: demo
+// PURPOSE: demo
 
 
 #include "PCF8574.h"
 
-// adjust addresses if needed
-PCF8574 PCF_38(0x38);  // add switches to lines  (used as input)
-PCF8574 PCF_39(0x39);  // add LEDs to lines      (used as output)
+//  adjust addresses if needed
+PCF8574 PCF_38(0x38);  //  add switches to lines  (used as input)
+PCF8574 PCF_39(0x39);  //  add LEDs to lines      (used as output)
 
 
 void setup()
@@ -19,6 +19,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire.begin();
+
   PCF_38.begin();
   PCF_39.begin();
 
@@ -65,12 +67,12 @@ void setup()
 
 void loop()
 {
-  // echo the state of the lines on the other PCF
+  //  echo the state of the lines on the other PCF
   uint8_t value = PCF_38.read8();
   PCF_39.write8(value);
   delay(100);
 }
 
 
-// END OF FILE
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_test2/PCF8574_test2.ino b/libraries/PCF8574/examples/PCF8574_test2/PCF8574_test2.ino
index 2013b74a..fee99dc5 100644
--- a/libraries/PCF8574/examples/PCF8574_test2/PCF8574_test2.ino
+++ b/libraries/PCF8574/examples/PCF8574_test2/PCF8574_test2.ino
@@ -2,13 +2,13 @@
 //    FILE: pcf8574_test2.ino
 //  AUTHOR: Rob Tillaart
 //    DATE: 2016-04-30
-// PUPROSE: demo rotateLeft, -Right and toggleMask
+// PURPOSE: demo rotateLeft, rotateRight and toggleMask
 
 
 #include "PCF8574.h"
 
-// adjust addresses if needed
-PCF8574 PCF_39(0x39);  // add LEDs to lines      (used as output)
+//  adjust addresses if needed
+PCF8574 PCF_39(0x39);  //  add LEDs to lines      (used as output)
 
 
 void setup()
@@ -18,6 +18,8 @@ void setup()
   Serial.print("PCF8574_LIB_VERSION:\t");
   Serial.println(PCF8574_LIB_VERSION);
 
+  Wire.begin();
+
   PCF_39.begin();
 
   PCF_39.write(0, 1);
@@ -51,8 +53,8 @@ void setup()
     delay(100);
   }
 
-  // 0010 0111  -> 0x27
-  // 1110 0100
+  //  0010 0111  -> 0x27
+  //  1110 0100
   PCF_39.write8(0x27);
   for (int i = 0; i < 255; i++)
   {
@@ -67,5 +69,5 @@ void loop()
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/PCF8574_test_ESP32/.arduino-ci.yml b/libraries/PCF8574/examples/PCF8574_test_ESP32/.arduino-ci.yml
new file mode 100644
index 00000000..8f24185d
--- /dev/null
+++ b/libraries/PCF8574/examples/PCF8574_test_ESP32/.arduino-ci.yml
@@ -0,0 +1,27 @@
+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
+    # - m4
+    - esp32
+    - esp8266
+    # - mega2560
+    # - rpipico
diff --git a/libraries/PCF8574/examples/PCF8574_test_ESP32/PCF8574_test_ESP32.ino b/libraries/PCF8574/examples/PCF8574_test_ESP32/PCF8574_test_ESP32.ino
new file mode 100644
index 00000000..acf7d625
--- /dev/null
+++ b/libraries/PCF8574/examples/PCF8574_test_ESP32/PCF8574_test_ESP32.ino
@@ -0,0 +1,73 @@
+//
+//    FILE: PCF8574_test_ESP32.ino
+//  AUTHOR: Rob Tillaart
+//    DATE: 7-febr-2013
+// PURPOSE: test PCF8574 library
+
+
+#include "PCF8574.h"
+
+PCF8574 PCF_01(0x38);
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("PCF8574_LIB_VERSION:\t");
+  Serial.println(PCF8574_LIB_VERSION);
+
+  //  adjust pins if needed
+  Wire.begin(20, 21);
+
+  PCF_01.begin();
+
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+  delay(1000);
+}
+
+
+void loop()
+{
+  Serial.println("HLT");
+  while (Serial.available() == 0);
+  switch (Serial.read())
+  {
+    case 'H': doHigh(); break;
+    case 'L': doLow(); break;
+    case 'T': doToggle(); break;
+  }
+}
+
+
+void doHigh()
+{
+  PCF_01.write(4, HIGH);
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+}
+
+
+void doLow()
+{
+  PCF_01.write(4, LOW);
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+}
+
+
+void doToggle()
+{
+  PCF_01.toggle(4);
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+}
+
+
+//  -- END OF FILE --
+
diff --git a/libraries/PCF8574/examples/PCF8574_test_RP2040/.arduino-ci.yml b/libraries/PCF8574/examples/PCF8574_test_RP2040/.arduino-ci.yml
new file mode 100644
index 00000000..87acfe0b
--- /dev/null
+++ b/libraries/PCF8574/examples/PCF8574_test_RP2040/.arduino-ci.yml
@@ -0,0 +1,27 @@
+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
+    # - m4
+    # - esp32
+    # - esp8266
+    # - mega2560
+    - rpipico
diff --git a/libraries/PCF8574/examples/PCF8574_test_RP2040/PCF8574_test_RP2040.ino b/libraries/PCF8574/examples/PCF8574_test_RP2040/PCF8574_test_RP2040.ino
new file mode 100644
index 00000000..d9e2d9e3
--- /dev/null
+++ b/libraries/PCF8574/examples/PCF8574_test_RP2040/PCF8574_test_RP2040.ino
@@ -0,0 +1,75 @@
+//
+//    FILE: PCF8574_test_RP2040.ino
+//  AUTHOR: Rob Tillaart
+//    DATE: 2023-12-10
+// PURPOSE: test PCF8574 library
+
+
+#include "PCF8574.h"
+
+PCF8574 PCF_01(0x38);
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("PCF8574_LIB_VERSION:\t");
+  Serial.println(PCF8574_LIB_VERSION);
+
+  //  adjust pins if needed
+  Wire.setSDA(22);
+  Wire.setSCL(23);
+  Wire.begin();
+
+  PCF_01.begin();
+
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+  delay(1000);
+}
+
+
+void loop()
+{
+  Serial.println("HLT");
+  while (Serial.available() == 0);
+  switch (Serial.read())
+  {
+    case 'H': doHigh(); break;
+    case 'L': doLow(); break;
+    case 'T': doToggle(); break;
+  }
+}
+
+
+void doHigh()
+{
+  PCF_01.write(4, HIGH);
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+}
+
+
+void doLow()
+{
+  PCF_01.write(4, LOW);
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+}
+
+
+void doToggle()
+{
+  PCF_01.toggle(4);
+  int x = PCF_01.read8();
+  Serial.print("Read ");
+  Serial.println(x, HEX);
+}
+
+
+//  -- END OF FILE --
+
diff --git a/libraries/PCF8574/examples/buttonRead/buttonRead.ino b/libraries/PCF8574/examples/buttonRead/buttonRead.ino
index 62c58117..1eddc130 100644
--- a/libraries/PCF8574/examples/buttonRead/buttonRead.ino
+++ b/libraries/PCF8574/examples/buttonRead/buttonRead.ino
@@ -38,8 +38,14 @@ unsigned int blinkMillis;
 unsigned int buttonMillis;
 
 
-void setup() {
+void setup()
+{
   Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("PCF8574_LIB_VERSION: ");
+  Serial.println(PCF8574_LIB_VERSION);
+  
+  Wire.begin();
   pcf20.begin();
   
   pinMode(onboardLed, OUTPUT);
@@ -50,25 +56,25 @@ void loop() {
   static bool state;
   unsigned int currentMillis = millis();
   
-  //Limit button read to 20 times a second
-  //Fast enough for most buttons 
-  //but this way you don't have a dimmer output because it's blanked during button read
-  //a read takes 460us t 16Mhz Arduino and normal I2C speed.
-  if(currentMillis - buttonMillis >= 50){
+  //  Limit button read to 20 times a second
+  //  Fast enough for most buttons 
+  //  but this way you don't have a dimmer output because it's blanked during button read
+  //  a read takes 460us t 16Mhz Arduino and normal I2C speed.
+  if ((currentMillis - buttonMillis) >= 50) {
     buttonMillis = currentMillis;
     
-    if(state != pcf20.readButton(PcfButtonLedPin)){
-      if(state){
-        //toggle the LED
+    if (state != pcf20.readButton(PcfButtonLedPin)) {
+      if( state) {
+        //  toggle the LED
         digitalWrite(onboardLed, !digitalRead(onboardLed));
       }
       state = !state;
     }
   }
   
-  //Lets blink the same output
-  if(currentMillis - blinkMillis >= 500){
-    //Update time
+  //  Lets blink the same output
+  if ((currentMillis - blinkMillis) >= 500) {
+    //  Update time
     blinkMillis = currentMillis;
     
     pcf20.toggle(PcfButtonLedPin);
@@ -77,5 +83,5 @@ void loop() {
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/examples/buttonRead8/buttonRead8.ino b/libraries/PCF8574/examples/buttonRead8/buttonRead8.ino
index 10d55022..4aad5be4 100644
--- a/libraries/PCF8574/examples/buttonRead8/buttonRead8.ino
+++ b/libraries/PCF8574/examples/buttonRead8/buttonRead8.ino
@@ -39,8 +39,14 @@ unsigned int blinkMillis;
 unsigned int buttonMillis;
 
 
-void setup() {
+void setup()
+{
   Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("PCF8574_LIB_VERSION: ");
+  Serial.println(PCF8574_LIB_VERSION);
+  
+  Wire.begin();
   pcf20.begin();
   
   pinMode(onboardLed, OUTPUT);
@@ -61,7 +67,7 @@ void loop() {
   //  Fast enough for most buttons 
   //  but this way you don't have a dimmer output because it's blanked during button read
   //  a read takes 460us t 16Mhz Arduino and normal I2C speed.
-  if(currentMillis - buttonMillis >= 50){
+  if ((currentMillis - buttonMillis) >= 50) {
     buttonMillis = currentMillis;
     
     //  read all states but only force PcfButtonLedPin HIGH during the 
@@ -69,11 +75,11 @@ void loop() {
     //  Alternatively the mask could have been set with setButtonMask().
     //  Then the mask can be omitted here. See setup()
     //  byte inputStates = pcf20.readButton8(_BV(PcfButtonLedPin));
-    byte inputStates = pcf20.readButton8(1 << PcfButtonLedPin);      // Keep Arduino-CI happy
+    byte inputStates = pcf20.readButton8(1 << PcfButtonLedPin);      //  Keep Arduino-CI happy
     
     //  check the bit of PcfButtonLedPin
-    if(state != bitRead(inputStates, PcfButtonLedPin)){
-      if(state){
+    if (state != bitRead(inputStates, PcfButtonLedPin)) {
+      if (state) {
         //  toggle the LED
         digitalWrite(onboardLed, !digitalRead(onboardLed));
       }
@@ -82,7 +88,7 @@ void loop() {
   }
   
   //  Lets blink the same output
-  if(currentMillis - blinkMillis >= 500){
+  if ((currentMillis - blinkMillis) >= 500) {
     //  Update time
     blinkMillis = currentMillis;
     
@@ -93,5 +99,5 @@ void loop() {
 }
 
 
-// -- END OF FILE --
+//  -- END OF FILE --
 
diff --git a/libraries/PCF8574/library.json b/libraries/PCF8574/library.json
index b54b8e2b..9ab5b515 100644
--- a/libraries/PCF8574/library.json
+++ b/libraries/PCF8574/library.json
@@ -15,7 +15,7 @@
     "type": "git",
     "url": "https://github.com/RobTillaart/PCF8574.git"
   },
-  "version": "0.3.9",
+  "version": "0.4.0",
   "license": "MIT",
   "frameworks": "*",
   "platforms": "*",
diff --git a/libraries/PCF8574/library.properties b/libraries/PCF8574/library.properties
index 45b93406..ca2edad9 100644
--- a/libraries/PCF8574/library.properties
+++ b/libraries/PCF8574/library.properties
@@ -1,5 +1,5 @@
 name=PCF8574
-version=0.3.9
+version=0.4.0
 author=Rob Tillaart <rob.tillaart@gmail.com>
 maintainer=Rob Tillaart <rob.tillaart@gmail.com>
 sentence=Arduino library for PCF8574 - 8 channel I2C IO expander
diff --git a/libraries/PCF8574/test/unit_test_001.cpp b/libraries/PCF8574/test/unit_test_001.cpp
index 0aee909a..79116b40 100644
--- a/libraries/PCF8574/test/unit_test_001.cpp
+++ b/libraries/PCF8574/test/unit_test_001.cpp
@@ -55,6 +55,7 @@ unittest(test_begin)
 {
   PCF8574 PCF(0x38);
 
+  Wire.begin();
   PCF.begin();
 
   int readValue = PCF.read8();
@@ -70,6 +71,7 @@ unittest(test_read)
   PCF8574 PCF(0x38);
   int readValue;
 
+  Wire.begin();
   PCF.begin();
   for (int i = 0; i < 8; i++)
   {
@@ -92,7 +94,9 @@ unittest(test_address)
 {
   PCF8574 PCF(0x38);
 
-  // incorrect in test environment.
+  Wire.begin();
+
+  //  incorrect in test environment.
   assertTrue(PCF.begin());
   assertTrue(PCF.isConnected());
   assertEqual(0x38, PCF.getAddress());