diff --git a/IO_PCA9555.h b/IO_PCA9555.h
new file mode 100644
index 0000000..137e287
--- /dev/null
+++ b/IO_PCA9555.h
@@ -0,0 +1,112 @@
+/*
+ *  © 2021, Neil McKechnie. All rights reserved.
+ *  
+ *  This file is part of DCC++EX API
+ *
+ *  This is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  It is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef io_pca9555_h
+#define io_pca9555_h
+
+#include "IO_GPIOBase.h"
+#include "FSH.h"
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+/*
+ * IODevice subclass for PCA9555 16-bit I/O expander (NXP & Texas Instruments).
+ */
+ 
+class PCA9555 : public GPIOBase<uint16_t> {
+public:
+  static void create(VPIN vpin, int nPins, uint8_t I2CAddress, int interruptPin=-1) {
+    new PCA9555(vpin, min(nPins,16), I2CAddress, interruptPin);
+  }
+  
+  // Constructor
+  PCA9555(VPIN vpin, int nPins, uint8_t I2CAddress, int interruptPin=-1) 
+    : GPIOBase<uint16_t>((FSH *)F("PCA9555"), vpin, nPins, I2CAddress, interruptPin) 
+  {
+    requestBlock.setRequestParams(_I2CAddress, inputBuffer, sizeof(inputBuffer),
+      outputBuffer, sizeof(outputBuffer));
+    outputBuffer[0] = REG_INPUT_P0;
+  }
+
+private:
+  void _writeGpioPort() override {
+    I2CManager.write(_I2CAddress, 3, REG_OUTPUT_P0, _portOutputState, _portOutputState>>8);
+  }
+  void _writePullups() override {
+    // Do nothing, pull-ups are always in place for input ports
+    // This function is here for HAL GPIOBase API compatibilitiy
+      
+  }
+  void _writePortModes() override {
+    // Write 0 to REG_CONF_P0 & REG_CONF_P1 for in-use pins that are outputs, 1 for others.
+    // PCA9555 & TCA9555, Interrupt is always enabled for raising and falling edge
+    uint16_t temp = ~(_portMode & _portInUse);
+    I2CManager.write(_I2CAddress, 3, REG_CONF_P0, temp, temp>>8);    
+  }
+  void _readGpioPort(bool immediate) override {
+    if (immediate) {
+      uint8_t buffer[2];
+      I2CManager.read(_I2CAddress, buffer, 2, 1, REG_INPUT_P0);
+      _portInputState = ((uint16_t)buffer[1]<<8) | buffer[0];
+      /* PCA9555 Int bug fix, from PCA9555 datasheet: "must change command byte to something besides 00h 
+       * after a Read operation to the PCA9555 device or before reading from 
+       * another device"
+       * Recommended solution, read from REG_OUTPUT_P0, then do nothing with the received data
+       * Issue not seen during testing, uncomment if needed 
+       */
+      //I2CManager.read(_I2CAddress, buffer, 2, 1, REG_OUTPUT_P0);
+    } else {
+      // Queue new request
+      requestBlock.wait(); // Wait for preceding operation to complete
+      // Issue new request to read GPIO register
+      I2CManager.queueRequest(&requestBlock);
+    }
+  }
+  // This function is invoked when an I/O operation on the requestBlock completes.
+  void _processCompletion(uint8_t status) override {
+    if (status == I2C_STATUS_OK) 
+      _portInputState = ((uint16_t)inputBuffer[1]<<8) | inputBuffer[0];
+    else  
+      _portInputState = 0xffff;
+  }
+
+  void _setupDevice() override {
+    // HAL API calls
+    _writePortModes();
+    _writePullups();
+    _writeGpioPort();
+  }
+ 
+  uint8_t inputBuffer[2];
+  uint8_t outputBuffer[1];
+ 
+
+  enum {
+    REG_INPUT_P0 = 0x00,
+    REG_INPUT_P1 = 0x01,
+    REG_OUTPUT_P0 = 0x02,
+    REG_OUTPUT_P1 = 0x03,
+    REG_POL_INV_P0 = 0x04,
+    REG_POL_INV_P1 = 0x05,
+    REG_CONF_P0 = 0x06,
+    REG_CONF_P1 = 0x07,    
+  };
+
+};
+
+#endif
diff --git a/myHal.cpp_example.txt b/myHal.cpp_example.txt
index 32aa12e..fb5ef55 100644
--- a/myHal.cpp_example.txt
+++ b/myHal.cpp_example.txt
@@ -16,10 +16,13 @@
 #if !defined(IO_NO_HAL)
 
 // Include devices you need.
-#include "IODevice.h"
+#include "IODevice.h"     // Always recommended to include this
+
+// Optional includes, comment out if not in use
 #include "IO_HCSR04.h"    // Ultrasonic range sensor
 #include "IO_VL53L0X.h"   // Laser time-of-flight sensor
 #include "IO_DFPlayer.h"  // MP3 sound player
+#include "IO_PCA9555.h"   // PCA/TCA9555
 
 
 //==========================================================================
@@ -60,6 +63,33 @@ void halSetup() {
   //MCP23017::create(196, 16, 0x22, 40);
 
 
+  //=======================================================================
+  // The following directive defines an PCA9555 / TCA95555 16-port I2C GPIO Extender module.
+  //=======================================================================
+  // The parameters are: 
+  //   First Vpin=196
+  //   Number of VPINs=16 (numbered 196-211)
+  //   I2C address of module=0x22
+
+  //PCA9555::create(196, 16, 0x22);
+
+  // Alternative form, which allows the INT pin of the module to request a scan
+  // by pulling Arduino pin 22 to ground. Means that the I2C isn't being polled
+  // all the time, only when a change takes place. Multiple modules' INT pins
+  // may be connected to the same Arduino pin.
+
+  //PCA9555::create(196, 16, 0x22, 22);
+  
+
+  //=======================================================================
+  // The following directive defines an MCP23008 8-port I2C GPIO Extender module.
+  //=======================================================================
+  // The parameters are: 
+  //   First Vpin=300
+  //   Number of VPINs=8 (numbered 300-307)
+  //   I2C address of module=0x22
+
+
   //=======================================================================
   // The following directive defines an MCP23008 8-port I2C GPIO Extender module.
   //=======================================================================