diff --git a/IO_PCA9554.h b/IO_PCA9554.h
new file mode 100644
index 0000000..417c5d2
--- /dev/null
+++ b/IO_PCA9554.h
@@ -0,0 +1,110 @@
+/*
+ *  © 2024, Paul M. Antoine
+ *  © 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_pca9554_h
+#define io_pca9554_h
+
+#include "IO_GPIOBase.h"
+#include "FSH.h"
+
+/////////////////////////////////////////////////////////////////////////////////////////////////////
+/*
+ * IODevice subclass for PCA9554 and TCA9554/9534 8-bit I/O expanders (NXP & Texas Instruments).
+ */
+ 
+class PCA9554 : public GPIOBase<uint8_t> {
+public:
+  static void create(VPIN vpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1) {
+    if (checkNoOverlap(vpin, nPins, i2cAddress)) new PCA9554(vpin,nPins, i2cAddress, interruptPin);
+  }
+
+private:  
+  // Constructor
+  PCA9554(VPIN vpin, uint8_t nPins, I2CAddress I2CAddress, int interruptPin=-1) 
+    : GPIOBase<uint8_t>((FSH *)F("PCA9554"), vpin, nPins, I2CAddress, interruptPin) 
+  {
+    if (nPins > 8)
+      DIAG(F("PCA9554 nPins %d larger than allowed!"));
+    requestBlock.setRequestParams(_I2CAddress, inputBuffer, sizeof(inputBuffer),
+                                  outputBuffer, sizeof(outputBuffer));
+    outputBuffer[0] = REG_INPUT_P0;
+  }
+  void _writeGpioPort() override {
+    I2CManager.write(_I2CAddress, 2, REG_OUTPUT_P0, _portOutputState);
+  }
+  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.
+    // PCA9554 & TCA9555, Interrupt is always enabled for raising and falling edge
+    uint16_t temp = ~(_portMode & _portInUse);
+    I2CManager.write(_I2CAddress, 2, REG_CONF_P0, temp);    
+  }
+  void _readGpioPort(bool immediate) override {
+    if (immediate) {
+      uint8_t buffer[2];
+      I2CManager.read(_I2CAddress, buffer, 1, 1, REG_INPUT_P0);
+      _portInputState = buffer[0];
+      /* PCA9554 Int bug fix, from PCA9554 datasheet: "must change command byte to something besides 00h 
+       * after a Read operation to the PCA9554 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, 1, 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 = inputBuffer[0];
+    else  
+      _portInputState = 0xff;
+  }
+
+  void _setupDevice() override {
+    // HAL API calls
+    _writePortModes();
+    _writePullups();
+    _writeGpioPort();
+  }
+ 
+  uint8_t inputBuffer[2];
+  uint8_t outputBuffer[1];
+ 
+
+  enum {
+    REG_INPUT_P0 = 0x00,
+    REG_OUTPUT_P0 = 0x01,
+    REG_POL_INV_P0 = 0x02,
+    REG_CONF_P0 = 0x03,
+  };
+
+};
+
+#endif