PCF8574 output pin initialization parameter

IO_PCA9554.h

@@ -0,0 +1,101 @@
+/*
+ *  © 2025, 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/TCA9554 8-bit I/O expander (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) 
+  {
+    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 & TCA9554, Interrupt is always enabled for raising and falling edge
+    uint8_t temp = ~(_portMode & _portInUse);
+    I2CManager.write(_I2CAddress, 2, REG_CONF_P0, temp);    
+  }
+  void _readGpioPort(bool immediate) override {
+    if (immediate) {
+      uint8_t buffer[1];
+      I2CManager.read(_I2CAddress, buffer, 1, 1, REG_INPUT_P0);
+      _portInputState = buffer[0];
+    } 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[1];
+  uint8_t outputBuffer[1];
+ 
+
+  enum {
+    REG_INPUT_P0 = 0x00,
+    REG_OUTPUT_P0 = 0x01,
+    REG_POL_INV_P0 = 0x02,
+    REG_CONF_P0 = 0x03,
+  };
+
+};
+
+#endif

IO_PCF8574.h

@@ -1,4 +1,5 @@
 /*
+ *  © 2025 Herb Morton
  *  © 2022 Paul M Antoine
  *  © 2021, Neil McKechnie. All rights reserved.
  *  
@@ -43,15 +44,21 @@
 
 class PCF8574 : public GPIOBase<uint8_t> {
 public:
-  static void create(VPIN firstVpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1) {
+  static void create(VPIN firstVpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1, int initPortState=-1) {
-    if (checkNoOverlap(firstVpin, nPins, i2cAddress)) new PCF8574(firstVpin, nPins, i2cAddress, interruptPin);
+    if (checkNoOverlap(firstVpin, nPins, i2cAddress)) new PCF8574(firstVpin, nPins, i2cAddress, interruptPin, initPortState);
   }
 
 private:
-  PCF8574(VPIN firstVpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1)
+  PCF8574(VPIN firstVpin, uint8_t nPins, I2CAddress i2cAddress, int interruptPin=-1, int initPortState=-1)
     : GPIOBase<uint8_t>((FSH *)F("PCF8574"), firstVpin, nPins, i2cAddress, interruptPin) 
   {
     requestBlock.setReadParams(_I2CAddress, inputBuffer, 1);
+    if (initPortState>=0) {
+      _portMode = 255;         // set all pins to output mode
+      _portInUse = 255;        // 8 ports in use 
+      _portOutputState = initPortState;  // initialize pins low-high 0-255
+      I2CManager.write(_I2CAddress, 1, initPortState);
+    }
   }
   
   // The PCF8574 handles inputs by applying a weak pull-up when output is driven to '1'.

myHal.cpp_example.txt

@@ -146,7 +146,14 @@ void halSetup() {
 
   //PCF8574::create(200, 8, 0x23, 40);
 
+  // Alternative form to initialize 8 pins as output
+  //  INT pin -1, when INT is not used
 
+  //PCF8574::create(200, 8, 0x23, -1, 255);  8 pins High
+  //PCF8574::create(200, 8, 0x23, -1, 0);    8 pins Low
+  //PCF8574::create(200, 8, 0x23, -1, 0b11000010);  
+  //                       pins listed sequentially from 7 to 0
+  
   //=======================================================================
   // The following directive defines a PCF8575 16-port I2C GPIO Extender module.
   //=======================================================================

version.h

@@ -3,7 +3,9 @@
 
 #include "StringFormatter.h"
 
-#define VERSION "5.5.25"
+#define VERSION "5.5.27"
+// 5.5.27 - PCF8574 output pin initialization parameter
+// 5.5.26 - PCA9554 and TCA9554/9534 I2C 8-bit GPIO expander drivers
 // 5.2.25 - IO_Bitmap and assicated Exrail macros
 // 5.5.24 - SensorCAM in I2C scan and automatically setClock
 // 5.5.23 - Reminder loop Idle packet optimization