CommandStation-EX/IO_MCP23017.h

/*
 *  © 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_mcp23017_h
#define io_mcp23017_h

#include "IO_GPIOBase.h"
#include "FSH.h"

/////////////////////////////////////////////////////////////////////////////////////////////////////
/*
 * IODevice subclass for MCP23017 16-bit I/O expander.
 */
 
class MCP23017 : public GPIOBase<uint16_t> {
public:
  static void create(VPIN vpin, int nPins, uint8_t I2CAddress, int interruptPin=-1) {
    new MCP23017(vpin, min(nPins,16), I2CAddress, interruptPin);
  }
  
  // Constructor
  MCP23017(VPIN vpin, int nPins, uint8_t I2CAddress, int interruptPin=-1) 
    : GPIOBase<uint16_t>((FSH *)F("MCP23017"), vpin, nPins, I2CAddress, interruptPin) 
  {
    requestBlock.setRequestParams(_I2CAddress, inputBuffer, sizeof(inputBuffer),
      outputBuffer, sizeof(outputBuffer));
    outputBuffer[0] = REG_GPIOA;
  }

private:
  void _writeGpioPort() override {
    I2CManager.write(_I2CAddress, 3, REG_GPIOA, _portOutputState, _portOutputState>>8);
  }
  void _writePullups() override {
    // Set pullups only for in-use pins.  This prevents pullup being set for a pin that
    //  is intended for use as an output but hasn't been written to yet.
    uint16_t temp = _portPullup & _portInUse;
    I2CManager.write(_I2CAddress, 3, REG_GPPUA, temp, temp>>8);  
  }
  void _writePortModes() override {
    // Write 0 to IODIR for in-use pins that are outputs, 1 for others.
    uint16_t temp = ~(_portMode & _portInUse);
    I2CManager.write(_I2CAddress, 3, REG_IODIRA, temp, temp>>8);
    // Enable interrupt for in-use pins which are inputs (_portMode=0)
    temp = ~_portMode & _portInUse;
    I2CManager.write(_I2CAddress, 3, REG_INTCONA, 0x00, 0x00);
    I2CManager.write(_I2CAddress, 3, REG_GPINTENA, temp, temp>>8);
  }
  void _readGpioPort(bool immediate) override {
    if (immediate) {
      uint8_t buffer[2];
      I2CManager.read(_I2CAddress, buffer, 2, 1, REG_GPIOA);
      _portInputState = ((uint16_t)buffer[1]<<8) | 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 = ((uint16_t)inputBuffer[1]<<8) | inputBuffer[0];
    else  
      _portInputState = 0xffff;
  }

  void _setupDevice() override {
    // IOCON is set MIRROR=1, ODR=1 (open drain shared interrupt pin)
    I2CManager.write(_I2CAddress, 2, REG_IOCON, 0x44);
    _writePortModes();
    _writePullups();
    _writeGpioPort();
  }
 
  uint8_t inputBuffer[2];
  uint8_t outputBuffer[1];
 
  enum {
    REG_IODIRA = 0x00,
    REG_IODIRB = 0x01,
    REG_GPINTENA = 0x04,
    REG_GPINTENB = 0x05,
    REG_INTCONA = 0x08,
    REG_INTCONB = 0x09,
    REG_IOCON = 0x0A,
    REG_GPPUA = 0x0C,
    REG_GPPUB = 0x0D,
    REG_GPIOA = 0x12,
    REG_GPIOB = 0x13,
  };

};

#endif