text: /*
   * mcp3422.c:
   *	Extend wiringPi with the MCP3422/3/4 I2C ADC chip
   *	This code assumes single-ended mode only.
   *	Tested on actual hardware: 20th Feb 2016.
   *	Copyright (c) 2013-2016 Gordon Henderson
   ***********************************************************************
   * This file is part of wiringPi:
   *	https://projects.drogon.net/raspberry-pi/wiringpi/
   *
   *    wiringPi is free software: you can redistribute it and/or modify
   *    it under the terms of the GNU Lesser General Public License as
   *    published by the Free Software Foundation, either version 3 of the
   *    License, or (at your option) any later version.
   *
   *    wiringPi 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 Lesser General Public License for more details.
   *
   *    You should have received a copy of the GNU Lesser General Public
   *    License along with wiringPi.
   *    If not, see <http://www.gnu.org/licenses/>.
   ***********************************************************************
   */
  
  
  #include <stdio.h>
  #include <unistd.h>
  #include <stdint.h>
  #include <fcntl.h>
  #include <sys/ioctl.h>
  
  #include "wiringPi.h"
  #include "wiringPiI2C.h"
  
  #include "mcp3422.h"
  
  
  /*
   * waitForConversion:
   *	Common code to wait for the ADC to finish conversion
   *********************************************************************************
   */
  
  void waitForConversion (int fd, unsigned char *buffer, int n)
  {
    for (;;)
    {
      read (fd, buffer, n) ;
      if ((buffer [n-1] & 0x80) == 0)
        break ;
      delay (1) ;
    }
  }
  
  /*
   * myAnalogRead:
   *	Read a channel from the device
   *********************************************************************************
   */
  
  int myAnalogRead (struct wiringPiNodeStruct *node, int chan)
  {
    unsigned char config ;
    unsigned char buffer [4] ;
    int value = 0 ;
    int realChan = (chan & 3) - node->pinBase ;
  
  // One-shot mode, trigger plus the other configs.
  
    config = 0x80 | (realChan << 5) | (node->data0 << 2) | (node->data1) ;
    
    wiringPiI2CWrite (node->fd, config) ;
  
    switch (node->data0)	// Sample rate
    {
      case MCP3422_SR_3_75:			// 18 bits
        waitForConversion (node->fd, &buffer [0], 4) ;
        value = ((buffer [0] & 3) << 16) | (buffer [1] << 8) | buffer [2] ;
        break ;
  
      case MCP3422_SR_15:				// 16 bits
        waitForConversion (node->fd, buffer, 3) ;
        value = (buffer [0] << 8) | buffer [1] ;
        break ;
  
      case MCP3422_SR_60:				// 14 bits
        waitForConversion (node->fd, buffer, 3) ;
        value = ((buffer [0] & 0x3F) << 8) | buffer [1] ;
        break ;
  
      case MCP3422_SR_240:			// 12 bits - default
        waitForConversion (node->fd, buffer, 3) ;
        value = ((buffer [0] & 0x0F) << 8) | buffer [1] ;
        break ;
    }
  
    return value ;
  }
  
  
  /*
   * mcp3422Setup:
   *	Create a new wiringPi device node for the mcp3422
   *********************************************************************************
   */
  
  int mcp3422Setup (int pinBase, int i2cAddress, int sampleRate, int gain)
  {
    int fd ;
    struct wiringPiNodeStruct *node ;
  
    if ((fd = wiringPiI2CSetup (i2cAddress)) < 0)
      return FALSE ;
  
    node = wiringPiNewNode (pinBase, 4) ;
  
    node->fd         = fd ;
    node->data0      = sampleRate ;
    node->data1      = gain ;
    node->analogRead = myAnalogRead ;
  
    return TRUE ;
  }
  