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/*
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 * mcp4802.c:
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 *        Extend wiringPi with the MCP4802 SPI Digital to Analog convertor
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 *        Copyright (c) 2012-2013 Gordon Henderson
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 ***********************************************************************
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 * This file is part of wiringPi:
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 *        https://projects.drogon.net/raspberry-pi/wiringpi/
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 *
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 *    wiringPi is free software: you can redistribute it and/or modify
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 *    it under the terms of the GNU Lesser General Public License as
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 *    published by the Free Software Foundation, either version 3 of the
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 *    License, or (at your option) any later version.
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 *
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 *    wiringPi is distributed in the hope that it will be useful,
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 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
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 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 *    GNU Lesser General Public License for more details.
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 *
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 *    You should have received a copy of the GNU Lesser General Public
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 *    License along with wiringPi.
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 *    If not, see <http://www.gnu.org/licenses/>.
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 ***********************************************************************
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 */
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#include <wiringPi.h>
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#include <wiringPiSPI.h>
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#include "mcp4802.h"
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/*
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 * myAnalogWrite:
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 *        Write analog value on the given pin
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 *********************************************************************************
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 */
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static void myAnalogWrite (struct wiringPiNodeStruct *node, int pin, int value)
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{
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  unsigned char spiData [2] ;
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  unsigned char chanBits, dataBits ;
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  int chan = pin - node->pinBase ;
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  if (chan == 0)
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    chanBits = 0x30 ;
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  else
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    chanBits = 0xB0 ;
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  chanBits |= ((value >> 4) & 0x0F) ;
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  dataBits  = ((value << 4) & 0xF0) ;
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  spiData [0] = chanBits ;
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  spiData [1] = dataBits ;
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  wiringPiSPIDataRW (node->fd, spiData, 2) ;
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}
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/*
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 * mcp4802Setup:
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 *        Create a new wiringPi device node for an mcp4802 on the Pi's
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 *        SPI interface.
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 *********************************************************************************
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 */
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int mcp4802Setup (const int pinBase, int spiChannel)
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{
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  struct wiringPiNodeStruct *node ;
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  if (wiringPiSPISetup (spiChannel, 1000000) < 0)
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    return FALSE ;
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  node = wiringPiNewNode (pinBase, 2) ;
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  node->fd          = spiChannel ;
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  node->analogWrite = myAnalogWrite ;
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  return TRUE ;
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}