91 lines
2.5 KiB
C
91 lines
2.5 KiB
C
/*
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* pcf8591.c:
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* Extend wiringPi with the PCF8591 I2C GPIO Analog expander chip
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* The chip has 1 8-bit DAC and 4 x 8-bit ADCs
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* Copyright (c) 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 <unistd.h>
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#include "wiringPi.h"
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#include "wiringPiI2C.h"
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#include "pcf8591.h"
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/*
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* myAnalogWrite:
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*********************************************************************************
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*/
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static void myAnalogWrite (struct wiringPiNodeStruct *node, UNU int pin, int value)
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{
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unsigned char b [2] ;
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b [0] = 0x40 ;
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b [1] = value & 0xFF ;
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write (node->fd, b, 2) ;
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}
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/*
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* myAnalogRead:
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*********************************************************************************
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*/
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static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
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{
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int x ;
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wiringPiI2CWrite (node->fd, 0x40 | ((pin - node->pinBase) & 3)) ;
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x = wiringPiI2CRead (node->fd) ; // Throw away the first read
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x = wiringPiI2CRead (node->fd) ;
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return x ;
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}
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/*
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* pcf8591Setup:
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* Create a new instance of a PCF8591 I2C GPIO interface. We know it
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* has 4 pins, (4 analog inputs and 1 analog output which we'll shadow
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* input 0) so all we need to know here is the I2C address and the
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* user-defined pin base.
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*********************************************************************************
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*/
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int pcf8591Setup (const int pinBase, const int i2cAddress)
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{
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int fd ;
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struct wiringPiNodeStruct *node ;
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if ((fd = wiringPiI2CSetup (i2cAddress)) < 0)
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return FALSE ;
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node = wiringPiNewNode (pinBase, 4) ;
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node->fd = fd ;
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node->analogRead = myAnalogRead ;
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node->analogWrite = myAnalogWrite ;
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return TRUE ;
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}
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