127 lines
3.2 KiB
C
127 lines
3.2 KiB
C
/*
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* pcf8574.c:
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* Extend wiringPi with the PCF8574 I2C GPIO expander chip
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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 <stdio.h>
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#include <pthread.h>
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#include "wiringPi.h"
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#include "wiringPiI2C.h"
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#include "pcf8574.h"
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/*
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* myPinMode:
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* The PCF8574 is an odd chip - the pins are effectively bi-directional,
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* however the pins should be drven high when used as an input pin...
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* So, we're effectively copying digitalWrite...
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*********************************************************************************
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*/
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static void myPinMode (struct wiringPiNodeStruct *node, int pin, int mode)
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{
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int bit, old ;
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bit = 1 << ((pin - node->pinBase) & 7) ;
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old = node->data2 ;
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if (mode == OUTPUT)
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old &= (~bit) ; // Write bit to 0
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else
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old |= bit ; // Write bit to 1
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wiringPiI2CWrite (node->fd, old) ;
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node->data2 = old ;
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}
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/*
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* myDigitalWrite:
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*********************************************************************************
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*/
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static void myDigitalWrite (struct wiringPiNodeStruct *node, int pin, int value)
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{
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int bit, old ;
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bit = 1 << ((pin - node->pinBase) & 7) ;
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old = node->data2 ;
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if (value == LOW)
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old &= (~bit) ;
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else
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old |= bit ;
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wiringPiI2CWrite (node->fd, old) ;
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node->data2 = old ;
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}
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/*
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* myDigitalRead:
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*********************************************************************************
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*/
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static int myDigitalRead (struct wiringPiNodeStruct *node, int pin)
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{
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int mask, value ;
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mask = 1 << ((pin - node->pinBase) & 7) ;
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value = wiringPiI2CRead (node->fd) ;
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if ((value & mask) == 0)
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return LOW ;
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else
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return HIGH ;
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}
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/*
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* pcf8574Setup:
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* Create a new instance of a PCF8574 I2C GPIO interface. We know it
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* has 8 pins, 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 pcf8574Setup (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, 8) ;
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node->fd = fd ;
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node->pinMode = myPinMode ;
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node->digitalRead = myDigitalRead ;
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node->digitalWrite = myDigitalWrite ;
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node->data2 = wiringPiI2CRead (fd) ;
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return TRUE ;
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}
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