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126 lines
3.2 KiB
126 lines
3.2 KiB
/* |
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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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