126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
/*
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* mcp3422.c:
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* Extend wiringPi with the MCP3422/3/4 I2C ADC chip
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* This code assumes single-ended mode only.
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* Tested on actual hardware: 20th Feb 2016.
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* Copyright (c) 2013-2016 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 <unistd.h>
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#include <stdint.h>
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#include <fcntl.h>
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#include <sys/ioctl.h>
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#include <wiringPi.h>
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#include <wiringPiI2C.h>
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#include "mcp3422.h"
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/*
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* waitForConversion:
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* Common code to wait for the ADC to finish conversion
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*********************************************************************************
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*/
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void waitForConversion (int fd, unsigned char *buffer, int n)
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{
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for (;;)
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{
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if ( read (fd, buffer, n) ){;}
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if ((buffer [n-1] & 0x80) == 0)
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break ;
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delay (1) ;
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}
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}
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/*
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* myAnalogRead:
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* Read a channel from the device
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*********************************************************************************
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*/
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int myAnalogRead (struct wiringPiNodeStruct *node, int chan)
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{
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unsigned char config ;
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unsigned char buffer [4] ;
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int value = 0 ;
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int realChan = (chan & 3) - node->pinBase ;
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// One-shot mode, trigger plus the other configs.
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config = 0x80 | (realChan << 5) | (node->data0 << 2) | (node->data1) ;
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wiringPiI2CWrite (node->fd, config) ;
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switch (node->data0) // Sample rate
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{
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case MCP3422_SR_3_75: // 18 bits
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waitForConversion (node->fd, &buffer [0], 4) ;
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value = ((buffer [0] & 3) << 16) | (buffer [1] << 8) | buffer [2] ;
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break ;
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case MCP3422_SR_15: // 16 bits
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waitForConversion (node->fd, buffer, 3) ;
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value = (buffer [0] << 8) | buffer [1] ;
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break ;
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case MCP3422_SR_60: // 14 bits
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waitForConversion (node->fd, buffer, 3) ;
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value = ((buffer [0] & 0x3F) << 8) | buffer [1] ;
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break ;
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case MCP3422_SR_240: // 12 bits - default
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waitForConversion (node->fd, buffer, 3) ;
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value = ((buffer [0] & 0x0F) << 8) | buffer [1] ;
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break ;
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}
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return value ;
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}
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/*
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* mcp3422Setup:
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* Create a new wiringPi device node for the mcp3422
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*********************************************************************************
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*/
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int mcp3422Setup (int pinBase, int i2cAddress, int sampleRate, int gain)
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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->data0 = sampleRate ;
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node->data1 = gain ;
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node->analogRead = myAnalogRead ;
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return TRUE ;
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}
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