mcp3422.c
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/*
* mcp3422.c:
* Extend wiringPi with the MCP3422 I2C ADC chip
* Also works for the MCP3423 and MCP3224 (4 channel) chips
* Copyright (c) 2013 Gordon Henderson
***********************************************************************
* This file is part of wiringPi:
* https://projects.drogon.net/raspberry-pi/wiringpi/
*
* wiringPi is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* wiringPi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with wiringPi.
* If not, see <http://www.gnu.org/licenses/>.
***********************************************************************
*/
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/spi/spidev.h>
#include <wiringPi.h>
#include <wiringPiI2C.h>
#include "mcp3422.h"
/*
* myAnalogRead:
* Read a channel from the device
*********************************************************************************
*/
int myAnalogRead (struct wiringPiNodeStruct *node, int chan)
{
unsigned char config ;
unsigned char buffer [4] ;
int value = 0 ;
// One-shot mode, trigger plus the other configs.
config = 0x80 | ((chan - node->pinBase) << 5) | (node->data0 << 2) | (node->data1) ;
wiringPiI2CWrite (node->fd, config) ;
switch (node->data0) // Sample rate
{
case MCP3422_SR_3_75: // 18 bits
delay (270) ;
read (node->fd, buffer, 4) ;
value = ((buffer [0] & 3) << 16) | (buffer [1] << 8) | buffer [0] ;
break ;
case MCP3422_SR_15: // 16 bits
delay ( 70) ;
read (node->fd, buffer, 3) ;
value = (buffer [0] << 8) | buffer [1] ;
break ;
case MCP3422_SR_60: // 14 bits
delay ( 17) ;
read (node->fd, buffer, 3) ;
value = ((buffer [0] & 0x3F) << 8) | buffer [1] ;
break ;
case MCP3422_SR_240: // 12 bits
delay ( 5) ;
read (node->fd, buffer, 3) ;
value = ((buffer [0] & 0x0F) << 8) | buffer [0] ;
break ;
}
return value ;
}
/*
* mcp3422Setup:
* Create a new wiringPi device node for the mcp3422
*********************************************************************************
*/
int mcp3422Setup (int pinBase, int i2cAddress, int sampleRate, int gain)
{
int fd ;
struct wiringPiNodeStruct *node ;
if ((fd = wiringPiI2CSetup (i2cAddress)) < 0)
return fd ;
node = wiringPiNewNode (pinBase, 4) ;
node->data0 = sampleRate ;
node->data1 = gain ;
node->analogRead = myAnalogRead ;
return 0 ;
}