mcp4802.c
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/*
* mcp4802.c:
* Extend wiringPi with the MCP4802 SPI Digital to Analog convertor
* Copyright (c) 2012-2013 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 <wiringPi.h>
#include <wiringPiSPI.h>
#include "mcp4802.h"
/*
* myAnalogWrite:
* Write analog value on the given pin
*********************************************************************************
*/
static void myAnalogWrite (struct wiringPiNodeStruct *node, int pin, int value)
{
unsigned char spiData [2] ;
unsigned char chanBits, dataBits ;
int chan = pin - node->pinBase ;
if (chan == 0)
chanBits = 0x30 ;
else
chanBits = 0xB0 ;
chanBits |= ((value >> 4) & 0x0F) ;
dataBits = ((value << 4) & 0xF0) ;
spiData [0] = chanBits ;
spiData [1] = dataBits ;
wiringPiSPIDataRW (node->fd, spiData, 2) ;
}
/*
* mcp4802Setup:
* Create a new wiringPi device node for an mcp4802 on the Pi's
* SPI interface.
*********************************************************************************
*/
int mcp4802Setup (const int pinBase, int spiChannel)
{
struct wiringPiNodeStruct *node ;
if (wiringPiSPISetup (spiChannel, 1000000) < 0)
return -1 ;
node = wiringPiNewNode (pinBase, 2) ;
node->fd = spiChannel ;
node->analogWrite = myAnalogWrite ;
return 0 ;
}