100 lines
2.7 KiB
C
100 lines
2.7 KiB
C
/*
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* max31855.c:
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* Extend wiringPi with the max31855 SPI Analog to Digital convertor
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* Copyright (c) 2012-2015 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 <byteswap.h>
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#include <stdint.h>
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#include <wiringPi.h>
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#include <wiringPiSPI.h>
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#include "max31855.h"
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static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
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{
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uint32_t spiData ;
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int temp ;
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int chan = pin - node->pinBase ;
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wiringPiSPIDataRW (node->fd, (unsigned char *)&spiData, 4) ;
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spiData = __bswap_32(spiData) ;
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switch (chan)
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{
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case 0: // Existing read - return raw value * 4
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spiData >>= 18 ;
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temp = spiData & 0x1FFF ; // Bottom 13 bits
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if ((spiData & 0x2000) != 0) // Negative
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temp = -temp ;
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return temp ;
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case 1: // Return error bits
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return spiData & 0x7 ;
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case 2: // Return temp in C * 10
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spiData >>= 18 ;
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temp = spiData & 0x1FFF ; // Bottom 13 bits
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if ((spiData & 0x2000) != 0) // Negative
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temp = -temp ;
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return (int)((((double)temp * 25) + 0.5) / 10.0) ;
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case 3: // Return temp in F * 10
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spiData >>= 18 ;
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temp = spiData & 0x1FFF ; // Bottom 13 bits
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if ((spiData & 0x2000) != 0) // Negative
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temp = -temp ;
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return (int)((((((double)temp * 0.25 * 9.0 / 5.0) + 32.0) * 100.0) + 0.5) / 10.0) ;
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default: // Who knows...
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return 0 ;
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}
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}
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/*
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* max31855Setup:
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* Create a new wiringPi device node for an max31855 on the Pi's
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* SPI interface.
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*********************************************************************************
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*/
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int max31855Setup (const int pinBase, int spiChannel)
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{
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struct wiringPiNodeStruct *node ;
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if (wiringPiSPISetup (spiChannel, 5000000) < 0) // 5MHz - prob 4 on the Pi
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return FALSE ;
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node = wiringPiNewNode (pinBase, 4) ;
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node->fd = spiChannel ;
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node->analogRead = myAnalogRead ;
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return TRUE ;
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}
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