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/* |
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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) 2012-2013 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 <wiringPi.h> |
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#include <wiringPiSPI.h> |
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#include "max31855.h" |
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/* |
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* myAnalogRead: |
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* Return the analog value of the given pin |
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* Note: The chip really only has one read "channel", but we're faking it |
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* here so we can read the error registers. Channel 0 will be the data |
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* channel, and 1 is the error register code. |
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* Note: Temperature returned is temp in C * 4, so divide result by 4 |
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********************************************************************************* |
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*/ |
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static int myAnalogRead (struct wiringPiNodeStruct *node, int pin) |
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{ |
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unsigned int 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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if (chan == 0) // Read temp in C |
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{ |
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spiData >>= 18 ; |
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temp = spiData & 0x3FFF ; // 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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} |
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else // Return error bits |
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return spiData & 0x7 ; |
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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 -1 ; |
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node = wiringPiNewNode (pinBase, 2) ; |
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node->fd = spiChannel ; |
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node->analogRead = myAnalogRead ; |
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return 0 ; |
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} |