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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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+
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+#include <wiringPi.h>
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+#include <wiringPiSPI.h>
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+
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+#include "max31855.h"
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+
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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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+
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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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+
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+ wiringPiSPIDataRW (node->fd, (unsigned char *)&spiData, 4) ;
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+
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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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+
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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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+
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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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+
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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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+
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+ node = wiringPiNewNode (pinBase, 2) ;
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+
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+ node->fd = spiChannel ;
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+ node->analogRead = myAnalogRead ;
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+
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+ return 0 ;
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+}
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