Diff: DS18B20.cpp

Revision:

0:ad90c2e86a63

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DS18B20.cpp	Sun Apr 17 17:27:20 2011 +0000
@@ -0,0 +1,95 @@
+/*
+* DS18B20. Maxim DS18B20 One-Wire Thermometer.
+* Uses the OneWireCRC library.
+*
+* Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>
+*
+* This file is part of OneWireThermometer.
+*
+* OneWireThermometer is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* OneWireThermometer 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 General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with OneWireThermometer.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "DS18B20.h"
+#include "DebugTrace.h"
+
+DebugTrace pc_ds18B20(OFF, TO_SERIAL);
+
+DS18B20::DS18B20(PinName pin,bool crcOn, bool useAddr, bool parasitic, unsigned char *Address) :
+        OneWireThermometer(pin, crcOn, useAddr, parasitic, DS18B20_ID, Address) {
+}
+
+void DS18B20::setResolution(eResolution resln) {
+    // as the write to the configuration register involves a write to the
+    // high and low alarm bytes, need to read these registers first
+    // and copy them back on the write
+
+    BYTE read_data[THERMOM_SCRATCHPAD_SIZE];
+    BYTE write_data[ALARM_CONFIG_SIZE];
+
+    if (readAndValidateData(read_data)) {
+        // copy alarm and config data to write data
+        for (int k = 2; k < 5; k++) {
+            write_data[k - 2] = read_data[k];
+        }
+        int config = write_data[2];
+        config &= 0x9F;
+        config ^= (resln << 5);
+        write_data[2] = config;
+
+        resetAndAddress();
+        oneWire.writeByte(DS18X20_WRITESCRATCH);
+        for (int k = 0; k < 3; k++) {
+            oneWire.writeByte(write_data[k]);
+        }
+
+        // remember it so we can use the correct delay in reading the temperature
+        // for parasitic power
+        _resolution = resln;
+    }
+}
+
+float DS18B20::calculateTemperature(BYTE* data) {
+    bool signBit = false;
+    if (data[TEMPERATURE_MSB] & 0x80) signBit = true;
+
+    int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];
+    if (signBit) {
+        read_temp = (read_temp ^ 0xFFFF) + 1;    // two's complement
+        read_temp *= -1;
+    }
+
+    int resolution = (data[CONFIG_REG_BYTE] & 0x60) >> 5; // mask off bits 6,5 and move to 1,0
+    switch (resolution) {
+        case nineBit:    // 0.5 deg C increments
+            read_temp &= 0xFFF8;                // bits 2,1,0 are undefined
+            pc_ds18B20.traceOut("9 bit resolution ...\r\n");
+            break;
+        case tenBit:     // 0.25 deg C increments
+            read_temp &= 0xFFFC;                // bits 1,0 are undefined
+            pc_ds18B20.traceOut("10 bit resolution ...\r\n");
+            break;
+        case elevenBit:  // 0.125 deg C increments
+            read_temp &= 0xFFFE;                // bit 0 is undefined
+            pc_ds18B20.traceOut("11 bit resolution ...\r\n");
+            break;
+        case twelveBit:  // 0.0625 deg C increments
+            pc_ds18B20.traceOut("12 bit resolution ...\r\n");
+            break;
+    }
+    float realTemp = (float)read_temp/16 ;
+
+    pc_ds18B20.traceOut("TEMP_READ/REAL TEMP: %f \r\n", realTemp);
+
+    return realTemp;
+}
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