Diff: DS18S20.cpp

Revision:

0:21c0c97a5d7c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DS18S20.cpp	Thu Feb 03 12:10:20 2011 +0000
@@ -0,0 +1,55 @@
+/*
+* DS18S20. Maxim DS18S20 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 "DS18S20.h"
+#include "DebugTrace.h"
+
+DebugTrace pc_ds18S20(ON, TO_SERIAL);
+
+DS18S20::DS18S20(bool crcOn, bool useAddr, bool parasitic, PinName pin) : 
+    OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18S20_ID)
+{
+}
+
+float DS18S20::calculateTemperature(BYTE* data)
+{    
+    // DS18S20 basic resolution is always 9 bits, which can be enhanced as follows
+    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;
+    }
+                 
+    float readTemp = (float)read_temp/2 ;            // divide by 2
+    pc_ds18S20.traceOut("TEMP_READ: %f \r\n", readTemp);     // 9 bit resolution value
+               
+    // convert to real temperature
+    float tempCount = float(data[COUNT_PER_DEG_BYTE] - data[COUNT_REMAIN_BYTE])/(float)data[COUNT_PER_DEG_BYTE];        
+    float realTemp = (readTemp - 0.25) + tempCount;        
+    pc_ds18S20.traceOut("Temperature: %f \r\n", realTemp);   // enhanced resolution value
+    
+    return realTemp;
+}
\ No newline at end of file