max6675.cpp

00001 
00002 #include <mbed.h>
00003 #include "max6675.h"
00004 
00005 max6675::max6675(SPI& _spi, PinName _ncs) : spi(_spi), ncs(_ncs) {
00006 
00007 }
00008 
00009 float max6675::read_temp() {
00010     short value = 0;
00011     float temp = 0;
00012     
00013     uint8_t highByte=0;
00014     uint8_t lowByte=0;
00015     
00016     select();
00017     wait(.25); //This delay is needed else it does'nt seem to update the temp
00018 
00019     highByte = spi.write(0);
00020     lowByte = spi.write(0);
00021     deselect();
00022 
00023 
00024     if (lowByte & (1<<2)) {
00025         error("No Probe");
00026     } else {
00027         value = (highByte << 5 | lowByte>>3);
00028     }
00029 
00030     temp = (value*0.25); // Multiply the value by 0.25 to get temp in ˚C or
00031                          //  * (9.0/5.0)) + 32.0;   // Convert value to ˚F (ensure proper floats!)
00032 
00033 return temp;
00034 }
00035 
00036 void max6675::select() {
00037     ncs = 0;
00038 }
00039 
00040 void max6675::deselect() {
00041     ncs = 1;
00042 }