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Fork of MAX31855 by
max31855.cpp
- Committer:
- Stavlin
- Date:
- 2012-08-16
- Revision:
- 0:656c522152d4
- Child:
- 1:5eeee89cb281
File content as of revision 0:656c522152d4:
#include <mbed.h> #include "max31855.h" max31855::max31855(SPI& _spi, PinName _ncs) : spi(_spi), ncs(_ncs) { } float max31855::read_temp() { short value = 0; float temp = 0; //Variables to hold probe temperature uint8_t tempProbeHigh=0; uint8_t tempProbeLow=0; //Variables to hold chip temperature and device status uint8_t tempChipHigh=0; uint8_t tempChipLow=0; if (pollTimer.read_ms() > 250){ //Set CS to initiate transfer and stop conversion select(); //Read in Probe tempeature tempProbeHigh = spi.write(0); tempProbeLow = spi.write(0); //Get the chip temperature and the fault data tempChipHigh = spi.write(0); tempChipLow = spi.write(0); //Set the chip temperature chipTemp = (tempChipHigh<<4 | tempChipLow>>4)*0.25; //Check for a fault (last bit of transfer is fault bit) if ((tempProbeLow & 1)==1){ //Chip reports a fault, extract fault from Chip Temperature data int faultType = (tempChipLow & 7); if (faultType==1){ //Open circuit (no TC) return 0.1; }else if (faultType==2){ //Short to GND return 0.2; }else if (faultType==4){ //Short to VCC return 0.4; }else{ return 0.5; } }else{ //Set CS to stop transfer and restart conversion deselect(); //Integer value of temperature value = (tempProbeHigh<< 6 | tempProbeLow>>2); //Get actual temperature (last 2 bits of integer are decimal 0.5 and 0.25) temp = (value*0.25); // Multiply the value by 0.25 to get temp in C or // * (9.0/5.0)) + 32.0; // Convert value to F (ensure proper floats!) return temp; } }else{ //Chip not ready for reading return -1; } } void max31855::select() { //Set CS low to start transmission (interrupts conversion) ncs = 0; } void max31855::deselect() { //Set CS high to stop transmission (restarts conversion) ncs = 1; //Reset conversion timer pollTimer.reset(); } void max31855::initialise() { //Start the conversion timer pollTimer.start(); } int max31855::ready() { //Check to see if conversion is complete if (pollTimer.read_ms() > 250) { //Conversion complete return 1; }else{ //Conversion incomplete return 0; } }