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Dependents: max31855Sample Reflow_Oven_Controller test_draft Soldering_Tips_Thermometer
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Interface library for the MAX31855 Cold Junction Compendated Thermocouple-to-Digital Converter. This part is the reaplacement for the now discontinued MAX6675. The library is based on the original MAX6675 library found on this site altered to fit the serial specification of the new chip as well as adding a few new features.
The main new feature of note is that the library itself deals with the 0.25 second delay required to complete a conversion. Polling the 'ready()' function will return a '1' when the chip is read to submit a new reading.
#include "mbed.h"
#include "max31855.h"
DigitalOut myled(LED1);
//----------------------------------------------------------
//SPI Interfaces
SPI testSPI(p11,p12,p13);
//----------------------------------------------------------
//----------------------------------------------------------
//Thermocouples
max31855 max1(testSPI,p21);
//----------------------------------------------------------
int main() {
//Initialise chip (starts internal timer)
max1.initialise();
//Float value to hold temperature returned
float fvalue = 0;
while(1) {
//Check if the chip is ready for a reading to be taken
if (max1.ready()==1){
//Get the reading
fvalue = max1.read_temp();
if (fvalue > 2000){
if(fvalue==2001){
printf("No TC");
}else if(fvalue==2002){
printf("Short to Ground");
}else if(fvalue==2004){
printf("Short to VCC");
}
}else{
printf("Temperature is: %f\n\r", fvalue);
}
}
//Heartbeat signal (not necessary)
myled = !myled;
//Delay is not required, here simply for test program
wait(0.25);
}
}