I have it sending data now. I had to chenge retval to max_retval in the print statement
/*********************************************************************************
** MAX31855 Cold-Junction Compensated Thermocouple-to-Digital Converter
*********************************************************************************/
case 0xFD: // Init
MAX31855_Init(command[2], command[3], command[4]);
Serial.write('0');
break;
case 0xFE: // Read Raw Data
// Read raw data here.
max_retVal = MAX31855_readData();
Serial.write( (max_retVal >> 24) );
Serial.write( (max_retVal >> 16 & 0xFF) );
Serial.write( (max_retVal >> 8 & 0xFF) );
Serial.write( (max_retVal & 0xFF) );
break;
Also it reads on the hi to low transition so I fixed that in the code as well.
// MAX31855 Functions
void MAX31855_Init(unsigned char SO, unsigned char CS, unsigned char SCK)
{
max_so = SO;
max_cs = CS;
max_sck = SCK;
// MAX31855 data output pin
pinMode(max_so, INPUT);
// MAX31855 chip select input pin
pinMode(max_cs, OUTPUT);
// MAX31855 clock input pin
pinMode(max_sck, OUTPUT);
// Default output pins state
digitalWrite(max_cs, HIGH);
digitalWrite(max_sck, HIGH);
}
unsigned long MAX31855_readData()
{
int bitCount;
unsigned long data;
// Clear data
data = 0;
// Select the MAX31855 chip
digitalWrite(max_cs, LOW);
// Shift in 32-bit of data
for (bitCount = 31; bitCount >= 0; bitCount--)
{
digitalWrite(max_sck, LOW);
// If data bit is high
if (digitalRead(max_so))
{
// Need to type cast data type to unsigned long, else compiler will
// truncate to 16-bit
data |= ((unsigned long)1 << bitCount);
}
digitalWrite(max_sck, HIGH);
}
// Deselect MAX31855 chip
digitalWrite(max_cs, HIGH);
return(data);
}
