I developed a circuit to read a thermocouple using a microcontroller without the insanely expensive and difficult to obtain MAX6675.
Turns out the TI TMP513 Power Supply Monitor chip is ideal for reading a thermocouple. It’s got a built-in temperature sensor for cold junction compensation and the ADC designed for measuring voltage in a shunt resistor is 12 bits with a full scale range of 40 mV. It uses an I2C interface.
I used the TMP513 with a PIC18F-series microcontroller and Swordfish Basic. The thermocouple circuit was quickly built on an SOIC-DIP adapter circuit board. I use a lookup table and interpolation for the best possible accuracy. I used a type K thermocouple but a table for any desired type can easily be used. The results are excellent.
A Thermocouple Measurement Circuit with Swordfish Software – [Link]