@M7460 there is a built-in 27K resistor between the IN pin and the +3.3V pin on all the IO ports. However, to read a standard 100K thermistor you should use an additional lower value resistor connected externally between those two pins. I suggest a value of either 4.7K or 3.3K. Then in the M308 command for that temperature sensor you will need to use the R parameter to tell RRF the effective resistance between the IN pin and +3.3V, which will be the parallel combination of your external resistor and the 27K internal resistor.