Graynomad:
So analogRead(15) will only work if the TSON bit in ADC_ACR is set by the looks of it. So it's up to the Arduino guys to do that or I guess you can do it yourself.
Rob
in hardware/arduino/sam/system/libsam/source/adc.c there is an adc_enable_ts() that sets ADC_ACR_TSON, and the temperature calculation is described in Chapter 46.8 of reference pdf, 2.65mv/deg and 0.8v at 27C