Low-Cost Temperature Measurement with a Microcontroller

It frequently happens that you have an application in which you want to measure the temperature of a circuit or the outside world. This can be easily achieved using additional components in the form of ICs, or by using a RC network and a software routine. However, if all the I/O port pins are already in use, it’s hard to know what to do. A circuit trick can provide a solution to this dilemma.As a rule, modern microcontrollers have RC oscillators with (relatively large) temperature coefficients. Since instructions are processed at the speed of the RC clock, the execution time of a software loop varies with the chip temperature.