Identify Micro Controller High Impedance input

[ranaya]

Hi every1...

How can we identify whether a micro controller input pin is occupied or not using programming code? . Means when an analog or a digital input pin is not connected to anything (high impedance state) is there a way to identify it ? (say pic mcu)

Thanx

 

[D.A.(Tony)Stewart]

THey do this all the time in ATE design ( for at least 50yrs) It is call back driving test pin and sense voltage. It must be an analog port for accuracy otherwise you need to be clever... e.g. drive low then floating = input then measure & repeat... notice if pull up, pull down or drift due to RC load. measure time constant then time out. THis is done all the time in Analog audio ports for PC with drivers.