Set Arduino pin to High Impedance (floating)

Discussion in 'The Projects Forum' started by sirch2, Jan 28, 2013.

  1. sirch2

    sirch2 Thread Starter Active Member

    Jan 21, 2013
    The circuit shown below is for a 40kHz ultrasonic rangefinder. I have put together a variation of the circuit using an Arduino and not including the I2C code/connector (the original code is in Assembly with which I am not too familiar so I am rewriting it).

    The reciever section includes 4 Op Amps, the middle two of which are supposed to provide selectable gain. I am assuming that I need to toggle the resistsors from High Impedance to Low (ground) to change the gain and I can set the relevat pins to OUTPUT, LOW to ground them.

    My question is how do I set the pins back to floating in on the Arduino? Would it be enough to set it to HIGH?

  2. MrChips

    MrChips Moderator

    Oct 2, 2009
    There is a register called DDRA. Set this to 0 to set all pins of PORTA to high impedance.
    Specifically, set the corresponding bit to 1 that you wish to be an output.