​​

Voltage input to an IO port

Problem:

How to set up the I/O ports to accept a voltage input.

Resolution:

The I/O ports have a voltage present in idle mode, which is used to detect a short in the input.

In order to use a voltage input, the voltage must be lowered to allow the input voltage to be detected.

To do this, use a 2,000 ohm resistor across the desired I/O to shunt the bias voltage to ground.

Wire the input circuit across the resistor to raise the voltage on the I/O back to a level above 5 VDC.

Maximum input voltage is +12 VDC.

Use the following diagram for reference.​

​