I am interfacing with an existing product. This product uses a PIC16F54 uC and is ultimately driving a solenoid. This device is a black box to me and I have no input into the software running on the device or the design of it. I have identified the pins on the UC which receive the input and control the output of the solenoid.
Without going into all the specifics, my device is going to "piggy back" onto the existing device and give an alternative method of control to the device while reading its output and input.
my uC will need to be able read the same inputs and also control the output. I don't imagine connecting the inputs together so both uCs can see the input will be a problem. However, the outputs will be a problem. One might be driving the pin low, while another is driving the pin high.
What are my options to overcome this? Ideally, I'd like to tap just two or three points and not get into cutting traces to add additional circuitry.
I am thinking my best bet might just be a "man-in-the-middle" type scenario where I cut the output trace from the device uC and wire that as an input into my uC and then make my uC control the output itself.
My uC will be a rasberry PI w/ TE291 3V/5V shifters to get me to the 5V the PIC is using.