Measure voltage polarity with io pin?

Botdocter

I have been searching through the prop manual, but wasn't able to find anything.

I need to measure the polarity of 5v. So one moment it will be +5V an then the next -5V. nothing in between just like a switch on and of.

i use the robot control board.

any help is welcome!

ErNa

This is quite simple to do: connect an input to the voltage via 100k. Low input will show low voltage input, a negative voltage will be clamped by the input protection diode (internal), high shows a positive voltage > 1.2V

Botdocter

Oops, i forgot to mention that there are accually three states. Disconnected, -5v, +5v.
It is a weird decoder from a rc car that is used for sensing wheel direction.

Disconnected is in the straight forward, -5v is left and +5v is right.

Ariba

Something like that:

Botdocter

indeed! i just thought of the same diagram only with diodes. so can you point me to a example for the spin code?

StefanL38

hm - to be honest:

I was asking myself "did botdocter code only a few codelines by himself?"
My answer ist YES! for sure! But why is he asking then? I think it is quite simple

pseudo-code

if (ina[pin1] == 1) and (ina[pin2] == 0)
open - no voltage

if (ina[pin1] == 1) and (ina[pin2] == 1)
+5V

if (ina[pin1] == 0) and (ina[pin2] == 0)
-5V
best regards

Stefan

Botdocter

Thank you. This is very clear.

I don't know exactly what you mean with this though:

hm - to be honest:

I was asking myself "did botdocter code only a few codelines by himself?"
My answer ist YES! for sure! But why is he asking then? I think it is quite simple

MagIO2

This is called sarcasm.