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Unread 27-01-2015, 09:17
crake crake is offline
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Re: Photoeye's not working-Difference between RoboRIO and Digital Side Card?

Forgive me, I was channeling my physics professor there for a moment. He never told me the answer directly (team 900, am I right?)

There are a couple of differences between myRIO and cRIO.

myRIO DIO (for the most part - there are exceptions with DIO14 and DIO15 which are 2.2k to 3.3V) have 40k pull up to 3.3V

cRIO DIO with side car has a 10k pull up to 5V AND a weak >20k pull DOWN (internal to an ASIC on the NI 9403 module).

This means that the roboRIO has a far weaker pull up than the cRIO w/side car.

From the datasheets it isn't entirely clear to me how they have NPN circuit configured, but I suspect that if you had a strong pull up your sensor will start working. I agree that the differences in saturation voltages is a strong candidate as to why some sensors work with roboRIO as-configured while others don't.

Anyway, try placing a nice strong pull-up on DIO to 3.3V (say, 1k).