Help with wiring piface to an L298 h bridge

I have a Pi-Face which I have successfully used to switch on and off some LED's but I'm a bit stuck on taking the next step - to drive a robot chassis.

I purchased one of these l298 motor drivers but I'm completely stuck on how to connect up the pi faces open collector outputs to the l298.

From searching about on the net it appears that it definitely possible but I just cant figure it out.

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johnbeetem over 13 years ago

Open collector outputs can only pull down to ground, so I suspect you need a pull-up resistor (say, 4.7K Ohm) to 3.3V or to 5V for each signal that connects to an L298 logic input. According to my ST L298 data sheet, it expects TTL-level inputs and anything over 2.3 V is considered logic high.
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e14 Contributor over 13 years ago in reply to johnbeetem

I did try putting together a pull up resitor but I was obviously wireing it wrong. I became a little confused as to where the open collector was wired in. Do you have an example diagram or something that shows how to make the circuit?
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Problemchild over 13 years ago in reply to e14 Contributor

The resistor goes between the output of the ULN22803 and 5V .
I would also take a min to actually measure the voltage at the out put before you start to see if your program is actually changeing the voltageon the pin you expect!
Easy done
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Problemchild over 13 years ago in reply to e14 Contributor

The resistor goes between the output of the ULN22803 and 5V .
I would also take a min to actually measure the voltage at the out put before you start to see if your program is actually changeing the voltageon the pin you expect!
Easy done
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