Mega to DUE voltage problem

Using Arduino IDE 1.x
1

Hi Everyone,

I Have upgraded my Mega to a DUE as I needed a faster MCU for some graphics stuff I will be using later on in my project and have run into a problem I don't completely understand from DUE side. The project worked fine with the MEGA. Code works on both and everything else works except two optocouplers that will not turn on with the DUE.

The only thing I can figure is the voltage on digital pins (when high) is only 0.922v where the mega is 1.2v. I have a 1k resistor between the pin and the opto. Voltage between the resistor and opt is 1.010v mega and ~ 0.880v due.

Opto is a 817a

Is there any way I can up the output voltage on the digital pin?

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3

Thanks for your help. I've tried this and it does not work, I am getting .920v with the parallel resistors which is pretty much max what the pin produces. Looks like I need at least 1 volt for the opt to trigger.

4

The output voltage on a DUE digital pin should be close to 3.3V or 0V, certainly not 0.9V !!

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