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Driving problem with PCF8575

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alzomor

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When I connect the PCF8575 outputs to the optocoupler through a 390 ohm resistor and drive the output high the output of the PCF8575 is 1V.

Vf of the input led of the MOC3606 optocoupler is 1.2V , so the current sinked from the port is (5V-1.2)/390=9.74mA

May you kindly tell me what is wrong with my calculations and design and how to solve the problem
Attached you can find schematic for my circuit

Regards
Hossam Alzomor
 

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