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Problem in driving low output on port

 
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akshaymathur39



Joined: 05 Aug 2008
Posts: 11

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Problem in driving low output on port
PostPosted: Fri Apr 23, 2010 8:50 pm     Reply with quote

Hi,

I am facing some issues in driving output to low using output_low(PIN_A2).

Here are the readings:
1) output_low(PIN_A2) : 0.71V
2) output_high(PIN_A2): 3.3V

Kindly let me know what can be the issue. This problem occuring on PORTA and PORTC but not on PORTG. I am using PIC18F67J50.

Please let me know what can be reason. I am not using fast_io.

Thanks
SherpaDoug



Joined: 07 Sep 2003
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Location: Cape Cod Mass USA

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PostPosted: Fri Apr 23, 2010 9:26 pm     Reply with quote

Those seem like valid logic low and high voltage levels. How much current are you putting through the pin? What is your supply voltage? What does the data sheet say you should be expecting?
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akshaymathur39



Joined: 05 Aug 2008
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PostPosted: Sat Apr 24, 2010 10:10 pm     Reply with quote

Maximum Low Voltage: 0.4V
Minimum High Voltage: 2.4V specified at Vdd = 3.3V

My supply voltage is 3.3V and I am just using multimeter to check voltage, there is no load driven through the pin.
vinniewryan



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PostPosted: Sun Apr 25, 2010 1:23 am     Reply with quote

Are you using a pull-down resistor? If you want a lower 'low', connect a resistor from the pin to ground. I use 100K pulldown resistors for most of the output pins I use, and 2.2-10K for inputs that need a good ground reference. It really depends on your circuits needs.
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