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[PIC] PIC16F877A produces an output voltage of only2.5 to 3 v not 5v when progrmed to high

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7ezhil7

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I have programed my PIC16f877a to yield HIGH(logic 1) in all of the pins.But on execution it yields only utmost 3v.I tried programing in both Mplab IDE and Mikro C.It results same.Is there any mistake with my setting? As my Dev board contains 10MHz crystal I have selected HS oscillator.I use PICKIT2 v2.61 programmer.Please help me.
 

Hi

I think it's not software problem.

1. Check your VCC & GND voltage?
2. Check your crystal output with oscilloscope?
3. Check MCLR pin for high.
 

All the supply were good vcc=4.98
mclr=4.98
gnd=0
 

What about 2?

- - - Updated - - -

If you do not have oscilloscope... change new crystal & check capacitors value also according to crystal.
 

Hi,

.Is there any mistake with my setting?
Click to expand...
We don't know, because we don't see your setting...

Why not 5V..
* are the pins absolutely unconnected?
* is the watchdog switched off?
* do you have an infinite main loop....doing nothing?
* are any interrupts enabled?

Klaus
 

Is it only one pin?
The reason could be
program not work, and you have tri state outputs,
pin not set to be output - how about TRIS?
pin source too much current,
pin oscilate and you measure DC.


solutions:
show us your soft,
measure pin state with AC - while oscilating there will be voltage on AC,
measure voltage with resistor (~kohm) conected to ground. if pin is really output, the voltage sholuld be ~the same

how about low level voltage?
try to write soft with loop 1 s low, 1 s high, it is something you are able to measure without oscilloscope
 

share your code with us, so that real solution can be given. And whihc dev board it is? Do check various configuaration settings like PWM, Timer1 OSCEN, OSC switch etc... Wrong setting of this bits can create various problems.
 

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