NO OUTPUT (VOLTAGE DROP) AT OUTPUT PIN

[katherina]

hi... i'm currently working on climbing robot, rite now, i've built the hardware and the circuit is done too.
however, there is no voltage drop at the output pin, n i wonder why is dat so?
because we have detected that the input pin is working, with 5v supply... but, it does not produce any output...  where could be the problem be?
 tq

[ed1380]

I'm not really getting you.

if there is no output there could be a lot of different problems. it was programmed wrong, soldered wrong, etc.

could you be more specific

[katherina]

i think the programming is correct....  there might be some electronics problem... but i dunno where the probkem could be...

[ed1380]

I'd take a multimeter and test the connections. also check that there are no shorts

[katherina]

soldering?
 i have check the crystal connection, etc... can't find where it is wrong.

usually, where could be the problem if there are no outputs at the pin of PIC 16F877A?

becoz there is input(voltage of 5V) at the input pin of the chip.

[katherina]

ok... tq, may i know which part to test? at the PIC???

[ed1380]

I'd start at the output pin that doesnt work

[paulstreats]

which pin is it? e.g rb1

[jsmoker]

yeah, you need to give a lot more information.  What kind of micro controller are you using?  When you say there's 5V at on the input pin, do you mean the Vcc/Vdd?  is your ground connected properly (Vss).  Some micro controllers are finicky about writing to the "latch" instead of the "port".   Are you sure that the "port" operation is primary.  Often times certain leads can double as a UART or SPI, etc so you have to make sure it's set to be a digital output first.  If you have a schematic of your circuit that you help greatly, too.  Even an MS Paint drawing would help.