At 09:17 AM 5/19/2006 -0700, you wrote:
>Hi,
>
>I have a 18F452 in a home made board. This pic has the main responsibility 
>of generating PWM signals to control RC servos.
>A while ago I was doing some tests with AND gates, but not directly 
>related to the pic. Then I removed the AND gate, and now the PWM signal is 
>wicked.
>The timing is correct (1ms pulse on a 20ms pulsetrain), but the amplitude 
>is wrong. Before I had 0-5V, and now I'm getting 0-1V. I tried both with 
>the servo connected to it and with nothing connected to the port.
>
>I didn't measure the other outputs (LEDs), but since they are as bright as 
>before, I assumed they are ok. Is it possible to damage only one (in this 
>case two) ports? Any other suggestions?

If you're looking at it on a 20MHz  or better oscilloscope and the signal
is going cleanly from 0V to ~1V with nothing connected to it, then you've
hosed the output.

If you're reading the average voltage on a DVM, it could be just about
anything. If you don't have any better tools and the chip is soldered in,
reprogram it to set the port high and read the voltages. If you've got a
socket, swap chips with a known-good chip.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->>Test equipment, parts OLED displys http://search.ebay.com/_W0QQsassZspeff


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