18F2550 timing

[Bruce]

How do you know it pauses just for 258ms?

If you are not sure PAUSE 1 works, then setup a simple loop to toggle a pin, and watch
it with a scope.

[sstt1976]

I know those pauses are what they are because the circuit outputs a MIDI note across USB to a host computer and an app on that host measures the time between events. Both examples should theoretically pause 2000ms between each MIDI note indicator .

I'll try the pin toggle to the scope idea. Seems like Pause 1 will take just .129ms because 2000 times through the loop is taking only 258ms for some reason.

[Bruce]

I think you may be forgetting to add the time it takes for certain functions to execute.

PAUSE 2000 pauses for 2000 * 1mS.

For cnt=1 to 2000 ' this takes time
Usbservice ' this takes time
Pause 1 ' this should take about 1mS
Next cnt ' this takes time

Obviously, the 2nd version is NOT the same. You have to account for the time Usbservice
takes + the time to execute the for next loop.

[sstt1976]

What you said could make sense if the 2nd version actually was taking longer, but it's running 8 times faster.

remember, pause 2000 is measuring out as 2000ms but the loop example is completing in 258ms!

[Bruce]

I'm totally guessing here, but it sounds like you might have declared your cnt variable as
a byte VS a word.

[sstt1976]

You got it. Thanks very much!

Now my question is, in the 1st example, how is my USB staying connected all the while during the 'Pause 2000' statement? I though 'Usbservice' needed to be thrown in there almost constantly?

[Bruce]

how is my USB staying connected all the while during the 'Pause 2000'

I think you'll find this varies from one PC to the next. Yes, I have tested it, and yes it does
vary. Why? Your guess is as good as mine...;o}

It may also have something to do with the host software, hub or no hub, number of active
USB devices online, your butt angle in your seat, position of the stars, etc, etc, but I have
seen a HUGE difference in time requirements from one app to the next.

I have a 1-wire temp logger that waits well over 1 second that's never failed. Go figure!