Newbie DemoBoard Question

jhoyoza

I have been reading, and reading, reading.....and slowley I think it is starting to sink in.

I finally got around to trying exercise 1: as laid out in the Prop manual.

PUB Toggle
dira[noparse][[/noparse]16]~~
repeat
!outa[noparse][[/noparse]16]
waitcnt (3_000_000 + cnt)

And yes the LED on the board flashed as described. I changed the pin number to 17 and it still works AOK.

However, as I changed the pin number to 18 and above the proper LED lights up but the one directly adjacent also lights. Not as bright but still lights up.

For instance:

PUB Toggle
dira[noparse][[/noparse]18]~~
repeat
!outa[noparse][[/noparse]18]
waitcnt (3_000_000 + cnt)

LED 18 lights up Ok but 19 lights up also at about half the brightness.

PUB Toggle
dira[noparse][[/noparse]19]~~
repeat
!outa[noparse][[/noparse]19]
waitcnt (3_000_000 + cnt)

LEd 19 lights up but 18 also lights up at about half the intensity.

This is true as I change all the way up to pin 23? The adjacent LED also lights up.

Could it be possible there is some leakage or perhaps I have a defective Demo-Board? Or is it something I'm doing or not doing?

Thanks!

-J

P.S. For photo purposes I set time to (1_000 +cnt) but it still does it at (3_000_000+cnt)

Post Edited (jhoyoza) : 4/26/2007 12:07:22 PM GMT

Kaio

That is a normally behavior on a Demo board. Please have a look at the schematic PDF of your board.

The pins 18 and 19, 20 and 21 and also 22 and 23 are wired as a digital-analog converter using resistors for the RGB of VGA output. Therefore when you switch on one of this pins this will also drive the LED on the wired pin via the resistors.

jhoyoza

Whew!

Of course, I didn't bother to look at the schematic and I thank you for pointing it out. (Dolt!)

Yes, I can see those pins are tied through the VGA R1 through R6 resistors in pairs. Pins p16 and 17 are not paired.

Thank you! And for your patience and consideration dealing with a lowly Newbie.

-J

Kaio

No problem, I'm glad to help you. We were all newbie before a few month.

parts-man73

I remember someone once saying that you can prevent the other LED in the pair from lighting if you drive that output low. I don't have a demoboard to verify that, could someone else chime in if this is correct (or incorrect)?? I did a quick search and couldn't find the thread that mentioned that.

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Brian Meade

"They who dream by day are cognizant of many things which escape those who dream only by night" - Edgar Poe

Paul Baker

parts-man73 said...
I remember someone once saying that you can prevent the other LED in the pair from lighting if you drive that output low. I don't have a demoboard to verify that, could someone else chime in if this is correct (or incorrect)?? I did a quick search and couldn't find the thread that mentioned that.

It's true, active driving the adjacent LED will make the co-lighting go away.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

jhoyoza

Well watta' yah know!

Brian Meade said...
I remember someone once saying that you can prevent the other LED in the pair from lighting if you drive that output low.

Paul Baker said...
It's true, active driving the adjacent LED will make the co-lighting go away.

{{ Output.spin }}

PUB Toggle
  dira[noparse][[/noparse]18..19]~~  'Make pin 19 an output seems to do it          
  repeat
     !outa[noparse][[/noparse]18] 
     waitcnt(3_000_000 + cnt)

You just have to love this place.

Thank you!

Post Edited (jhoyoza) : 4/26/2007 8:12:01 PM GMT