Have I damaged my Javelin ?(Capacitors on serial port)

diafysal

I connected my Javelin exactly as on page 14 (curcuit A)(JavelinStampMan1-0.pdf).
Pin 4 VSS - only to pin 5 (in serial port)
And no capacitors.

Then I realized that it did not work without the serial cable connected to the computer.
Now after connecting it as in the errata pdf it works, but I wonder if I have damaged something?

How come the javelin does not work without the capacitor between pin 4 and pin 3?
Is VSS pin4 and VSS pin23 on the Javelin connected internally? (in the Javelin)

Post Edited (diafysal) : 7/20/2005 11:29:13 PM GMT

dandreae

The capacitor is used for decoupling so that the line can't be held high.· Yes, the pin4 and pin 23 are internally connected, a common ground through out.

Dave

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Dave Andreae

Tech Support
dandreae@parallax.com
Http://www.parallax.com

·

diafysal

The "decoupling capacitor" you are referring to is the one in between ATN - DTR I presume.

But what about the capacitor between ATN – VSS ?
My Javelin does not work without that in place.(after reset. Not connected to PC)

dandreae

You are correct, you· need both capacitors.· The second capacitor is used for a filter for noise and acts like a pull down.· If you look at the Javelin Demo board you'll notice it has both capacitors built on to the board.



Dave

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Dave Andreae

Tech Support
dandreae@parallax.com
Http://www.parallax.com

·

diafysal

So the small leak current in the capacitor pulls down the ATN to a logical zero?
And without the capacitor the Javelin can get stuck in a "programming mode"?

And I presume I did not damage the Javelin.

Beau Schwabe

diafysal,

You said...
So the small leak current in the capacitor pulls down the ATN to a logical zero?

Not exactly,· inside the BS2 module (http://www.parallax.com/dl/docs/prod/schem/BS2RevF.pdf) the
equivalent of 10K is in parallel with the capacitor across pins 3 & 4 with the dual 2n3904/resistor
arrangement on the BS2.· The effect of·the capacitor in parallel with the resistor makes this circuit
look·like a "fast-blow" fuse capable of resetting itself.
·
·


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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

diafysal

So .... It is normal that the Javelin does not work without that capacitor.
And I did not damage the Javelin ? (without the capacitor)

Thank you for the replies.

Post Edited (diafysal) : 7/22/2005 10:57:00 PM GMT

Silo89

Hello,

I am new to this forum. And not to long ago I adquired a Javelin stamp. I have read the manual and re-typed the sample code for the firts exercise "ButtonLed",
and finally I ran into this post on this forum.
I have the Javelin, and I am confuse about these two capicitors. I am aware about the two capacitor on the Javelin demo and I have ran continuity test from this capacitors to the serial pins 4 and 5, and to the the ATN and VSS and they appeared to be connected.

Now, is there anything else I need to solder, attach or wire in order for the javelin to work. The update to the manual, which adds the capacitors in the diagram, is that something we physically have to do, or is it just to be correct.

I have the correct power supplied, I ordered from Parallax.
I am able to connect and download the programs, but they will not execute.
I am aware of the the new wiring update to this diagram.


Please advise, I'll be honest I am confuse.

Thank You

Chris Savage

Silo,

·· Please start a new thread for this question, as it is unrelated to the current thread.

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Chris Savage
Parallax Tech Support
csavage@parallax.com