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Author Topic: GPS wiring help  (Read 1007 times)

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Offline Aberg098Topic starter

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GPS wiring help
« on: August 03, 2010, 09:39:52 AM »
Hello all,

Although I admit to being a complete newbie at this, I need to tap into the wisdom of the SoR forums.

I'm interfacing an EM-408 GPS from sparkfun into an Axon2. Here's the datasheet I'm referring to:
http://www.usglobalsat.com/download/47/em408_ug.pdf

More specifically this part about the Rx pin (on page 5):

RX: This is the main receive channel for receiving software commands to the engine board from SiRfDemo software or from user-written software. (NOTE: When not in use this pin must be kept “HIGH” for operation. From Vcc connect a 470 Ohm resistor in series with a 3.2v Zener diode to Ground. Then, connect the Rx input to Zener’s cathode to pull the input “HIGH”.)

So I gather that I need a diode and a resistor. I think the correct diode to use is NTE 5005SM, since this is a 3.3V circuit. Where I'm not clear is what pin represents the anode and the cathode...


Offline Razor Concepts

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Re: GPS wiring help
« Reply #1 on: August 03, 2010, 10:20:03 AM »
The side with the stripe is the anode

Offline waltr

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Re: GPS wiring help
« Reply #2 on: August 03, 2010, 11:53:12 AM »
Quote
The side with the stripe is the anode

Did you try looking it up in Wiki?
http://en.wikipedia.org/wiki/Zener_diode

The stripe is the Cathode!

Offline Razor Concepts

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Re: GPS wiring help
« Reply #3 on: August 03, 2010, 11:58:41 AM »
Quote
The side with the stripe is the anode

Did you try looking it up in Wiki?
http://en.wikipedia.org/wiki/Zener_diode

The stripe is the Cathode!



DARN! Hope you didn't fry anything  :-X

Offline Aberg098Topic starter

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Re: GPS wiring help
« Reply #4 on: August 03, 2010, 01:07:57 PM »
Luckily I didn't fry anything, as I haven't received the diode yet!

That being said, somebody pointed out to me the following comment from the sparkfun product page:

by SteveMajor   +1.8 |   Feb 19, 2009 at  2:59pm   0
This device works beautifully. We hooked it up--indoors with no window for giggles--and it immediately got a 3d fix from 5 satellites with the on-board patch antenna alone. It should work even better outside. Some things not in the data sheet--tie both enable and RX to 3.3 V and the output is defaulted to 4800 baud 8,n,1. Our senior design group is very happy with this module. Another group is also having success with the EM-406A module.

So what should I do about this? try the diode thing, or just tie E/D to Rx to 3.3V? I really just need the gps to spit out data, nothing fancy.

 


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