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Author Topic: Interfacing 3.3v GPS with 5v Freeduino  (Read 749 times)
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Hello!
I've just assembled Freeduino board and it works perfectly.

I have usb GPS which I want to use with my arduino.
The chip inside the receiver has only 4 wires - +/GND/RX/TX which is very convenient. Unfortunately I don't know the name of the chip. What I do know that it uses 3.3.v.
I can't connect it to the board as it draws more than 40ma.

So I think I'm going to use LD1117 for power, but what about serial lines?
Do I have to use something? If so, examples would be very appreciated.

Thank you in advance!
Leonti
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Same thing you need to do with xbee,s .
you need to use a voltage divider from 2 resistors for the Rx on the gps , but you don`t have to do anything about the tx from the gps , 3.3v is still o.k
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This would work nicely to convert 2 signal lines to and from 3.3-5.0 volts.

http://www.sparkfun.com/commerce/product_info.php?products_id=8745

Lefty
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Thank you for replies!
peter247, how this divider would look like? What would be the resistors values?
Lefty, I'm writing from Poland, so it would take to long to get that converter and too expensive (shipping).

Leonti
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I just used 2 equal vaule resistors (4.7k)

                     :
(gnd) resistor (rx) resistor ( 0 )
                                      :
                                      :
                                   ( tx )

Which converts the 5v to 2.5v which worked with the xbees

But if you wanted 3.3v just mess with the ratio of the resistors to get 3.3v at rx
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the sparkfun device is just a couple mosfetts and resistors which you could build as well if you have access to the parts
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The Arduino work with 3.3 volt so there is no point in using a mosfet to level up.

The level down part is just like my I did , but with 10k resistors.

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