Parallax GPS Receiver Module #28146 I/O

fg

We are using your GPS module item no. 28146.

is any h/w is needed to interface the pin 3 "SIO" to 3.3v logic (e.g., Coridium wireless - www.coridiumcorp.com). In particular is a current limiting resistor required? Is that sufficient? What should it's value be and what if any other level shifting or other protection is needed?

Is there any danger if the connection doesn't revert to an input quick enough that damage could occur to the GSP module through pin 3?

Can you provide an equivalent circuit for pins 3 and 4?

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Chris Savage

This message is off topic and is being moved from the Completed Projects Forum to the Sensors Forum.

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Chris Savage
Parallax Engineering

Mike Green

When connecting the GPS module to a Propeller (with 3.3V logic), only a 1K to 2K series resistor is needed between SIO and a Propeller I/O pin. Presumably the same should work with other 3.3V logic I/O. There are other level shifters that can also be used between 3.3V and 5V logic. Some 3.3V microcontroller I/O pins are "5V tolerant" and are designed to be connected directly to 5V logic. Follow the microcontroller manufacturer's recommendations and use common sense. A 1K series resistor will protect the GPS module from accidental short circuits that can occur when the GPS module is trying to transmit data while the microcontroller I/O pin is also in output mode of the opposite state.

viskr

The LPC2103 on the Coridium wireless is 3.3V IO with 5V tolerant pins. They can be directly connected to the GPS module IOs without any resistor or level shifter.

Like all TTL if you are connecting directly to a 5V power supply you must use a limiting resistor.

The wireless board can be powered from a regulated 5V wall wart, which would then be able to supply power to the GPS module.