Parallax GPS Module single wire interface


Is there a way to connect both the RX and TX pin to a Serial io pin of the Parallax GPS module?

I know it is possible to just receive the RAW data and parse for the wanted information (longitude and latitude). But I would like to be able to just request part of the data whenever it is needed.

Would be great if someone could give me a hint. Maybe it is possible to detach rx while tx is sending and the other way around.

cheers, Stephan.

Why don't you use the software serial library?

Hello bigengineer

The GPS modul has only one pin to send and receive data. It seems that the serial library has rx to receive and tx to send data. I need one pin or one wire that does both.

Can i do that with the serial libarary?


I have a GPS unit only connected to receive data. Filtering of specific parts of the string is done in software. Looking for this example I also found this

Yeah that is what I am doing right now but I was hoping to learn how to establish a two way communication.

Thanks anyway for you response.



if you haven't already bought the Parallax module, then you can get a single unit gps module for the same price or less. Polstar (they make the GPS receiver on the Parallax) makes something called the GPS mouse, which has bidirectional serial and an integrated antenna. Garmin and a lot of other people make these too. They all work on standard RS-232 connections, and give out NMEA standard data. Standard GPS units liek the Garmin GPS-12XL will also receive commands and give out NMEA in response.

As people have said above though, it makes sense to just parse it in software.. is there a particular string you are looking for?


Hey Daniel.

I only need the longitude. I managed to parse the RAW data for just the longitude. But I wanted to see if it is faster to use the two way communication and only request the one string I need.

Since timing is an issue for my project (creating drum rhythms) I am searching for the fastest solution.

cheers, stephan.


you should check the update rate for the GPS engine used int he Parallax unit. Most modules are about once per second, although lately I have seen others that are faster. It takes time to triangulate :)