Arduino UNO + Arduino GSM Shield + Sparkfun Venus GPS

Question

I am using an Arduino UNO that is connected to an Arduino GSM shield (http://www.arduino.cc/en/Main/ArduinoGSMShield).

Now, I want to connect the SparkFun Venus GPS module to this combination. (*unfortunately due to my rep I can only post two links)

The Venus GPS works fine with the Arduino UNO by itself, but I am having some trouble getting the GPS module to communicate with the Arduino when the GSM shield is stacked on top.

The GPS powers on and begins blinking (which means it has a lock), but the serial monitor is not showing any information.

Coming from the programming side of things, I really don't understand much about electronics, so please pardon me if I am missing something basic here.

Based on what I've managed to figure out so far, I think it has something to do with the shield requiring 5V operating voltage and the Venus operating at 3.3V.

I think that when the GSM shield is plugged in, its expecting a 5V input, but the Venus GPS is only capable of sending a 3.3V signal. Furthermore, any other 5V sensors that I am currently using don't have any problems communicating with the UNO through the GSM shield.

So, I actually have two questions:

1. Is this assumption correct or could something else be the cause of my issue?
2. If this is correct, could I use something like this logic level converter (https://solarbotics.com/product/50550/) to step up the Venus GPS input signal?

Thank you in advance for any help and guidance you are able to provide.

Answer 1

I received my logic level converter today and wired it in between the Venus GPS and the Arduino GSM shield.

The issue seems to be resolved and I'm able to properly receive information from the TX on the Venus GPS. It would seem that my assumption was correct and I needed to "step-up" the 3.3V TX signal from the Venus GPS in order to use it with the GSM shield.