I am trying to connect a 5 volt serial GPS that I have to my router. My router has serial port on it that runs on 3.3 volts. I need to build a level shifter that can communicate to it. Heres the basic setup below.

I saw some directions on there internet for building a level shifter so the router can communicate to a computer but i believe that is 12volts. Here is the basic diagram.

I am a complete novice to all of this. Would it be hard to adjust the circuit above to 5v instead of 12v?

 

I'm pretty sure what you will want is a simple voltage divider using resistors...to get 5 to 3.3V

 

There is a long discussion of this on the piclist.com. Search the forum there. One method is using transistors, another is voltage divider, another is logic IC that have compatible in/out ......

 

If both ports are RS232 compatible you may route the signal direct. On the other hand if not. You may use a max232 type circuit as level translator. That is if one of the ports is of RS232 type and the other is not that kind. If both is not of RS232 type build your own level translator.