basic stamp and telit module

martijn

Hi i'm a beginner to electronics. I now did several projects using the basic stamp 2.
I just received the Telit GM 862 - gps module.

The first thing i like to do is just use the modem and send AT commands from the pc or the basic stamp (RS232) to the telit module. Therefor i need to connect the RX and TX.
The problem is that a direct connection is not possible, i need a level translator. I don't know how this exactly works or what i need.

The manual says:
In order to interface the Telit GM862-GPS with a PC com port or a RS232 (EIA/TIA-232) application a
level translator is required. This level translator must
• invert the electrical signal in both directions
• change the level from 0/3V to +15/-15V
....

http://www.telit.com/module/infopool/download.php?id=871

can someone tell me how i connect the parts and what parts i need?
I appreciate for helping out a beginner!

Mike Green

The type of device you need is a MAX3232 or equivalent. They are made by a large number of manufacturers including Maxim (www.maxim-ic.com/quick_view2.cfm/qv_pk/1068). Download their datasheet and application notes. A websearch for MAX232 or MAX3232 should also turn up a lot of articles on its use.

This Telit module is a low voltage logic module (2.8V to 3.3V max.) and can be destroyed by connecting it directly to a Stamp. The MAX3232 is a low voltage (3.0-3.3V) version of the MAX232 which is a 5V device. Using a MAX232 can also destroy the Telit module.

There's a long "sticky" thread at the top of the list for the Propeller forum that deals with connecting 3.3V and 5V logic together since the Propeller is a 3.3V logic device and often has to be connected to 5V logic devices. Have a look there. All of that applies to connecting a Stamp to a 3.3V or 3.0V device, just with roles reversed.

Post Edited (Mike Green) : 5/15/2008 4:02:43 PM GMT

martijn

Hi Mike, i really appreciate your help!

Before i messed up the Telit module i draw a quick scheme in Photopshop, because i dont have a program for drawing schemes.. Although, i hope i'm getting there but nevertheless the scheme is not yet done.

In the Telit manual it says indeed i need to use a Max3237!

Can you take a look at the scheme and tell me if i'am in the good direction?

Tanks in advance!

FireHopper

It was suggested to me to use tinycad for doing schema. [noparse]:)[/noparse] search for it using google [noparse]:)[/noparse] issa free. and it works good. (thanks whit)