Interfacing with the 50-pins on GM-862

Hello everybody!

I have recently bought an GM862-GPS module from SparkFun with two boards:

Basic 50pin Eval Board:

Eval Board USB:

I have successfully connected the Eval Board USB to my computer with only the USB cable connected and made both .NET and HyperTerminal speak to the modem.

However, my goal is to make the Arduino board speak with the GM862 with the basic 50-pin board, but i cannot get it working. I'm quite new at electronics so I don't read schematics very well (by the way, if any of you got a link to a nice tutorial please post).

I do not know how to make the Arduino talk to the GM862 but have tried several examples on the net fx:

(This is though not the basic 50-pin). What I have done is:

Connecting pin 7 (5V) and GND from Arduino to the GM-862 pin 3.8V and GND. I have tried to connect TX-I from GM-862 to TX (pin 1) on Arduino and RX-0 on GM-862 to RX (pin 0) on Arduino without any results. I have also tried to put the STAT_LED and PWRMON to a positive end of a LED and then the negative end of the LED to ground, also without any results.

Hope you can help me out. I've got Arduino Duemilanove btw.

Sorry for my bad english. I think I've done some things very wrong, but I'm a newbie in this electronics area.

Thanks in advance :)


Hi, I've just spent a couple of weeks trying to sort this out myself so hopefully can help point you in the right direction.

If you go back to the sparkfun site and look at the schematic for the rs232 version of the GM862 evaluation board here:-

It gives you details for how to connect status led and power monitor led and on page 2 you will see a level translation circuit for RS232 using a maxim3232 IC. I used this setup to connect an RS232 arduino to the GM862.

Read all the info you can find on logic level translation - it's important.

If you decide to use the same setup as on the schematic you will probably have to perform some translation at the arduino. For this you could use the maxim232 IC. Datasheets show how to connect these up - it's fairly straightforward - 4 caps only.

As you are using the usb version hopefully someone will offer some alternative but failing that if you follow this it should work.

To connect the arduino and gm862 use three wires - Rx, Tx and Ground only.

I'm no expert on these things but if I can help in any way please let me know.



I've just finished a post about interfacing a GM862 with an Arduino Mega. Maybe it's helpful to you.

Cheers, Alex