Connecting Arduino to GM862 breakout board problem

I ordered the GM862 and RS232 sparkfun breakout board ( and got the module working connected to my serial port on my laptop. However, I am having problems getting a serial connection from the Arduino to the breakout board. I tried connecting the TX and RX pins of the Arduino to the TXD RXD RX-0 TX-1 and even to the DB9 female connector on the breakout board, with and without ground, reversed the TX, RX, and even tried pulling out the Atmega328 from my Arduino and connecting in terminal using all the methods and typing AT but not getting any response like I should.

I am pretty new to electronics but never had a problem like this connecting the Arduino to a part via TX and RX. Since I reversed the lines (which could damage things), I double checked that the module and everything still works and its still working fine on my computer.

Hope someone can help, been playing with this for a few hours now.

Update - I can use just the TX and GND from my laptops serial port to send a command to the gprs module, i disconnected everything else and it works fine. I tried to do the same with the Arduino by connecting the TX and the GND from the arduino to the serial breakout board but nothing.

Hi, You can connect the Arduino RXD ant TXD with the Sparfun board but I think that there is needed to disconnect TX and RX from MAX3232 first using the solder jumpers on the evaluation board. In case you will need to communicate with GSM Module from PC again, you need to solder it back. Or you can add some jumpers like I see it was on the previous board version. Furthemore you need to change the voltage levels from 5V to 2,8V to be able to communicate with the GSM Module. You can just do it using resistor divider for 5 to 2,8V and connect directly for 2,8V to 5V.... There is an example how to do it Good luck! :) BR, Oldrich

Hi all,

I have purchased the GM862 USB evaluation board from Sparkfun. I have successfully got it to work with the PC's hyperterminal, i.e. I can send and receive SMS. However, the eventual goal for me is to connect the board to Arduino MEGA and communicating with GM862. I read in the manual that in order to allow external communication the USB FTDI chip need to isolated from the evaluation board, via desoldering jumpers RX, TX, RTS, CTS. I was just wondering if anyone has done this, if so maybe someone can post a picture as to exactly where these jumpers are located. Also any comments interfacing the USB evaluation board for GM862 and Arduino MEGA would be greatly appreciated.