Interface SIM900a A6 module with Arduino

I’m trying to interface SIM900a A6 module like the one shown in the link below with Arduino Leonardo. Based on the blinking status of the onboard LEDs of the SIM module (blinks continuously every 3s), the sim should be connected to the network. However, when I call the SIM number inserted in the module I don’t hear a ring back. It also doesn’t respond to AT commands.

Hardware connection:

I’m connecting it to 5V from Arduino board. Rx to pin#2 and Tx to pin#3.

Kindly help me understand why it’s not working!! Thank you

Hi !
You must try to communicate with AT commands before hope to make calls.
The 5V on arduino board, if powered by USB connection, is not enough.
You have to get 5V for the SIM module elsewhere, like from a recent cellphone charger or power bank beyond 2A (2000mA).
You must have GND of the power source and GND of communication together.
You can start with a little sketch just to begin with AT commands, then a sketch to send SMS, then to give a call.
If there is no AT response at all, check/reverse RX and TX connections.
IF there is response but strange, check baudrate.
And go there :


Sorry for my english, i’m french.
Regards, David.
1 Like

Go through this Post First:

and then Go through this post:

May be you might get some Idea.

1 Like

Hello,
This particular module requires 3.3V TTL levels (and proper power using 5V 1-2A phone microUSB charger for example). You would need either level shifting or an Arduino working at 3.3V.
If you use 5V TTL levels, you will see the message from A6 but will not be able to send any AT commands.
Raz.