Hi all,
just got my board off ebay and want to connect it first to my computer and then to arduino.
Problem started when I connected it to my usb to serial module and cannot get anything thgrough com port.
Standard settings was used 8N1(No flow CTR), baud 9600/115200/19200, nothing works.
I am powering module with 4.6V from outside.
Has any bought this one and possibly sucessfuly connected with PC/Arduino.
Thanks for helping out in advance.
When you get the communication working, please look at my article here, as you will not be able to use the SIM900A unless you are in asia (it is regional locked)
// Per.
I do not know if you got it working yet, but I have a similar module (ICStation SIM900 GSM Module). My first step is also to get it working connected to my PC first.
I am using the following USB to serial converter: FT232RL USB to Serial adapter module.
On the SIM900A module next to the antenna connector (which you highlighted as "possible interface selection?" in your image) is where you connect the module to the USB to serial adapter. I will use the following image as reference:
**Note:**The above image represents the one highlighted in your image, but your image is upside down in relation to the one above.
| **USB to Serial ** | SIM900A |
|---|---|
| GND | GND |
| TX | OVR |
| RX | OVT |
The above connection assumes the USB to Serial module operates at 5Vdc. I supply external power to the power connector (4.3Vdc).
@nikola1010: Hope this helps 
I got a SIM900 MINI v3.4.1 shield
I configured the voltage regulator at 4.0v and it works without problems with a SERIAL to USB adapter.
I'm still trying to use mu Arduino Mega to connect the shield, but no lucky. =(
