Hello) I need a help) So, I bought the SIM900A module, but it works in Asian countries. Now im trying to make a firmware for that) For this, i need to connect with PL2303 TTL USB connector. The problem is, arter making the voltage on SIM900A through the Arduino uno, i try to conect my GSM module with USB connector (RX Connector to RX gsm module and TX the same). According to pin describtion on module i connected the wires, but the TX and RX LED on USB dont blinking) So, i made the randome changes and RX TX started to light) BTW, the module cannot react on AT commands.
When you use serial communication TTL or something your wire connection should be like this. Tx to Rx and Rx to Tx. Gnd to Gnd and Power to Power.
Do you have USB to TTL converter? Or use ardino for serial communication?
What is your county?
Yes, where are you using it? It is region locked to Asia. Its not quadband module.
Did you go through this checklist?