I have a few questions to unlock this module’s frequency bands for use in the USA. First off, I understand this module needs to be flashed with SIM900 firmware. The instructions I’ve found on flashing are very confusing. I understand there needs to be a TTL Level (USB /Serial) communication between the computer and module. I’m using a Bluetooth USB dongle in the laptop and a Sparkfun Bluetooth Silver Mate connected to the module for flashing.
First I need to know which port (com#) to connect to using my Sparkfun Bluetooth Silver Mate Antenna. I know this is specific to each computer and protocols available, but what is the easiest way to get the dongle and Bluetooth Silver Mate paired up?
Can I use AT commands between (Arduino’s serial monitor, BT dongle in PC) and (Bluetooth Antenna, GSM module) only?
Once I figure out which COM my Bluetooth Silver Mate and GSM module is on, then I can use the SIM900 Series Download Tool Develop 1.9.exe software to update my SIM900 firmware. HOWEVER, I’m stuck on step 1 and 3.
Step 1: Power up your SIM900A module to respond to AT commands in auto-baud mode (AT+IPR=0). It means you must wire powerlines, do power-on sequence with PWRKEY etc.
PWRKEY is a pin on the SIM900A. What exactly am I suppose to do here? This is where I’m stuck. Do I need a sketch running to use AT commands? What does it exactly mean to wire powerlines and do a power-on sequence with PWRKEY etc??
Step 3: Short NRESET (pin 16) to GND for a moment. Right after it reboots flashing tool will start pushing data.
Do I really need to temporarily solder on wire to the NRESET pin of the SIM900A for shorting to GND? Once I ground NRESET pin do I leave it grounded until the new firmware is installed or is this just a quick GND pin and release?
From what I understand if I had an Arduino board with the FT232 chip or a FT232 USB breakout board then I wouldn’t need to directly access pins on the SIM900A. Is that true? There is mention of an “Arduino approach”.
http://dostmuhammad.com/blog/sim900-firmware-update-tutorials-appnotes/