Flash SimCom SIM900A Firmware

22 May 2022

Appearantly, the “A” in SimCom’s SIM900A GPRS/GSM Modem Module stands for “Asia”, which means it’s not usable in mobile networks outside of Asia, but it’s possible to flash a different firmware to make it work globally.

Requirements

• Windows PC (or VM)
• USB to UART Bridge (tested with CP2101)
• SIM900 Custom Flash Loader v1.01 (download here)
• SIM900 ENHANCED Firmware (download here)
• PuTTY

Flashing the Firmware

1. Connect the SIM900A Module to the USB UART Bridge
2. Open Windows Device Manager to find the UART Bridge’s serial port number (e.g. COM3):
3. Run PuTTY to establish a serial connection to the SIM900A:
4. Set the SIM900A’s fixed baudrate to 19200 by sending the AT+IPR=19200 to the modem:
5. Quit PuTTY to close the serial line.
6. Run the SIM900 Custom Flash Loader tool and select the firmware file, the appropriate COM Port and set the line speed to 19200 baud.
7. Press START and restart the SIM900A (power off & on again). This starts the flashing process. The flashing process can take up to 30 minutes:

1. https://www.mikrocontroller.net/articles/Sim900#Firmware_Flashen
2. https://simcom.ee/documents/?dir=SIM900
3. https://web.archive.org/web/20161130132417/http://www.geekonfire.com/wiki/index.php?title=GPRS_Shield%EF%BC%88SIM900%EF%BC%89_Firmware_Update