Flash Programming Microcontrollers over the GSM Network

The following paper presents research and implementation of an over-the-air update of a 32-bit microcontroller through a low-cost GSM module. The objectives and aims are to enable long-distance updates of IoT devices connected to the GSM network. The flashing is accomplished with the help of UART bootloader that is entered on demand with the help of two separate pins. Data are transferred through the Internet. The proposed methodology includes the addition of a separate device that is connected to the target system and operates autonomously. The contribution to the field is to enable the usage of the ESP32 microcontroller in outdoor use. The benefit of such an approach is the optimized cost of the flashing device that is inherent from the core GSM module – the Ai Thinker A9G. The device has been deployed and working in a network of weather stations installed throughout a city in Bulgaria.