Developer turned budget 4G modem into portable messaging device

An engineer implemented a project to modify the 4G modem MF800 costing $20, turning it into a standalone communicator for exchanging text messages. The device received a physical Clicks keyboard and a compact Sharp display, running under a modified OpenStick Linux operating system.

To integrate the components, the development of a custom printed circuit board (PCB) was required, which provides correct power supply and switching of USB lines between peripherals and the modem. The hardware part of the device uses the capabilities of the OpenStick firmware, which allows running a full-fledged Linux distribution on Qualcomm MDM9x07 chipsets, which are usually installed in similar budget access points.

The software implementation includes writing an interface for processing SMS messages and managing the network connection through the modem's system calls. The project author noted that the main difficulty was optimizing power consumption when connecting external input-output modules to the modem's USB port, which was not initially designed to power third-party devices.

This development demonstrates the possibilities of reprofiling cheap network equipment into specialized terminals. The use of open drivers and a Linux kernel for LTE modems allows creating custom mobile devices with minimal costs, using standard communication protocols to transmit text data outside the usual smartphone ecosystems.