OpenTag is a DASH7 protocol stack and minimal Real-Time Operating System (RTOS), written in the C programming language. It is designed to run on microcontrollers or radio Systems on a Chip (SoC). OpenTag was engineered to be a very compact software package. However, with proper configuration, it can also run in any POSIX environment. OpenTag can also provide all functionality required for any type of DASH7 Mode 2 device, rather than just the eponymous “tag”-type endpoint device.