SEGGER RTT
More info
- Creator
- SEGGER Microcontroller
- Type
- Debug output protocol
Debug output written to a ring buffer in RAM and read by the debugger while the program keeps running.
RTT, Real Time Transfer, comes from Germany's SEGGER, maker of the J-Link. The idea is shamelessly simple. The firmware places a control block in RAM, tagged with the string "SEGGER RTT", alongside a set of ring buffers for data going up to the host and down to the target. The probe hunts down the block and reads the buffers through the debug port's background memory access, without ever halting the core.
A log line costs microseconds instead of the milliseconds semihosting takes, and it works on Cortex-M0 parts where SWO doesn't exist. The target-side code is permissively licensed, so OpenOCD and probe-rs implement the same protocol — the format has spread well beyond SEGGER's own probes.