Glossary · 5 · Hardware SDKs and devices
Debug probe
Also known as: Debug adapter, Debug unit, JTAG adapter, In-circuit debugger
In embedded systems, a debug probe is a hardware adapter that connects a development computer, usually over USB or Ethernet, to the debug port of a target processor, typically JTAG or Serial Wire Debug, so that a debugger can load programs into the target's memory, control execution and read registers and memory.
- Hardware SDK
- Embedded systems
In one sentence
A debug probe connects a development computer to a target processor's debug port (JTAG, SWD) for flashing, run control and inspecting memory.
Example
A developer connects a debug probe to the two-pin SWD header of a microcontroller board, flashes a new build and stops the program at a breakpoint to read a sensor register.
How it applies
- Hardware SDKs: A debug probe is the physical link in the workflow of a hardware kit: cross-compile on the development computer, flash the binary through the probe, then run and inspect it on the target with a debugger (see debugging). Many evaluation boards integrate a probe so that one USB cable is enough.
- Debug ports: The two common interfaces are JTAG, standardized as IEEE Std 1149.1 (Test Access Port and Boundary-Scan Architecture), and Arm's two-pin Serial Wire Debug (SWD). Arm's CMSIS-DAP documentation describes a debug access port reached either through 5-pin JTAG or 2-pin SWD and connected to a debug unit.
- Probe firmware and protocols: The probe runs firmware that translates between the host connection and the debug port. CMSIS-DAP, for example, is the interface firmware for a debug unit that connects the debug port to USB and gives debuggers on the host a standardized interface.
- Trace: Some probes also capture trace output (for example Serial Wire Output on Cortex-M devices), which records program flow without stopping the target.
- Documentation: State which debug interfaces a board exposes, the connector pinout, the supported probes and host tools, and whether the debug port is locked in production devices. Whether a debug port may stay open in the field is a security decision for the product's risk assessment, not for the probe documentation.
Debug probe vs. debugger
The probe is hardware: it carries signals between the computer and the target. The debugger is the software that uses the probe to set breakpoints, step through code and show memory. One probe can serve several debuggers, and one debugger can drive several kinds of probe.