Scan for connected PROBES — the debuggers plugged into this machine, not target chips. Despite the name it does not list target devices; use search_devices for those. Shows probe serial numbers and whether one is reachable.

Check that everything needed to debug is in place: the probe software, a connected probe, a target device name, and the optional files that make output readable. Run this first when anything fails, or when starting on a machine for the first time.

Point the server at a CMSIS-SVD file for the target at runtime, so peripheral reads come back with named fields and decoded values instead of raw hex. Mirrors set_device — you do not have to restart with SVD_PATH set.

Tell the server where the firmware's RTT control block is (its _SEGGER_RTT symbol), at runtime. Without it RTT cannot be recovered after a reset or flash, and a stopped stream is indistinguishable from a quiet device. Mirrors set_device.

Search the device names this J-Link installation accepts, by part number, manufacturer, or core. Use this before set_device instead of guessing a part number — the name must match exactly, and a wrong one fails in a way that looks like broken hardware.

Set the target device name at runtime. Required before any debugging commands will work. The name must match J-Link's exactly — use search_devices to find it rather than guessing a part number. Examples: 'nRF52840_XXAA', 'nRF5340_xxAA_APP', 'STM32F407VG', 'STM32L476RG'.

One-call setup: starts GDB server via SEGGER J-Link, connects RTT (if supported), waits for initial output. This is the recommended first tool to call. If no device is configured, use list_devices and set_device first.

Capture complete device state: CPU registers (compact), fault status, recent RTT output, and stack dump.

Auto-read and decode ARM Cortex-M fault registers (CFSR, HFSR, MMFAR, BFAR), exception stack frame, and recent errors.

Halt the target and read its registers via SEGGER J-Link. Returns the probe name and a compact register summary. Leaves the target HALTED — call resume when you are done.

Halt the target CPU

Resume the target CPU

Reset the target device. Halting leaves the core stopped at the reset vector, which is where you want it before flashing, or to watch startup run.

Step one CPU instruction

Read memory from the target. Returns clean hex dump.

Write a 32-bit value to memory

Read all CPU registers (compact format, FP only if non-zero).

Read a specific CPU register by name

Flash firmware to the target device

Erase target flash memory

List the target's peripherals and base addresses, from its CMSIS-SVD description. Requires an SVD file to be configured.

Read every register of a peripheral from the target and decode each one's bit fields by name. This is read_memory plus the meaning of what was read.

Decode a value into named bit fields using the target's SVD. Reads from the device unless a value is supplied — useful for interpreting a number you already have.

Set a hardware breakpoint

Clear all breakpoints, including any left armed in the debug hardware by an earlier session

Start SEGGER J-Link GDB server

Stop SEGGER J-Link GDB server and disconnect RTT

Get GDB server, RTT, and telnet proxy status

Connect a GDB client to the running GDB server. Enables source-level debugging: backtraces, variable inspection, conditional breakpoints, stepping by source line. Optionally load an ELF file for symbol info.

Send any GDB command and get the response. For execution commands (continue, step, next, finish, until), blocks until the target stops or times out. If the target doesn't stop, use gdb_wait to poll. Examples: 'bt' (backtrace), 'info threads', 'print myVar', 'break main', 'continue', 'next', 'step', 'finish', 'info registers', 'x/10xw 0x20000000'

Poll for target stop after a continue/step that timed out. Returns the stop reason (breakpoint hit, signal, finished stepping, etc.) when the target halts.

Load an ELF file into GDB. By default loads symbols only (for source-level debugging: backtraces with file:line, variable names). Set flash=true to also program it onto the target.

Get a stack backtrace. With debug symbols loaded, shows function names, file paths, and line numbers.

Disconnect the GDB client (does not stop the GDB server)

Connect to RTT

Disconnect from RTT

Read RTT log lines (clean, parsed Zephyr format). Non-destructive — reading does not consume the buffer. Returns the NEWEST lines by default; oldest:true returns the start of the buffer. Note the buffer spans reflashes: its oldest lines may be from firmware you have since replaced. rtt_clear drops them.

Search/filter RTT logs by level, module, or regex

Send data to device via RTT down-channel

Read SEGGER's RTT control block on the target: is it initialised, how much has the firmware written, and how much has the probe collected. Use this when RTT is silent — it separates a quiet device from a probe that stopped collecting, which look identical from rtt_read.

Clear RTT buffer

Start a TCP relay that re-serves the RTT stream on another port, so an external decoder (Trice, Pigweed, or your own) can consume it alongside this server. It relays bytes; it does not decode them.

Stop telnet proxy

Get telnet proxy status

Read raw data from telnet proxy buffer

Execute raw SEGGER J-Link commands

Get current probe and server configuration