HARDWARIO Real Time Transfer Terminal Console

Overview

HARDWARIO Real Time Transfer Terminal Console (rttt) is a Python package that provides an interface for real-time data transfer using SEGGER J-Link RTT (Real-Time Transfer) technology. It enables efficient data communication between an embedded system and a host computer via RTT channels.

This package is particularly useful for debugging, logging, and real-time data visualization in embedded applications.

Features

• Real-time communication with embedded devices via RTT.
• Support for multiple RTT buffers (console and logger).
• Adjustable latency for optimized readout.
• J-Link support with configurable serial numbers, device types, and speeds.
• Command-line interface (CLI) for quick and easy access.
• Easy installation via PyPI.

Installation

To install the package, use:

pip install rttt

To verify the installation, run:

rttt --help

Usage

Basic Command

To start the RTT console:

rttt --device <DEVICE_NAME>

Available Options

Usage: rttt [OPTIONS]

  HARDWARIO Real Time Transfer Terminal Console.

Options:
  --version                  Show the version and exit.
  --serial SERIAL_NUMBER     J-Link serial number, or DEMO for the demo probe.
  --demo                     Use the built-in demo probe (same as --serial DEMO).
  --device DEVICE            J-Link Device name.
  --speed SPEED              J-Link clock speed in kHz. [default: 2000]
  --reset                    Reset application firmware.
  --flash-cmd COMMAND        External command used by the flash operation
                             instead of the built-in J-Link programming.
                             Must contain the {file} placeholder.
  --address ADDRESS          RTT block address.
  --terminal-buffer INTEGER  RTT Terminal buffer index. [default: 0]
  --logger-buffer INTEGER    RTT Logger buffer index. [default: 1]
  --latency INTEGER          Latency for RTT readout in ms. [default: 50]
  --history-file PATH        Path to history file. [default: ~/.rttt_history]
  --console-file PATH        Path to console file. [default: ~/.rttt_console]
  --mcp / --no-mcp           Enable MCP server. [default: no-mcp]
  --mcp-listen TEXT          MCP server listen address [host:]port. [default: 127.0.0.1:8090]
  --mcp-token TOKEN          Require "Authorization: Bearer TOKEN" on the MCP
                             server and upload endpoint.
  --substitutions / --no-substitutions
                             Enable template substitutions in terminal input.
                             [default: substitutions]
  --trust-shells             Trust shell substitutions in config without
                             interactive prompt (for CI/scripts).
  --headless                 Run without the interactive console, MCP server
                             only (requires --mcp).
  --help                     Show this message and exit.

Examples

Connect to a device (replace NRF52840_xxAA with your actual device name):

rttt --device NRF52840_xxAA

Use a specific J-Link serial number:

rttt --device NRF52840_xxAA --serial 123456789

Demo probe (no hardware)

For GUI development without a J-Link, select the built-in demo probe by serial number (same CLI path as a real probe):

rttt --serial DEMO
# or
rttt --demo

The demo emits synthetic terminal/log lines, reports CONN connected, and supports reconnect via F4, the overlay Reconnect button, or by typing reconnect in the command field. Type disconnect to simulate a drop and exercise the Connection overlay (output pauses until reconnect succeeds).

Demo commands (type into Command, then Enter):

Clipboard (SSH / tmux)

Copy uses a hybrid clipboard: OSC 52 (works over SSH into the local terminal) plus pyperclip when a local GUI display is available. Select text with the mouse to auto-copy from one pane only (Interactive Terminal or Device Log — never both merged). A real drag (mouse move with the button held) auto-pauses scroll so streaming lines do not jump the viewport; a plain click does not pause. While paused (manual F5 or auto during drag / keyboard selection), the status bar shows a highlighted PAUSED marker and the F5 hint switches to F5 Resume (back to F5 Pause when streaming). After a successful select-to-copy, if scroll was running before the selection, streaming auto-resumes and the highlight clears (toast Copied N chars — resumed). If you had paused with F5 first, the pause and highlight stay so you can keep reading. Toasts appear on the right of the status bar, temporarily replacing the clock (left hints stay visible; pane heights do not change). Ctrl-C / Ctrl-Insert copies the focused pane's selection (or re-toasts the last single-pane copy). Shift+Arrows / Home / End / PageUp / PageDown and Ctrl-A extend or select-all in the focused Log/Terminal pane (Command keeps its normal editing keys). Many terminals (including xfce4-terminal) steal Shift+Up/Down and Shift+PageUp/Down for their own scrollback, so those keys never reach rttt — use Shift+Left/Right (they already cross line boundaries) or the mouse instead. The first keyboard extension while streaming auto-pauses like a drag, and Esc clears the highlight (and auto-resumes only if the pause was automatic — never after F5). Right-click copy uses the same auto/manual resume rules as Ctrl-C. F6 toggles mouse reporting off so the terminal emulator's own selection works across panes or when the in-app clipboard path is unavailable (Connection overlay still forces mouse on for its buttons). Right-click on Log/Terminal copies the selection in that pane (same path as Ctrl-C; no selection → re-toast last copy or Nothing selected). Right-click on the Command line pastes (local pyperclip when available; otherwise the in-app last copy — no OSC 52 clipboard read). Multi-line paste keeps the first line only (Command is single-line). Hold Shift while dragging for the terminal's native selection when the emulator supports that bypass. Exit with Ctrl-Q if F10 is captured by the desktop (e.g. XFCE).

Over SSH, pyperclip alone fails because it talks to the remote machine — rttt skips it when SSH_CONNECTION / SSH_CLIENT is set and relies on OSC 52. Prefer a terminal with OSC 52 enabled. With tmux, allow passthrough, for example:

set -g set-clipboard on
# or allow OSC 52 through: set -g allow-passthrough on   # tmux >= 3.3

Verify OSC 52 over SSH: from a local machine with clipboard tools, SSH in, run rttt --demo, select a known string, then on the local host check the clipboard (pbpaste / xclip -o / paste into an editor). Unit tests cover the SSH path by setting SSH_CONNECTION and asserting the OSC 52 escape sequence (including tmux DCS wrapping) without needing a real remote session.

On a local Linux desktop without a working OSC 52 terminal, pyperclip needs a clipboard helper such as xclip or xsel (install separately, e.g. sudo apt install xclip). They are not a hard dependency of rttt.

GUI retest checklist (mouse / clipboard / selection)

Unit tests cover HybridClipboard and selection helpers. A PTY integration suite (tests/test_tui_pty.py) additionally spawns rttt --demo under a pseudo-terminal, renders with pyte, injects real xterm SGR mouse sequences, and asserts OSC 52 clipboard payloads — run it with the rest of the suite (pytest). Those tests skip automatically where pty is unavailable (e.g. Windows CI).

A green pytest run is still not enough after mouse / toast / clipboard changes: also retest in a real terminal (desktop or SSH). The PTY harness does not cover every emulator quirk (VTE OSC 52 limits, Shift-drag native selection, desktop key grabs like F10).

rttt --demo
# or: pytest tests/test_tui_pty.py -v

Manual checklist:

1. First drag (app just started, Command focused): slow-drag in Log or Terminal → toast Copied N chars — resumed, highlight clears, scroll running again. Must not stop at only Paused for selection.
2. Focus switch: after selecting in Log, the first drag in Terminal (and the other way around) must copy on that same gesture — not only move focus.
3. Selection start: press on line N, release on line N+k → highlight/copy starts on line N (not near the bottom / old scroll tip). End follows the release point.
4. Plain click (no drag): stream stays running; no 1-cell highlight; no pause toast.
5. After F5 resume: first drag again still copies and auto-resumes.
6. Manual F5 then drag: press F5 → status bar shows PAUSED and F5 Resume; then drag-copy → stays paused, highlight sticks, toast without — resumed (still PAUSED).
7. Streaming mid-drag: with lines flying, drag still selects and copies (auto-pause on move, not press); PAUSED appears during the drag, then clears on auto-resume. Toast must include — resumed when scroll was on before the drag.
8. One pane only: selection in Log must not merge Terminal text (and vice versa).
9. Ctrl-C / Ctrl-Insert: after auto-resume (no highlight), re-toasts the last single-pane copy inside the status bar (pane heights must not jump).
10. Toast layout: while a toast is visible, both panes stay the same height as without a toast. Toast appears on the right (replacing the clock); left hints stay visible; when it expires the clock returns.
11. Local clipboard: xclip -o / pbpaste (or paste into an editor) shows the copied text.
12. SSH / OSC 52 (when available): select in remote rttt --demo, paste on the local host.
13. Reconnect: F4 / overlay button / typed reconnect; disconnect silences demo output until reconnect.
14. Right-click copy: with a sticky highlight (e.g. after F5 + drag), right-click in that pane → Copied N chars; streaming/pause state unchanged; focus stays put. With no selection and a prior copy → re-toast; with nothing ever copied → Nothing selected.
15. Right-click paste: right-click the Command line → focuses Command, inserts clipboard text (trailing newline stripped; first line only if multi-line), toast Pasted N chars or Clipboard empty. Over SSH, paste uses the last in-app copy (select something first).
16. F6 mouse toggle: press F6 → status shows F6 Mouse OFF, terminal native drag-select works; F6 again restores in-app mouse. With mouse off, open a disconnect overlay → buttons still clickable (mouse forced on).
17. Keyboard selection: focus Log or Terminal (F3/Tab/click), Shift+Up/Down/Left/Right (also Home/End, PageUp/PageDown) or Ctrl-A → PAUSED, highlight grows by lines/chars; Ctrl-C or right-click → Copied N chars — resumed when the pause was automatic. After F5 first, keyboard/RMB copy stays PAUSED (no — resumed); Esc clears highlight and only auto-pause resumes (manual F5 never lifted by Esc/copy/select). On the Command line, Ctrl-A / Shift+arrows / Ctrl-U still edit normally.
18. Line-number gutter drag: press on the Log/Terminal line-number margin, drag into text, release → copy starts on that line (not from the bottom); toast includes — resumed when scroll was on; no stuck highlight without PAUSED.
19. Toast on the right: after a copy/paste, the message (Copied N chars, — resumed, Pasted N chars, …) appears on the right where the clock usually is; F5/F6 hints on the left stay readable; when the toast expires the clock comes back.

Limits: some VTE-based terminals (older GNOME Terminal) ignore or cap OSC 52; very large selections are truncated (~60k characters).

Configuration File

RTTT supports configuration via .rttt.yaml files. All existing files are loaded and deep-merged, so you can keep user-wide defaults in your home directory and override specific keys per project. The load order, from lowest to highest priority, is:

1. ~/.config/rttt.yaml — user defaults
2. ~/.rttt.yaml — user defaults (alternative location)
3. ./.rttt.yaml — project-specific overrides
4. RTTT_* environment variables
5. Command-line flags

Nested mappings (like substitutions:) merge per-key — a project config can add new substitutions without losing the ones defined in your home config, or override specific ones by name.

Example Configuration:

device: NRF9151_XXCA
console_file: "test.log"
substitutions:
  RTC_SET: "rtc set {{UTC_NOW}}"

With this configuration, simply running:

rttt

Input Substitutions

RTTT can expand {{NAME}} placeholders in commands you type in the terminal before they are sent to the device. This is handy for things like setting the current time on the device without typing it manually:

rtc set {{UTC_NOW}}

gets expanded to (example):

rtc set 2026/04/20 10:08:00

Built-in Substitutions

Placeholder names must be upper-case letters, digits, and underscores, and start with a letter or underscore.

Custom Substitutions

Define your own values in .rttt.yaml under the substitutions key. Values are strings and may reference other substitutions (built-in or custom):

substitutions:
  RTC_SET: "rtc set {{UTC_NOW}}"
  PROJECT: "nrf9151-demo"
  HEADER: "DEV={{PROJECT}} T={{UTC_NOW}}"

Then typing {{RTC_SET}} in the terminal sends e.g. rtc set 2026/04/20 10:08:00 to the device.

Custom names take precedence over built-ins, so you can override UTC_NOW with a fixed value if needed.

Multi-Line Substitutions

A substitution value may contain newlines. When the expanded text spans multiple lines, each line is sent as a separate input event to the device. This is useful for grouping a batch of commands under a single placeholder:

substitutions:
  CONFIG: |
    app config interval-sample 60
    app config interval-aggreg 300
    app config interval-report 1800
    {{RTC_SET}}

Typing {{CONFIG}} sends all five commands in order. Nested placeholders (like {{RTC_SET}} above) are expanded recursively before the fan-out.

Shell Substitutions

A substitution value can also be a shell command, evaluated lazily each time the placeholder is expanded:

substitutions:
  GIT_SHA:
    shell: "git rev-parse --short HEAD"
  BUILD_HEADER: "build={{GIT_SHA}} at {{UTC_NOW}}"

Options for a shell: entry:

Commands have a 5 second timeout. On failure (non-zero exit, timeout, or missing binary), the placeholder is left in the text and a warning is logged.

Trust prompt. Because a .rttt.yaml in a project you didn't write could run commands on your machine, rttt asks for confirmation the first time it sees a new set of shell substitutions. The approval is cached in ~/.hardwario/rttt_allowed_shells as a hash of the command list plus the absolute config path — you only get asked again if the commands actually change. For non-interactive use (CI, scripts), pass --trust-shells to skip the prompt.

Enabling / Disabling

Substitutions are enabled by default, so built-ins like {{UTC_NOW}} work out of the box. Use --no-substitutions on the command line to disable them for a single session (for example if you actually need to send the literal text {{UTC_NOW}} to the device).

Errors

If a placeholder name is unknown, references itself (cycle), or the format string fails, the placeholder is left in the text as-is and a warning is written to ~/.hardwario/rttt.log. The command is still sent to the device so you don't lose keystrokes.

MCP Server (AI Integration)

RTTT includes a built-in Model Context Protocol (MCP) server that allows AI tools (Claude, Cursor, etc.) to interact with your embedded device via RTT.

MCP server is enabled by default. Start RTTT as usual:

rttt --device NRF52840_xxAA --mcp

Claude Code Configuration

Add to your .mcp.json:

{
    "mcpServers": {
        "rttt": {
            "type": "http",
            "url": "http://127.0.0.1:8090/mcp"
        }
    }
}

When the server runs with --mcp-token, add the matching header:

{
    "mcpServers": {
        "rttt": {
            "type": "http",
            "url": "http://127.0.0.1:8090/mcp",
            "headers": {
                "Authorization": "Bearer <TOKEN>"
            }
        }
    }
}

Authentication

By default the MCP server has no authentication and binds to 127.0.0.1, which is fine for local use. When exposing it to a network (e.g. --mcp-listen 0.0.0.0:8090 on a shared debug box), set a token:

rttt --device NRF9151_XXCA --mcp --mcp-token "$(openssl rand -hex 16)"

Every HTTP request — both the /mcp endpoint and /upload — must then carry Authorization: Bearer <TOKEN>; anything else gets 401 Unauthorized. The token can also come from the RTTT_MCP_TOKEN environment variable or the mcp_token key in .rttt.yaml. Note the transport is plain HTTP, so on an untrusted network the token (and everything else) is visible on the wire — use an SSH tunnel or a TLS reverse proxy for anything beyond a lab LAN.

Available MCP Tools

The server also exposes a debug_device MCP prompt describing typical debugging workflows and RTT troubleshooting for agent clients.

External Flash Command

By default the flash operation programs the device through the J-Link DLL. When a different tool works better for your target (e.g. nrfjprog for nRF91, hardwario CLI, west flash), override it with --flash-cmd or the flash_cmd key in .rttt.yaml:

rttt --device NRF9151_XXCA --mcp \
     --flash-cmd 'nrfjprog --family NRF91 --program {file} --sectorerase --verify --reset'

flash_cmd: "nrfjprog --family NRF91 --program {file} --sectorerase --verify --reset"

The command runs through the shell with these placeholders (values are shell-quoted automatically):

The J-Link connection is released for the duration of the command so the external tool can claim the debug probe, and RTT re-attaches afterwards. The tool's output is streamed to the console and log. With an external command the .zip extension is also accepted (nrfjprog modem firmware packages).

Because flash_cmd from a config file is an arbitrary shell command, it goes through the same trust prompt as shell substitutions — you approve it once per config file (or pass --trust-shells in CI).

Headless Mode

For CI boxes, remote debug servers or fully agent-driven sessions, run the MCP server without the interactive console:

rttt --device NRF9151_XXCA --mcp --headless

Uploading Firmware from a Remote Client

The flash tool resolves paths on the machine rttt runs on. When the MCP client runs elsewhere, upload the firmware first via the HTTP endpoint served on the same port:

curl --data-binary @fw.hex 'http://<host>:8090/upload?filename=fw.hex'
# → {"status": "ok", "path": "/tmp/rttt-uploads-8090/fw.hex", "size": 123456}

Then pass the returned path to the flash tool. Allowed extensions are .hex, .bin, .elf and .srec; the body is limited to 64 MiB.

With --mcp-token set, include the header:

curl -H 'Authorization: Bearer <TOKEN>' \
     --data-binary @fw.hex 'http://<host>:8090/upload?filename=fw.hex'

Note: without --mcp-token the MCP server and the upload endpoint have no authentication. The default bind is 127.0.0.1; set a token before exposing them with --mcp-listen 0.0.0.0:8090 outside a trusted network (see Authentication).

License

This project is licensed under the MIT License - see the LICENSE file for details.

Made with ❤  by HARDWARIO a.s. in the heart of Europe.