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Version: 6.x

Telemetry Injectors

Injectors bridge external sensors and scripts into the MAVLink stream as NAMED_VALUE_FLOAT / NAMED_VALUE_INT messages. Any connected ground station (QGroundControl, Mission Planner, fleet tools) sees the values as native telemetry, and they appear automatically in your Data Streams dashboards.

Find the page under Flight Controller → Injectors.

Why use Injectors​

Before Injectors, the common workaround was to abuse a Ground Control Station slot to push synthetic MAVLink into the stream. Injectors replace that hack with a first-class, listener-based pipeline that runs inside the Rust factory and auto-starts on boot, so injected signals keep flowing without any UI interaction.

Typical uses:

  • Companion-computer sensors: radiation, weather, gas, light, anything not native to the autopilot.
  • LTE / cellular signal stats (RSRP, SINR, RSSI) so the operator can monitor link quality in real time.
  • Custom scripts on the Pi that compute derived values (filtered, averaged, healthy / unhealthy flags).

Transport types​

Pick a transport when you add an injector. Type cannot be changed after creation; rotate or delete and recreate if you need to switch.

HTTP​

The injector exposes a unique URL with a secret token after creation. Any tool that can make an HTTP POST (curl, Python, an MCU with WiFi) sends JSON to that URL and the values flow into MAVLink.

  • Easiest to integrate, no port forwarding needed beyond what UAVcast already exposes.
  • Use Copy URL to grab the full endpoint, or Copy token only to plug into existing tooling.
  • Use Rotate token if you need to revoke the URL. Existing clients will start getting 401 immediately.

Example with curl:

curl -X POST https://your-uavcast/inject/<token> \
    -H "Content-Type: application/json" \
    -d '{"name": "RAD1", "value": 0.42}'

Batched form:

[
    {"name": "RAD1", "value": 0.42},
    {"name": "RAD2", "value": 0.51}
]

UDP​

The injector binds a port and receives line-delimited or JSON packets. Lowest overhead, no authentication, anyone who can reach the port can send. Good for trusted local networks (the Pi itself, a tethered companion, an Arduino on the same LAN).

  • Port: pick something unused. 14600 is a safe default.
  • Bind address: 0.0.0.0 to accept packets from other devices on the network, 127.0.0.1 to lock to the same machine.
  • Protocol: Key=Value (one signal per line as NAME=VALUE) or JSON ({"name":"X","value":1.23} per packet, or a batched array).

Serial​

The injector reads line-delimited samples from a tty device. Best for hardwired companion sensors (an Arduino over USB, an RS-232 sensor on a USB-to-Serial adapter).

  • Device path: /dev/ttyUSB0, /dev/ttyACM0, etc. Run ls /dev/tty* to discover.
  • Baud rate: must match the sender (9600, 57600, 115200 are common).
  • The injector reconnects automatically if the device unplugs.
dialout group

The user running uavcast-mavlink-manager needs access to the serial device. On Debian / Raspberry Pi OS that usually means adding the user to the dialout group:

sudo usermod -aG dialout <user>

Configuration fields​

Name​

A friendly label shown in the UI only. Does not affect MAVLink output.

Enabled​

Disable to keep the configuration but stop the listener. The HTTP endpoint will return 503, UDP and serial listeners are not bound.

MAVLink System ID, identifies which "vehicle" a message belongs to. The flight controller is usually sysid 1. Keeping injected values on the same sysid groups them with that vehicle in QGroundControl and Mission Planner. Range 1–255. Default 1.

MAVLink Component ID, identifies which device within the system sent the message. Range 0–255.

Common values:

  • 1 — autopilot
  • 25–50 — onboard companions
  • 190 — generic onboard sensor
  • 194 — popular choice for user payload sensors

Default 194.

Name prefix​

Optional. Automatically prepended to every signal name from this injector. Useful when multiple sources publish similar names: set BAL_ so an incoming RAD1 becomes BAL_RAD1 on the wire.

10-character cap

MAVLink hard-caps the total NAMED_VALUE_* name length at 10 characters, so keep the prefix short. The injector truncates anything beyond 10 characters.

Rate limit (Hz per signal)​

Maximum samples per second, per signal name. A sensor reporting at 100 Hz with rateLimit=10 gets 90 samples dropped silently. Protects the MAVLink bus from being saturated by a runaway source.

Sample formats​

Key=Value​

One signal per line:

RAD1=0.42
TEMP=21.5
LTE_RSRP=-92

Optional type suffix forces integer encoding (NAMED_VALUE_INT instead of NAMED_VALUE_FLOAT):

LTE_BAR:int=4

JSON​

Single sample:

{"name": "RAD1", "value": 0.42}

Batched:

[
    {"name": "RAD1", "value": 0.42},
    {"name": "TEMP", "value": 21.5}
]

Use "kind": "int" to force integer encoding:

{"name": "LTE_BAR", "value": 4, "kind": "int"}

Sending a test signal​

Each injector has a Send test signal action. Type a signal name and value, hit Send, and a single NAMED_VALUE_FLOAT (or INT) message will be emitted on the bus with the configured sysid / compid / prefix. The effective name after prefix is shown in the dialog.

Useful for confirming a ground station sees the value, or to seed a dashboard widget before the real sensor is wired up.

Stats​

Each injector card shows live counters refreshed every 2 seconds:

  • Accepted — samples that passed validation and were emitted on MAVLink.
  • Rate-limited — samples dropped because they exceeded the per-signal Hz cap.
  • Rejected — samples that failed parsing or sanitation (empty name, NaN value, etc.).

Counters survive listener restarts (configuration edits) but reset if the device reboots.

Viewing injected values​

Injected values appear automatically in the Data Streams dashboards under their configured names (with prefix applied). They are also forwarded to every connected Ground Control Station alongside normal flight controller telemetry.

Troubleshooting​

HTTP injection returns 404​

  • Double-check the token in the URL matches the one shown in the injector card. If you rotated the token, your client needs to be updated.
  • Confirm the injector is Enabled.

UDP packets sent but counters do not move​

  • Verify your sender targets the same port and host shown on the UDP endpoint card.
  • If you bound to 127.0.0.1 but are sending from another device, switch the bind address to 0.0.0.0.
  • Watch the Rejected counter: if it climbs, the payload is malformed. The Rust factory logs the reason.

Serial device not found​

  • Run ls /dev/tty* and confirm the device exists.
  • Confirm the running user is in the dialout group: groups | grep dialout.
  • Make sure no other process holds the port (a Mission Planner instance, a stale Arduino IDE).

Values appear in QGroundControl but not in Data Streams​

  • The widget binding looks for the effective name (prefix applied). Open the widget config and verify the name there matches what you see in QGroundControl.