Quick Answer
ELRS telemetry sends flight data from your drone back to your radio controller, including battery voltage, current draw, RSSI signal strength, and GPS coordinates if available. Enabling it requires wiring the receiver's TX pad to a spare UART RX on your flight controller, then enabling telemetry in Betaflight's configuration.
What ELRS Telemetry Gives You
Without telemetry, your radio only knows if it has a connection to the drone. With telemetry enabled, ELRS sends a stream of data back from the flight controller through the receiver. This includes:
| Data Type | What It Shows |
|---|---|
| RSSI | Signal strength between radio and receiver |
| Battery voltage | Real-time voltage of your flight pack |
| Current draw | Amps being pulled by motors and electronics |
| Used capacity | mAh consumed so far in the flight |
| GPS (if equipped) | Position, speed, altitude, and distance from home |
This information displays on your radio screen or in your radio controller's telemetry menu. It is useful for monitoring battery level mid-flight and landing before voltage drops too low.
Hardware: Wiring It Up
ELRS telemetry requires a two-way connection between the receiver and the flight controller. The receiver's TX pad carries telemetry data out, so it needs to connect to a UART RX pad on the FC. The receiver's RX pad receives RC commands from the FC's UART TX.
You need a full UART pair (both TX and RX wires). Some smaller receivers like the iFlight ELRS Nano break out both pads on the connector. Others may require soldering a wire. Check the receiver's pinout diagram before wiring.
If you are using an AIO flight controller with a built-in ELRS receiver like the Happymodel CrazyF4 ELRS 868MHz AIO, telemetry is wired internally. You just need to enable it in the configurator.
Betaflight Configuration
Once the hardware is wired, open the Betaflight Configurator and configure the UART:
- Go to the Ports tab and find the UART where your receiver is connected.
- Enable Serial RX on that UART.
- Set the telemetry baud rate to match ELRS (typically 420000 or 115200, depending on your ELRS version).
- Go to the Configuration tab.
- Set Receiver mode to Serial, and Serial Receiver Provider to CRSF.
- Set Telemetry to Enabled.
- Set RSSI Channel to Disabled (ELRS provides RSSI via telemetry, not a separate channel).
Save and reboot. Your radio should now show voltage and other telemetry data if the wiring is correct.
ELRS Lua Script: Receiver Configuration
The ELRS Lua script on your radio lets you enable or disable specific telemetry sensors to manage the data rate. Higher telemetry ratios consume more bandwidth, which can slightly reduce RC link performance. For most flying, the default 1:128 ratio works well. If you are doing long-range flights where link budget matters, reducing the telemetry ratio helps.
Access the Lua script from your radio's Tools menu. Navigate to the Telemetry section and adjust the ratio if needed.
Choosing the Right Receiver
Most ELRS receivers support telemetry, but check the specifications before buying. Standalone receivers like the RadioMaster ER5A V2 and iFlight Diversity receiver both support full telemetry out of the box. Diversity receivers like the iFlight use two antennas for better signal reliability, which is worth the extra cost if you fly in areas with potential multipath interference.
Browse the full radio receivers collection to compare ELRS options across form factors and frequencies.
Common Problems
Telemetry shows dashes or no data: Check the wiring between the receiver TX pad and the FC UART RX pad. A loose or missing wire is the most common cause. Also verify you have enabled telemetry in Betaflight, not just the UART.
Voltage reading is wrong: The flight controller reads voltage via its voltage sensor (or OSD chip), not the receiver. Calibrate it in the OSD tab. If the reading is zero, check that the FC is connected to the battery voltage sense pad or main power leads.
Intermittent connection: If enabling telemetry causes link instability, reduce the telemetry ratio in the Lua script. If the problem persists, ensure the UART is configured as full-duplex and uninverted. Run get serialrx in the Betaflight CLI and confirm serialrx_inverted = OFF and serialrx_halfduplex = OFF.
For a broader look at setting up ELRS from scratch, including binding and firmware flashing, see our RadioMaster Pocket ELRS setup guide. If you are interested in adding long-range control to an existing transmitter, our TXMOD guide covers that in detail.