CRSF Sensors¶

CRSF Sensors is a dedicated listener for a CRSF-protocol sensor accessory (GPS, battery, barometer, per-cell voltage, or RPM module) wired to its own spare UART -- separate from the receiver link itself. It's for accessories that speak CRSF telemetry frames independently, not for reading data off your main RX link, and it's unrelated to Backup RX Input's own CRSF option, which is about failing over the control link, not reading a sensor.

Setting it up¶

Wire the sensor's data line to a spare UART, then assign that port the Bus: CRSF Sensors function from the port function dropdown on the Configuration tab's serial ports list. The port runs at CRSF's fixed baud rate -- there's nothing to pick.
If the sensor doesn't show data once wired, try flipping set crsf_sensors_pinswap = OFF (it defaults on, since real-world CRSF sensor accessories commonly wire up the opposite way round from this port's natural, un-swapped pin) -- then save and reboot.
Open the CRSF Sensors tab (Diagnostics group) to confirm it's actually receiving before wiring anything downstream to it -- see The diagnostic page below.

What it feeds, and how to enable it¶

Nothing downstream is enabled automatically just by wiring the sensor up -- each consumer needs its own source set explicitly:

GPS -- set GPS Protocol to CRSF on the GPS tab. With a CRSF Sensors port that is all GPS needs. Position, ground speed, heading, and satellite count come from the sensor's GPS frames.
Battery voltage/current -- set Voltage Meter Type and/or Current Meter Type to CRSF Sensor on the Power tab. See Battery source below for which frame type actually feeds the voltage reading when a sensor sends more than one kind.
Barometer altitude -- set crsf_sensors_use_baro = ON (CLI-only, not yet on this tab). This replaces an already-detected physical barometer's altitude reading with the sensor's each cycle -- it doesn't create a virtual barometer if no physical baro chip is fitted on the board at all.
RPM -- set crsf_sensors_use_rpm = ON (CLI-only). See RPM below -- this one comes with a real caveat, read it before wiring anything to it.

RPM¶

crsf_sensors_use_rpm = ON is a direct override, the same shape as crsf_sensors_use_baro: each motor's normal RPM value (whatever it would otherwise be -- DShot telemetry, a frequency sensor, none) is replaced with the sensor's decoded reading for that index, feeding straight into motor1Speed/motor2Speed (blackbox, OSD, this firmware's own outbound CRSF telemetry), RPM Filter, and the Governor's RPM modes alike. There's no separate protocol selection involved, and no ESC Telemetry setting on the Motors tab to touch.

Warning

This is telemetry-rate, not motor-rate. It is not a substitute for bidirectional DShot or a dedicated RPM/frequency-pin sensor, and use at your own risk applies if you turn this on while RPM Filter or the Governor's RPM Idle/Max or RPM Range modes are active -- see the Gyro tab's and the Governor's own notes on the same limitation. It's genuinely fine for OSD, blackbox, or telemetry display, where the update rate doesn't matter.

Only voltage/current has a source-selection setting (crsf_sensors_battery_source, below) -- RPM has nothing else to choose between, since only one CRSF frame type carries it.

Battery source¶

A sensor can report battery data as an aggregate frame (voltage, current, capacity used, and remaining % all together) or as a set of individual cell voltages with no current data -- some sensors only ever send one or the other, and a few devices marketed as separate "current sensor" and "cell voltage sensor" products exist specifically because of that split. crsf_sensors_battery_source (CLI-only) picks which one feeds Voltage Meter Type = CRSF Sensor on the Power tab:

Value	Behavior
`AUTO` (default)	Prefer the aggregate frame; fall back to summed cell voltages only if the aggregate one isn't present.
`CURRENT`	Always use the aggregate frame, no fallback -- named for the field only it has, since the cell-voltage frame carries no current data at all.
`VOLTAGE`	Always use summed cell voltages, even if an aggregate frame is also present on the bus.

Current always comes from the aggregate frame regardless of this setting -- there's nowhere else for it to come from.

Note

If an individual cell reads back an implausible value (tens of volts on a single tap -- almost always a bad connector/balance-lead connection on the sensor itself, not a wiring or firmware issue), that one channel is excluded from the pack total rather than corrupting it. The resulting total will read low by roughly that cell's worth until the connection is fixed, rather than showing a dangerously wrong high reading.

The diagnostic page¶

The tab only appears once a port is assigned the CRSF Sensors function, and polls twice a second:

Link -- whether the port opened, plus raw byte/sync/CRC counters. Bytes-received-but-zero-sync-frames points at a baud/protocol mismatch on the wire; sync-frames-but-zero-CRC-OK points at signal integrity issues; both at zero with a powered, wired sensor points at the physical connection itself (wrong pin, no shared ground, or genuinely not a CRSF device).
GPS / Battery / Barometer / Cell Voltages / RPM -- each shows a Receiving or No data badge and the latest decoded values for whichever frame types the sensor actually sends. A card reading "No data" just means that particular frame type has never arrived -- most sensor accessories only send one or two of the five types this feature understands.

Only five CRSF frame types are decoded: GPS (0x02), RPM (0x0C), the aggregate Battery Sensor (0x08), Altitude/vario (0x09), and per-cell Voltages (0x0E, per the TBS CRSF spec). Anything else on the wire is safely ignored.

CLI settings¶

Setting	Default	Meaning
`crsf_sensors_timeout_ms`	`2000`	How long without a fresh frame before that sensor's data is dropped as stale. Range 500-10000. CLI-only.
`crsf_sensors_use_baro`	`OFF`	Replace a physical barometer's altitude reading with the sensor's, see above. CLI-only.
`crsf_sensors_pinswap`	`ON`	Swap which physical pin this UART uses for RX, see Setting it up. CLI-only.
`crsf_sensors_battery_source`	`AUTO`	Which frame type feeds Voltage Meter Type = CRSF Sensor, see Battery source. CLI-only.
`crsf_sensors_use_rpm`	`OFF`	Override each motor's RPM with the sensor's reading -- see RPM for the important caveat before using this for filtering or governing. CLI-only.

None of these are on the Configurator UI yet -- set them from the CLI, then save.