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Several features of Rotorflight require telemetry data for the motor speed such as the Govenor and RPM Filtering. One method for the FC to get this motor speed is via Bidirectional DSHOT. Bidirectional DSHOT is an ESC protocol which enables communications in both directions between the FC and the ESC. The speed command can be sent by the FC to the ESC and the ESC responds by sending the current motor eRPM (electrical RPM).

From the Motors tab in Rotorflight Configurator select an DSHOT ESC protocol (DSHOT150-DSHOT600) and enable Bidirectional DSHOT. This requires ESC firmware that supports Bidirectional DSHOT.

Supported ESC Firmware

BLHeli_32

Bidirectional DSHOT is fully supported from firmware version 32.7.0 onward. ESCs with earlier firmware will have to be updated before speed telemetry will operate.

BLHeli_S

BLHeli_S ESCs do not support Bidirectional DSHOT. In order to access this functionality with a BLheli_S ESC, alternative firmware must be flashed. There are currently 3 options for this.

1. Bluejay

Bluejay is an open source firmware for BLheli_S ESCs which supports Bidirectional DSHOT, see https://github.com/mathiasvr/bluejay. This firmware has been used successfully for several Rotorflight builds. Bluejay is capable of flashing individual settings to each ESC (tail and main) which is important when using an all in one (AIO) board. Bluejay v0.15 and later also supports disabling damped light (regenerative breaking), a must if your helicopter doesn't have a one way bearing. For example, a K110 will yaw/spin rapidly on throttle hold if damped light is enabled. See Flashing Bluejay for details.

2. BLheli_M

BLheli_M is developed by JazzMaverick. It supports Bidirectional DSHOT, but you can't disable damped light mode and it does not have the ability to download individual config to each ESC. JazzMaverick on GitHub.

3. JESC

Jesc is a paid firmware version for BLheli_S ESCs which supports Bidirectional DSHOT. Official website.

More information

More details on Bidirectional DSHOT and RPM filtering at betaflight .