With the introduction of Betaflight 4.1 / 4.2 many people are talking about RPM Filtering, so let us shed some light on it and give you some tips on getting RPM filtering working on your quad.
Is RPM Filtering Safe?
Although it feels very new it is a feature that has been in development for quite some time and can be considered to be in a very stable state and safe to use.
What is RPM Filtering?
RPM filtering uses the bi-directional Dshot information to know exactly what rpm each motor is at a given time and therefore be able to set very accurate notch filtering that dynamically follows each motor noise profile as the rpm increases / decreases. It works very well at reducing hot motors in situations with slightly bent props etc.
Can I Use RPM Filtering?
If your quad is running blheli32 esc's there is no cost involved to enable bi-direction dshot. You just need to have your esc on one of the latest versions of firmware and use the latest version of betaflight (4.1 or newer) on your flight controller.
If you have blheli_s esc it takes a little more work to get rpm filtering. Firmware from JESC allows you to have telemetry enabled but there is a cost per esc to enable this feature we have found our micros fly fantastic on the JESC 48K firmware with telemetry giving us longer flight times and some piece of mind with cool motor temperatures.
How do I know if RPM Filtering is active on my quad?
Goto the motors tab in betaflight and spin up your motor. Underneath the Throttle number you should see your exact RPM of the motor like the below screenshot.
If those numbers are not there, check the following.
1. Check ESC firmware is compatible.
2. Check betaflight settings in configuration tab that bi directional Dshot is enabled
Does RPM Filtering tune my quad?
Anyone wanting to use the latest betaflight should be running RPM filtering to gain the maximum of what betaflight has to offer. It is not a substitute for spending the time to tune your quadcopter but it is a safety net to allow you to potentially push your tune slightly further if you desire.
As always any time you tune. Do some quick hover tests and check motor temps any time you changes pids or filtering settings