A lot of people are asking about how to enable Dshot Commands, which include "turtle mode" (flip over after a crash) and using your motors as a beeper. Here's the short version on how to enable it (for BLHeli and Betaflight).
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First, you need to be running a BLHeli firmware version that supports it. BLHeli_S version 16.67 or 16.63 works. If you are running BLHeli_32, you need one of the firmwares from this zip file. You need to flash either the Wraith .hex file or the Spedix .hex file depending on which one is correct for your ESC. If you are using a BLHeli_32 ESC that uses a different firmware, Dshot commands are not supported yet.
Next, you need to be using Dshot in Betaflight. If you're using Multishot or Oneshot, this won't work. The good news is that, even if your ESCs don't support Dshot600, they almost certainly do support Dshot300 or Dshot150. So you can probably use these features, you'll just give up a tiny bit of performance (or maybe you won't even notice the difference).
To use the ESC beeper, just enable a beeper mode in the Modes tab, exactly like you would if you had a regular pizeo beeper. Here's my video on how to set up Betaflight Modes.
You should know that the beeper makes your motors hot, and if you leave the beeper running for too long, you will literally melt your motors. If you're looking for your quad, beep the motors, listen for where the sound is coming from, then turn the beeper off.
To use the Turtle Mode, configure "Flip Over After Crash" mode on a switch. When you are upside down, disarm, then enable Turtle Mode, then arm. Then use the pitch and roll stick to flip yourself over.
You need to be running at least Betaflight 3.2 RC5 to make the most of Turtle Mode. Before RC5, all four motors would spin when you armed in Turtle Mode. This could result in burnt motors and ESCs if a motor was jammed with grass or dirt. In RC5, the behavior was changed to match KISS: the motors don't spin until you push the stick, and only the two motors that you command to move spin up. The other motors stay still.
Finally, in RC5 and before, you need the go to the CLI and type "set small_angle=180". Small_angle is what prevents the quad from arming unless it's flat and level. Setting small_angle to 180 disables it. Turtle mode should really override this setting, and in future RC's it will.