The Nybble option on the app works for bittle as well unless there is a specific option for bittle now. I got all the commands to work with the bluetooth adapter other than Turbo, since I think that is nybble specific.
In the customized robot option if then APP, you can add more buttons. The command for Turbo is 'g'. You can test it on the serial monitor then assign a button in the app.
We now have a newer app for Bittle. But you will need to upgrade the firmware.
https://docs.petoi.com/upload-firmware
https://docs.petoi.com/mobile-app/introduction
The Nybble option on the app works for bittle as well unless there is a specific option for bittle now. I got all the commands to work with the bluetooth adapter other than Turbo, since I think that is nybble specific.
http://www.codeandrobots.com/