Betalink is a modified Betaflight firmware that adds one serial command to the MSP protocol that controls the motor velocity and retrieve the state of the FC in only one transaction. It adds a motor velocity PID on the FC that uses bidirectional DSHOT telemetry as feedback. A command line program called "betalink" is provided to test the firmware. A Simulink block is also provided within the project "RPIt" to interface the FC within Simulink thanks to a dedicated betalink block.
Check these YouTube videos for a complete tutorial on how to install and use Betalink with Simulink:
Part 1: https://youtu.be/BTN4LSLOXPI
Part 2: https://youtu.be/keIpGpJuP_k
Part 3: https://youtu.be/r3Sk5nzbywQ