Open Protocol and Data Transparant Transmission on M210 and M600

Hi,

The following page

https://developer.dji.com/onboard-sdk/documentation/Protocol-Documents/main.html

indicates that the Open Protocol and Data Transparent Transmission are not available for the M210 and M600. Is this true? Are there alternatives for these drones?

I would need these features to send custom data and commands between the Mobile SDK and the Onboard SDK.

Best regards,

Bart