Thanks for the quick reply.
Yes the issue was trim setting and mount RC rate parameters not set correctly.
Now I found another issue which I don’t know it’s related to gimbal or control.
I given continuous pitch and yaw but gimbal particularly stops for at least a second on both axis.
See the video here IMG_0289.MOV - Google Drive
As you mentioned the protocol is different than Mavlink and SR2 parameters doesn’t affect the system.
But SIYI manual strongly recommends that to set the SR2 parameters to sync with autopilot attitude data during flying.
Before when I connect with SBUS alone control doesn’t have this jitter issues.