Problem with calibirating ESCs

[supriosamanta]

Hi, great project. I am currently implementing this using a begalbone black, mounted with a cape. I have followed the instructions provided on the BBBmini github page to download, configure and build the kernel and also the arducopter firmware. I am using the 4.0.6 version. My ESCs are from readytosky 30A (https://robu.in/product/readytosky-30a-2-6s-esc/) used with a 3s lipo. Here is the problem I am facing, on calibirating the ESCs manually, using my sbus based receiver, I achieve a consistent speed of 5000rpm on all my motors when the transmitter throttle is set to 50%. My motors can spin upto 10000 rpm. When the ESCs are plugged back to the begalbone black cape, following the diagram on the github page, the motors spin with different rpms. The difference in the RPM is usually around 2000-3000, sometimes more than 4000 rpm. Can you point out potential issues that can be causing this? My calibration sequence is the one mentioned in the ardupilot website. I have tried manual, all at once and semi automatic sequence but nothing seems to solve the problem.