I’m doing some intensive camera simulation in Gazebo and ROS and I can’t run Gazebo in real time. Do I need to modify anything with the SITL simulator to accommodate that. Does the SITL simulator use the Gazebo simulation clock or is it tied to the CPU clock? I’ve been getting a lot of these warnings:
WARN mavlink sim timeout for 10 ms
hey,
i cannot help you, but does the ros package works for you? how do you connect with mavros to px4 ros package? it starts but there is nothing following after. seems to be broken for me, maybe the mavlin instance is not started by px4 firmware. but i dont know 
[ INFO] [1458132618.198629927, 116.020000000]: MAVROS started. MY ID 1.240, TARGET ID 1.1
When i am starting SITL with gazebo like in documentation, it is working fine and i am getting a heartbeat.