I could finally get my px4 firmware to stay armed in offboard mode by porting the CPP example from the documentation to python. (Previous problems see http://discuss.px4.io/t/px4-ros-node-communication-setup-for-rovers/368 for reference - in short: I am trying to control a rover frame with a pixhawk running px4 via ROS messages that are sent via Mavlink. Using https://pixhawk.org/dev/ros/ground_rover as a base.). That means that I now have a solid blue main LED when executing my code.
Next problem seems to be that my SERVO_OUTPUT_RAW (monitored by QGroundcontrol) always stays on 1500 for all channels even though i am sending messages @10hz on /mavros/actuator_controls with +1 and/or -1 for all channels (which should be the max/min as far as i understand). Sending RC
Users on Gitter said that this problem could be resolved by changes to the /etc/extras.txt but are not more concrete. also https://pixhawk.org/dev/ros/ground_rover says that the standard stream should work fine as well.
The code snipped I am using is
publisher_actuator_control = rospy.Publisher('/mavros/actuator_controls', ActuatorControl, queue_size=1000)
rate = rospy.Rate(10) # 10hz
testvalue = 1.0
while not rospy.is_shutdown():
# 8x testvalue for 8 channels
acm_controls = [testvalue, testvalue, testvalue, testvalue, testvalue, testvalue, testvalue, testvalue]
# group mix = 0 => flight mixer
# 3 => manual control
# neiter 0 nor 3 does work
acm = ActuatorControl(controls=acm_controls, group_mix=3)
rospy.logdebug("result of act update: " + str(publisher_actuator_control.publish(acm)))
# result of the publish method is always None
What is curious is that sending RC override messages such as
rc_msg = mavros_msgs.msg.OverrideRCIn()
rc_msg.channels = 2000
pub = rospy.Publisher('/mavros/rc/override', mavros_msgs.msg.OverrideRCIn, queue_size=10)
Does create some new entries in Qgroundcontrols Mavlink Monitor, that also contain the values being sent to the topic. However, SERVO_OUTPUT_RAW still does not care about the changes at all.
Now my question is: what am I doing wrong? Is there some feature in the PX4 firmware that I need to enable/disable in order to get the values through? (Note that my ESCs are disconnected for testing - does this make any difference?)
Any help is highly appreaciated!