Dronekit exception sending messages to system IDs > 127

[seanmcleod]

When we connect the Tower application to a Pixhawk which also has APM Planner 2 connected we see an exception in the Tower application in a call to:

packet.payload.putUnsignedByte(target_system);

The issue is that the system ID of APM Planner 2 is 252 and the dronekit-android throws an exception since it sees the target_system as -4 which fails the following check in putUnsignedByte() when trying to send a message to APM Planner:

if(data < UNSIGNED_BYTE_MIN_VALUE || data > UNSIGNED_BYTE_MAX_VALUE){ throw new IllegalArgumentException("Value is outside of the range of an unsigned byte: " + data); }

Presumably there shouldn't be a limit in dronekit preventing it from sending Mavlink messages to system IDs > 127?

Regards

[seanmcleod]

Is Tower/dronekit-android known to work well with more than 2 systems on a MAVLink network? Or has it only been used and tested on MAVLink systems with 1 vehicle system and Tower as the only ground control station?

The reason I ask is that in addition to noticing the issue with dronekit-android throwing an exception when trying to send a MAVLink message to a system with a SystemID > 127 we are seeing other issues like Tower connecting and disconnecting constantly and changing modes when we have 3 systems on the MavLink network.

In this case instead of APM Planner we have our own system, a Raspberry PI using dronekit-python connected to a MavLink network with a Pixhawk and Tower.

When we came across the exception issue with SystemIDs > 127 we changed the default SystemID that our Pi system was using which was 255 to 20, but then although we don't see Tower crashing/throwing an exception we see these other connection/mode issues.