mavlink/qgroundcontrol — Issue #29: QGC shouldn't double-transmit every message
Author: Susurrus
Created: 2012-02-08 01:32:42+00:00
State: open

From looking at the messages that my microcontroller receives I see that QGC double-transmits many of the messages it sends. On a fast link that causes problems with state machines if they've already transitioned. For example, with both the PARAM_REQUEST_LIST and MISSION_REQUEST_LIST after I receive the first message I respond and move on, but I'll receive a second transmission from QGC. This double-transmission isn't a big deal here, but it is once we move into the mission protocol where QGC has to request missions and it does it twice. According to the documentation an error should be thrown if a request comes in out of order, which the second request will always do. This also reveals how underspecified the parameter and mission protocols are when it comes to exception handling.