This blog addresses using the APM 3.x as a component in a system that is controlled by a microprocessor in place of the R/C transmitter GCS combination. The APM 3.x is a high level resource for inclusion in DIY applications. It is easilly interfaced with available microcontrollers like Arduino, PIC, MSP430 etc..

My ultimate goal is to experiment with automatic functions in Free Flight models. A Free Flight model has a fixed engine run followed by a timed glide. Historically this means launch and chase. I'm too old for that sort of thing so my initial goal is to track the glide to a minimum altitude then switch on the motor for return to launch and automatic landing. Then I'd like to experiment with automated thermal sniffing using scaled pressure from the telemetry stream.

Normally an APM 3.x is controlled by an R/C transmitter/receiver pair and communicates with a Ground Control Station over a two way telemetry link (Figure 1).

When the 3.x is used as an embedded component there is no transmitter, receiver, GCS or human interface. Instead it is communicating with other electronic components (Figure 2).

The key element here is the telemetry communication link between the microcontroller and the APM 3.x. The language used is MAVLink. It is a standard for UAV communication. Since I have no experience with this technology, I had to start from the beginning. Others may have the same problem so I am sharing the learning experience here.

Format:

The MAVLink data stream is...Continue Reading