Greetings. Attached is very early, "proof of concept" alpha firmware to test tone output signalling for the Pixhawk LITE via the AUX pins (since this board does not have a Speaker/Buzzer OUT pin).
PLEASE NOTE THE FOLLOWING! (As the saying goes, not the usual yadda yadda!)
No warranties, expressed or implied. Install this firmware at your own risk! (It works fine for me, but that doesn't prove anything!)
This firmware is based on 3.4-dev. Whether or not you actually want to fly with it is up to you.
This firmware is currently hard-wired to output on AUX pin 1. If you have anything else on there, be sure to remove it. Later versions should allow you to choose any AUX pin.
This current firmware is designed for a PASSIVE piezo transducer. If you try use an ACTIVE piezo (the type that generates its own tone) you'll likely just get a continuous buzz. Later versions should be able to support active piezos at least for basic signalling purposes.
With a passive piezo, this firmware will play a short tune when the board starts up. Right now that's all it does as far as the piezo is concerned, and don't expect Mozart! More to come.
You can connect a passive piezo directly to AUX pin 1 between GND and SIGNAL, but (a) it will be very low volume, and (b) this can stress the output circuitry of the processor and board. I STRONGLY recommend attaching a passive piezo via a resistor and NPN transistor driver in a standard configuration. A voltage like +12v to the transistor should also provide significantly louder output from the piezo.
Please let me know if you have any questions. Have fun!