We recently added data overlay capabilities to some of our custom GoPro drop/tow cameras. We used a Pixhawk flight controller flashed with the ArduSub ROV firmware available from bluerobotics.com; this enabled us to overlay battery, pitch, roll and compass/heading data. We added a pressure sensor to the i2C port which also gave us a depth reading.
Next we used an AeroMax OSD board available from virtualpilot.co.uk, flashed with the ArduSub compatible firmware developed by Virtual Pilot. Using serial data pins on the PixHawk/AeroMax, we were able to communicate between the two devices, as well as overlay the composite video feed from a GoPro camera. Data fields on the OSD can be easily configured using the tool provided by Virtual Pilot, resulting in a clear and professional looking display. This feed can then be transmitted to the surface for viewing on any TV/monitor with AV input.
Check out the videos below showing how to flash and configure the devices, as well as the parts required and how to connect the complete system.