I've taken to making external modules for my drone designs that act as watchdogs. Aka, I have an arduino on the board, along with fet based ORing for redundant 5 and 12v (3x 5v supplies, 2x 12v supplies) and temperature monitoring for major electronic items (escs mostly, but also things like video transmitters or motor cases) and voltages to far off items, (voltage feeds to the inputs of escs to see if any connections are going weird, etc etc) and other stuff. It's meant to be a safety system. Right now I use a separate 3dr radio to send the data down to the ground. This works. I like this system because not only does it remove another single point of failure (the power supply) but it lets me know if I've failed over to a redundancy. I've seen lots of drones start to become redundant, but as far as I can tell, no way of knowing when they are in that mode. If a screw fell out in the drone and is rattling around shorting out and blowing up components on a pcb, or it was raining at high altitude and water got inside, and blew up a 5v supply, but it was redundant and kept flying, normally I'd have no way of knowing this was happening, and I'd keep flying, and then that failure might move into the second or third power supply, and then I'm screwed. With this, I know something went wrong, and I can land ASAP.
I'd like to, however, for lesser systems with no ground station computer, simply send this data to the pixhawk and be able to throw up an alert that something went wrong on the minimOSD screen so you can know to come back. I don't even care if it can't say what went wrong, even just a flashing 'redundancy failure: Land immediately!' or 'system overheat: land immediately!' warning would be great!
How can I do this? I can send data through i2c or serial or anything, pwm.. I just need some way to send a status to the pixhawk and throw it up on the osd if there's a problem. Massive bonus points if I can send the actual data and do something meaningful with it, but that's not super necessary. Thank you!
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