Need help with ESCs

[adithyay328]

1: Hey, guys! So, I need some help with understanding ESCs. So, I'm building a custom drone based off of a BeagleBoard paired to my PC via XBEE(not the problem). Now, I'm connecting the ESC up to my BeagleBoard, which should work fine electrically, and I already understand the protocol in use(SBUS). Now, my question is, how would I know what data to send over the protocol to achieved a given result.

 

For example, let's say I want to send 50% power clockwise through the ESC. What data would I need to send over SBUS to get that result?  

 

2: I need to send control signals to an SBUS compatible gimbal controller(3 axes). What signals would I need to send over to control each axis, and how would I separate the different values(different signals for each motor)?

 

Thank you so much for helping me!

Parts involved:

ESC: https://hobbyking.com/en_us/hobbyking-60a-blueseries-brushless-speed-controller.html

Motors: https://hobbyking.com/en_us/turnigy-aerodrive-sk3-5045-450kv-brushless-outrunner-motor.html

Gimbal Controller: https://hobbyking.com/en_us/storm-32-3-axis-brushless-gimbal-controller.html

Gimbal Construct: https://hobbyking.com/en_us/hobbyking-brushless-actioncam-gimbal-with-2208-motors-and-3k-carbon-construction.html

Control board(source of signals and is receiver of user input): https://beagleboard.org/green

[Hackentosher]

For the love of God, there are purpose built flight controllers designed to accept and interpret an inverted sbus signal. The problem is sbus is a protocol that carry 16 channels over one wire, so you'd have to figure out the exact square wave for every value on each channel. It's just not realistic. Please spend the $20 and get something like a Hyperlite f4, a board designed for this use case. 

[adithyay328]

3 hours ago, Hackentosher said:

For the love of God, there are purpose built flight controllers designed to accept and interpret an inverted sbus signal. The problem is sbus is a protocol that carry 16 channels over one wire, so you'd have to figure out the exact square wave for every value on each channel. It's just not realistic. Please spend the $20 and get something like a Hyperlite f4, a board designed for this use case. 

I don't think you understand that this is an educational project. I  was just wondering if thee was a way to ID the signals other than intercept traffic from a transmitter. Thanks for your response, but could you at least point me in the right direction to find the info? Or would I need to contact someone involved in the making of these devices? Thanks!

[Hackentosher]

2 hours ago, adithyay328 said:

I don't think you understand that this is an educational project. I  was just wondering if thee was a way to ID the signals other than intercept traffic from a transmitter. Thanks for your response, but could you at least point me in the right direction to find the info? Or would I need to contact someone involved in the making of these devices? Thanks!

The sbus protocol and signal are receiver side, you'd need an oscilloscope connected to the sbus signal pin of a receiver. Sbus is a protocol designed by futaba, originally designed to reduce the number of cables running everywhere on a large model. This was achieved by running one 3 pin cable to (for example) the tail of a large gas plane to a breakout board where the servos could be connected. To achieve this, you have to encode the data for the channels into a serial packet and send it over the signal wire. I'm sure Futaba spent a lot of R&D on this protocol, but a lot of other companies such as fr-sky have implemented it into their receivers so it might be open source. Idk, look it up. 

 

If you want to learn more about flight control firmware, look at the Betaflight source code. 

[adithyay328]

Thanks for the in depth awnser! Luckily, I was able to find the source code developed by Futaba before I posted this question. You did provide a solution to my problem, but I was already considering intercepting the signals with a soc connected to the receiver. I was just wondering if you knew of any  ESC signal to motor rotation speed tables or graphs. Thanks for the suggestion though. The reason I asked for the graph was because the people making the ESCs would need something for reference, such as a table or graph. 

[adithyay328]

OMG, I AM SO FREAKING STUPID LOL. The functionality I was looking for was the ability to calibrate the ESC(which every ESC can do). GOD HELP ME. Bruh I'm so stupid! Thanks for the assistance though, absolutely invaluable, @Hackentosher