Why must we figure out Protocols? Another Way?

As I was looking at all this programing and flashing going on in the RC community with ESCs Bootloaders / Oneshot , BLHeli and simonk firmware, a question has occurred to me. I understand there are several RF chips that each manufacturer uses, CYRF6936, NRF24L01, A7105 and CC2500 for example and therefore must have some base protocol for each type of chip. Is it possible to load or flash the receiver with what ever protocol you wanted as long as it was compatible with the RF TX? Somehow the original protocol is flashed to the receiver. What if it was re-flashed with something we already know instead of trying to reverse engineer every new model. I get that it may be another challenge figuring out how to re-flash every other model so I'm just curious if that is even possible. After that, I think it would be cool to try to re-flash a receiver.

I actual figure there's a good reason why not but I'm not privy to that answer.

Thank you!

Well, you can build your own receivers. That's been done.

But if that's not what you want, you have to figure out what to flash. There are at least three different places that could be controlling the protocol, and I think only one of them is reasonable for installing deviation protocols.

One is that the flight control cpu does the protocol. That handles all the sensors and controls the motors as well doing the protocol. If you reflash that, you have to update not only the protocol, but all the flight control firmware as well. There is open source flight control firmware available, and some of the proprietary boards have been reflashed with those, but doing that really makes it a different aircraft. You're probably better off replacing the flight control board with one designed for this, and reusing the frame and motor electronics.

The next one is if you have a separate CPU talking to the RF module, typically on a daughter board. That one just controls the protocol, and is the one that would work best with deviation source once you've hacked the circuit to let you flash the board.

Finally, you may have an RF chip that has on on-board mcu. I'm not really familiar with those, because we can't reverse the protocol on them. While you could reflash them, your have to figure out the internal protocol used between the mcu and the RF chip. That may or may not be documented, and figuring it out is probably no easier than reversing a protocol for deviation.

But really, this is only an issue if you want to pilot cheap toy grade craft. If you're willing to pay for hobby grade craft, they either use a well-known protocol, or are available in a form that lets you plug in your choice of receiver. There are some protocols we'd like to have to use their receivers to get some advanced features, but that doesn't stop us from using any specific aircraft. And at some point, I expect the open source receivers to grow those features.

That all makes sense. I suppose it's typical that the small Quads can't be upgraded to a standard RX like DEVO or DSMX RX. I just realized a lot of the protocol work is for the smaller cheaper models. A lot of the RC planes, quads and Heli's you can simply put in your RX of choice. I realize that it must be a lot of work to get a protocol developed for a $20 quad that comes with a remote already.

The path of least resistance is the best I suppose. I ordered a logic analyzer to do SPI Captures to start understanding the process. I don't know if I'll be able to ever create a protocol though since reading about that part it seems I won't have the programming skills to get that far. Hopefully I can post Captures and get some help there. All this was sparked by a cool little "Cheer X1" quad I got at Christmas time as a gift. I would like to us my DEVO10 but haven't seen any development on it yet so I thought I'd start with this one myself.

Thanks for the explanation! I'm looking forward to some good captures and hopefully they're not too complex to at least show if it is similar to something out there already.

Any pointers will be much appreciated. For the most part, it's a new challenge I'd like to take on. I don't think this small quad is worth all the effort but the challenge is part of me liking this hobby.

Thank you,

Jasenk wrote: All this was sparked by a cool little "Cheer X1" quad I got at Christmas time as a gift. I would like to us my DEVO10 but haven't seen any development on it yet so I thought I'd start with this one myself.

That may be a harder target as the Cheer X1 quad itself (or at least the one I saw) uses a combined chip from NST as both the 2.4 GHz radio and the MCU of the flight computer. There is a part number (can't find where I wrote it down at present) but little to be found in researching that.

The transmitter on the other hand seems to use a distinct LT8910 radio and MCU, so you may have luck sniffing the connections between. A Chinese language data sheet for the LT8910 radio IC is "somewhat available" at www.nst-ic.com/f/1/1311114648.pdf (try an offline download, it is very slow) but I didn't really look into it in detail to see if it is compatible with anything else.

If you want something of that size and style the similar looking little Hubsan (better known in Estes livery) has both a supported A7105-based protocol and a community of people reflashing the onboard ARM MCU.