All the flight controller buses: UART, SPI, I2C and CAN bus

Support my work / pawelspychalski
I am an engineer and I do flight controllers. Let me share some of my knowledge with you. Today let's talk about which buses modern flight controllers like Betaflight, Ardupilot, and INAV use. Pros and cons of each one and what kind of devices we connect to every one of them: UART, SPI, I2C and CAN bus!
0:00 I'm an engineer
0:31 Flight Controller connected devices
1:10 Buses: UART, SPI, I2C, and CAN
1:33 UART aka Serial port
4:36 SPI bus
8:29 I2C bus
10:38 CAN bus
11:40 Happy flying
#fpvuniversity #betaflight #inav

[@M0rdH0rst]

Thanks for the refreshing 😉 The CAN-bus is very popular in cars and what I have seen of it, has some overhead, to meet the safety standards. The SPI bus also can take more than one device, but then it needs an extra port for CS (chip select). Useful for sensor data from external ADCs and for flash memory.

[@Idefix70]

Thanks for this explanation. Working on my first iNav setup, this is of great help!

[@srul76]

As always great video many thanks Pavel

[@WSNFPV]

It will be nice to see details of this protocols to understand it limitations and adventages.

[@blemysh0]

Great explanation Pawel. Greetings from MX 🇲🇽

[@underlecht]

great video. lots of new info. half-duplex, full-duplex - did not hear about those.

[@carlosah2598]

Thank you Pawel for your clear explanation as always. It means that our fligh controllers could use Can bus in the future with Inav "5.0"....👌

[@FPVUniversity]

I hope so!

[@SyvaPankumi]

Дякую 😁

[@MCsCreations]

Awesome, Pawel! 😃 Thanks for the lesson! Stay safe there with your family! 🖖😊

[@calisti9308]

I wish I would have found this video earlier! Thank you!

[@FPVUniversity]

Glad that you like it

[@TNCS8884]

Thank you very much.

[@FPVUniversity]

My pleasure

[@carnagefpv8256]

Since you mentioned CAN, is there any future hope for CAN support in INAV? I've been looking and it seems like CAN has become very useful on ardupilot, perhaps we could benefit?

[@michaelosumune2149]

I want to connect multiple voltage and current sensors while controlling an ON and OFF switch using the Jetson nano using the UART but I want to know the best alternative to do this such as CAN etc. This device want to industrially customize. Kindly need your advice . Thank you

[@embededfabrication4482]

is there CAN on a matek f765 wing ? is there a way to connect RTK gps to such a FC?

[@kelvindeen]

How would you go about with communicating to a FC via an UART serial pin/port? I cant figure out for the life of me how I can use any protocol to do this. I dont understand how CRSF protocol (used by ELRS) communicates to the FC all the stick inputs with all the different channels. Do you use normal PWM values but in serial code?or a value just between 1000 and 2000? I am talking about FC that run Betaflight. Could you help me out here for a promising project I am working on? I am currently using Arduino IDE with esp32 with UART pins. Would be awesome to get your 2 cents on this. Thanks and I appreciate your content!

[@stevefox3763]

i2c is very handy, i have 6 devices connected on one build, soon to be 7 or 8.

[@FPVUniversity]

I2C is also very slow comparing to other buses and it gets slower the more devices you connect to it

[@febbyeka]

Hi, are there any hardware or software additional setting to use multiple i2c devices into a single i2c bus in the flight controller?

[@FPVUniversity]

@@febbyeka multiple devices on I2C work out of the box. No extra settings needed

[@pgabrieli]

thank you very much. I'm a newbie, could you please explain why "SPI" onboard receivers are always worse than external receivers on UART? does it have to do with the interface (SPI/UART)? thanks again

[@FPVinPA]

I second this question.

[@olafschermann1592]

It has nothing to do with the connection protocol (SPI vs serial). Often the implementation is executed very poorly especially the antenna which is just a wire. There are well implemented SPI receivers like the new ExpressLRS onboard reiceivers on tiny whoop boards.

[@pgabrieli]

@@olafschermann1592 but SPI *is* a serial, right?

[@olafschermann1592]

Yes, both are serial protocols. UART is 1 sender 1 receiver, is asynchronous, has built in parity and handshaking uses 2 wires. SPI can have multiple partners = is a bus, uses 4 wires, is synchronous and needs a clock wire, has no handshaking, parity or errorcorrection, is faster, is simpler, is smaller.

[@pgabrieli]

@@olafschermann1592 thanks!

[@jeremygalloway1348]

What type of engineering? Radio? Aeronautical?

[@hemanthkrishna5343]

I wanted to add compass and baro to my FC but it only has one i2c bus. Is there any way to remap a UART or any other pads?

[@FPVUniversity]

You can connect multiple devices to a single I2C bus

[@hemanthkrishna5343]

@@FPVUniversity Wow! I spent the better half of the day researching this. Thanks for the reply. Hope it does not affect the performance compared to an FC with integrated baro

[@FPVUniversity]

@@hemanthkrishna5343 majority of FC have baro wired internally to I2C as well. And very often the same I2C bus as external one

[@jimmytheriot8978]

Can you help , I have the F405 wing set up on I nav , when I arm the motor and put the plane in stabilize mode and move the ailerons to full deflection and let go of the stick they don't return to center but if I disarm they go back to center and function normal when the plane is disarmed, it only happens when I arm the motor

[@carnagefpv8256]

Sounds like stabilize mode is just doing it's job. The pid controller will "wind up" when it's trying to make changes, but not seeing results. This is why the control surfaces stay deflected. Disarming either disables or resets this process(can't remember).

[@jimmytheriot8978]

@@carnagefpv8256 It's weird cause I never had that happen before, I always test everything on the ground before I fly And never noticed that till now , And the last time I flew when I made a turn I added rudder And the alirons straightened back out But it seemed like the rudder stayed stuck Because it kept crabbing to that Side

[@jimmytheriot8978]

@@carnagefpv8256 Appreciate the input, by the way check out my homemade cockpit let me know what you think

[@carnagefpv8256]

Which INAV are you using? Do you have turn assist on? If so, turn it off. On builds previous to 3.0 yaw stabilization is not properly functional, so use RC yaw in the mixer, not stabilized. This is all previous to 3.0 if post 3.0, I'm not sure then.

[@carnagefpv8256]

@@jimmytheriot8978 could also be a bad servo/ analog servo midpoint drift/bad linkage geometry/binding/loose connection. I don't know your setup but that's where I'd start

[@necipali1795]

Hi, i have been watching your videos, mostly about gps. What i would like to ask you, i have m8q gps with barometre and magnetometer, so there are 6 wires on it, but i don’t know which wire goes where on my Cinebot30 drone’s fc, can you explane me like explaning to a newbee, cause this is my first drone that i haven’t fly yet. Thanks 🙏🏼

[@FPVUniversity]

I2C for mag and baro will be marked as SCL/SDA , DA/CL, D/C or something like that

[@necipali1795]

@@FPVUniversity thanks for the answer, yes on gps there is SDA and SCL but on fc there isn’t. So where should i solder this sda and scl wires to fc?