search

Carbon225 / raspberry-sbus

Linux/Raspberry Pi SBUS driver
MIT License
34 stars 10 forks source link

How to do the connection from Rasberry Pi 4 to sbus? #10

Closed research-boy closed 7 months ago

research-boy commented 3 years ago

@Carbon225 I am new to this , might feel like a silly question :). This is what i understood, connect the sbus tx to the Rasbeery Pi 4 GPIO14 . Is there any need to use inverter in between the above two ? What i am trying to do is to control blackmagic studio camera settings through sbus , which i need to send control signals to appropriate channels in the sbus. Will be a great help if you can guide me how to test it out with what you have made. Thanks

Carbon225 commented 3 years ago

If you want to test the library connect RX to TX (gpio 14 to 15) and run the send_to_self example. Most drones use active high signals that's why I mention using an inverter but I don't know about cameras. That's actually quite awesome as I never imagined cameras had SBUS.

Carbon225 commented 3 years ago

Just to clarify, you're supposed to connect gpio 14 which is TX to the RX pin on the camera. Also do the raspberry pi setup from the readme (device tree overlays) to activate that UART.

research-boy commented 3 years ago

@Carbon225 Thanks for quick replay, how normally people use is use a futaba remote to send data to this, which works fine. What i want know is whether it is sending the same signal as a futaba ?

Carbon225 commented 3 years ago

It works for sending just fine. It will send an active low signal which is normal for UART. So for a drone you would need an inverter.

research-boy commented 3 years ago

Thanks, will update you

research-boy commented 3 years ago

@Carbon225 Hi , I would like to know is there any way i can invert the signal in the code itself

Carbon225 commented 3 years ago

I have not implemented that. I think it might be possible with certain adapters but I do not know much about it. If you know how to invert the signal in software please let me know, I will add it. I do not think many adapters support this feature though.

Carbon225 commented 3 years ago

Right now I'm working on the v2.1 version and I have a fully functional setup on a breadboard so I can give you schematics.

research-boy commented 3 years ago

@Carbon225 cool , will be great if u can share ASAP , About inverting , this is something i found : https://github.com/Cleric-K/vJoySerialFeeder/blob/master/Arduino/Sbus_invert/Sbus_invert.ino https://github.com/Cleric-K/vJoySerialFeeder/blob/master/Docs/Sbus.md

Carbon225 commented 3 years ago

I had this in the readme: https://electronicspost.com/wp-content/uploads/2015/11/Transistor-as-an-inverter.png I have a level converter as well to boost the signal to 5V but I guess your camera might not need that. And even most 5V electronics work with 3.3V signals.

Carbon225 commented 3 years ago

20210805_154857.jpg This is exactly what I have right now. Additionally I have that level converter right after the raspberry TX pin.

Carbon225 commented 3 years ago

This kind of level converter: https://www.sparkfun.com/products/12009 Though like I said it might not be necessary.

Carbon225 commented 3 years ago

Those links you sent are for an arduino inverter I think. It's quite cute. I don't know if that's what you wanted (a seperate device to work as an inverter) or if you wanted software to invert the signal directly on the sender. I think it was the latter.

research-boy commented 3 years ago

I think you can use IC74HC04 for inverting, i am also not sure about the Arduino code i shared.

Carbon225 commented 3 years ago

This is a quote from that repo: SBUS protocol sends data over a UART pin configured at 100 000 bps and using 8-E-2 framing. It also uses inverted signal levels. This makes it impossible for most USB UART converters to read the signal directly - the signal must first be inverted. So like I thought most adapters cannot invert the signal. Even most microcontrollers don't have that feature. The ESP32 can do it I think. But this library is for computers so I'd want it to be as compatible as possible.

Carbon225 commented 3 years ago

I do not know that IC but I guess there might be inverters like that. If you're designing a PCB you might want to use it. But really a single transistor is all you need.

Carbon225 commented 3 years ago

I don't know if you've ever done any kind of electronics projects (I mean with some analog stuff and the like) so I understand if you're afraid of it. If you're careful it shouldn't be a problem.

research-boy commented 3 years ago

@Carbon225 I understand to read will need inverter , but to write it didn't make sense. :)

Carbon225 commented 3 years ago

Do you know if your camera needs an active high signal (inverted)? Like in a drone.

research-boy commented 3 years ago

@Carbon225 i couldn't find anything in the documents , but i tried using a futaba transmitter and reciever , which worked. The reciever i have is https://futabausa.com/wp-content/uploads/2018/09/R2008SB.pdf If you want know about the camera control : https://documents.blackmagicdesign.com/DeveloperManuals/BlackmagicCameraControl.pdf?_v=1539929000000 Hope this will be helpful.

Carbon225 commented 3 years ago

So yes it seems you will need an inverter for TX. I don't have any send-only examples but really it's just the sbus.write() function and you can adapt the send_to_self example. You can make a loop that sends a packet every 10ms which is similar to real hobby receivers like your futaba. Make sure to use a delay. Any faster and your camera most likely won't recognize the packets. I'm quite interested how you manage because it's such an original application.