Cleric-K
commented
6 years ago Hi,
for IBUS the solution already exists: https://github.com/wdcossey/flysky-ibus-leonardo.
The problem with SBUS is that it uses inverted voltage levels which is a problem in Arduino, because the hardware serial port of the Atmega microcontrollers does not support inverted signals. And software based serial port is simply not fast enough to read the 100 000 bps bitrate of SBUS.
Theoretically speaking, what you say (combining the software inverter (SBUS_invert.ino) with the HID part) is possible, but practically it won't work. The reason is that even for such a simple action as reading a pin and writing the inverted value to another (this is what SBUS_invert does) it takes as much CPU as it cat get and even optimizations were needed - otherwise it was not fast enough and it misses incoming bits. When the remaining code for the HID and serial is added it will simply not let the soft inverter run fast enough.
That's why the first example you sent requires Teensy. If you look at line 14 you'll see:
SBUSSERIAL.begin(100000, SERIAL_8E1_RXINV);Pay attention to RXINV part, this is what tells that the port uses inverted signal on the receive pin. The ARM microcontroller of the Teensy supports this inversion in hardware. That's why it is no problem to do it.
So for Arduino there are two options
- make hardware inverter - for example https://imgur.com/a/dDPaZ.
- use the UNinverted output of the receiver if one is available. Look at https://oscarliang.com/uninverted-sbus-smart-port-frsky-receivers/ (this is what is used on the second link you sent me)
In both cases some extra work is required but the code of the second link should work.
Radrik5
Maybe it's not the right place to ask but it seems you know a lot in the field.
I wonder if it's possible to flash an Arduino board with something that takes IBUS/SBUS signal from the receiver and converts it into USB HID Joystick. So you could just plug it in and run the simulator. There is the Joystick library for Arduino and you have the Sbus_invert.ino sketch. If only we could combine them together :)
Is it theoretically possible or there are some hardware limitations or something? The demand for such board seems to be pretty high (it's a much better replacement for audio-usb converters) but I have found only two not very popular examples: one, two (in Russian).