Hello

I tried to communicate between ATMEGA32U4 (arduino micro) and carambola2 directly with USB.
Now I can speak with serial mode in python with my arduino micro. I connected the 5V of arduino with externe power supply, I use the same ground between cara2 and Arduino.
So it's good, but the carambola2 run with 3.3V and arduino with 5V. I just connected USB- and USB+ (D- D+) of arduino in the pins 20 and 21 of carambola2 without bridge.
Do you think is dangerous for carambola 2 ? I don't want break the carambola2 if I use this system in my PCB during several months.

Ronan

USB lines are different from regular digital signal lines. USB signaling has quite extensive specification and all devices that use USB must conform to those specifications independent of the device supply voltage. So if you add a level converter (which is not neccessarry, because both device use the voltages as specified in USB documentation), it is most likely that your setup will stop working. On the other hand if you connected the lines just as-is (without conforming to USB specifications), then you are somewhat lucky and you should keep in mind that it may also malfuction.

Thank you for your reply,

Between cara 2 and arduino their are juste cables but inside the arduino their are some resistances for the usb signal. I don't find more explication about usb but I think it's enough?

If your are some electrocinal ideas about composants between 1 Atemega32U4 and Carambola ?

If you are using just a regular USB cable to connect them, then all should be ok. I had the impression that you are building a custom PCB on which you are going to solder Carambola2 module and atmel chip