Hi, I need to write an application (possibly using C) to communicate with a USB High Speed Device CDC class I am developing, but unfortunately I have no development experience under Mac OS, so I am here to ask for a few help/advice. I hope I am in the right place. Since I have a working code using libusb on Linux, I have first tried to use such lib on a Mac OS without success. The device is listed correctly using ioreg -w0 -l -p but it seems to be always busy: MYUSBDEVICE@fa410000 <class IOUSBHostDevice, id 0x100001769, registered, matched, active, busy 0 (262 ms), retain 24> in fact, attempting to use libusb always results in error: LIBUSB_ERROR_NOT_FOUND libusb_bulk_transfer: Entity not found After searching a bit, I have read that it is impossible (?) to use libusb on MacOS. Then I came across these following pages: https://developer.apple.com/library/archive/documentation/DeviceDrivers/Conceptual/USBBook/USBDeviceInterfaces/USBDevInterfaces.html https://developer.apple.com/documentation/usbdriverkit I would possible avoid to write a CDC kernel driver for my application, so link #2 seems more appropriate to what I need. But isn't it available any API to develop USB CDC communications C application on MacOS ? Any suggestion is appreciated. Thanks in advance. Regards, Simon