I2C-Tiny-USB | Cheap and simple I²C to USB interface

Problem: The device seems to work fine, it is detected correctly by Linux, but i get various error messages when accessing it from the test application. Solution: First make sure that the kernel driver is not loaded when trying to use the libusb based test application. Since the kernel driver is part of the main kernel line, it may even be already installed on your system. Type rmmod i2c_tiny_usb to remove it. Also make sure that you run the test application as the root user since the standard user may lack the rights to access all aspects of the i2c_tiny_usb hardware. Problem: The device is not properly detected. Linux reports an error like "device not accepting address" in the system log. Solution: The USB interface is not working at all. Please make sure that the AVR CPU is correctly flashed and that the fuses are set correctly. Another reason may be that the zener diodes are too slow (see next problem). Problem: The device is not properly detected. Linux reports an error like "device descriptor read/all, error -71" in the system log. Solution: The device is working partly and the USB transfers are unreliable. This is often cauesed by "slow" high current zener diodes. On a previous reichelt list i had those wrong zener types. These slow diodes often seem to have thicker wires than the other parts. You can just try to remove the zener diodes and the device will work if your host PC copes with 5V on the USB data lines. Also using a USB hub between a device without zener diodes and the PC may lead to a working setup. Otherwise you need faster diodes as a replacement (reichelt no "zf 3,6" as on the current reichelt list).