Hi Igor, > May someone tell me how to program Atmega through usb using FDTI?
Not exactly an OpenBSD related question, but the easiest way is to burn a serial bootloader (e.g. the Arduino bootloader) onto the AVR and use avrdude in serial mode to upload your firmware. FTDI bitbang also works, but is more complicated, I would not recommed it. Contact me privately if you need more detailed help. Daniel