AVR-CDC is an USB-RS232C interface using CDC (Communication Device Class) protocol on USB 1.1. Although CDC is a part of USB 2.0 standard, it works on low speed USB with slower speed. ATtiny45 can handle the 4800bps 8N1 well enough.No dedicated driver necessary. CDC loads Windows built-in usbser.sys.It is very low cost ith ATtiny45, this is the cheapest solution for the USB-RS232C interface.

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