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Because I have not tested all electronic circuits mentioned on this pages, I cannot attest to their accuracy; therefore, I do not provide a warranty of any kind and cannot be held responsible in any manner.
USBTiny - ATtiny2313 based USB-to-parallel convertor
27. April 2008 - 13:02 — admin
USBtiny is a software implementation of the USB low-speed protocol for the Atmel ATtiny microcontrollers.
The software is written for an AVR clocked at 12 MHz. At this frequency, each bit on the USB bus takes 8 clock cycles, and with a lot of trickery, it is possible to decode and encode the USB waveforms by software. The USB driver needs between 1300 and 1400 bytes of flash space (excluding the optional identification strings), depending on the configuration and compiler version, and 46 bytes RAM (excluding stack space). The C interface consists of 3 to 5 functions, depending on the configuration.
The first USBtiny application author describes is a USB to SPI (Serial Programming Interface) converter. The SPI signals are connected to a female DB-25 connecter, so that the converter can be plugged onto the AVR parallel port programmer. Because the most important parallel port signals are connected to the DB-25 connecter, the same hardware (with different firmware) could be used to control other parallel port devices.