This is a simple design that interfaces a PIC 16F877 microcontroller to the USB bus using the FTDI FT245 USB FIFO device. It has been designed using a simple single sided PCB with only one surface mount device, the USB chip itself.
The design uses the FTDI FT245BM USB FIFO device. This part handles all the details of communicating via the USB bus, all it needs is a simple, 1KBit serial EEPROM to hold some USB configuration information and you are ready to go.
The FT245 has the following interface to the microcontroller.
D0 to D7 comprise the 8 bit data bus interface, in this design it connects to PORT D of the PIC micro controller.
RD# and WR are the Read and Write pins of the device, they connect totwo output pins on PORT C of the PIC microcontroller Both signals are active low.
Finally, RXF# is the RX FIFO flag, when logic 0, it indicates there is data to be read from the device. TXE is used to indicate that it is possible to write to the FIFO device, logic 0 indicates it is OK to write data. Both of these signals connect to input pins of PORT C of the PIC microcontroller.
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