Dear Forum Members,
There was a time when almost all PC's came with atleast 2 comm [ serial ] ports and USB or Firewire didn't exist but now a days the trend is changing continuously. Now a days either PC's don't have serial ports at all or have at the most one where as number of USB ports on PC's is increasing continously.

The same is the case with embedded design a few years ago most of the designs relied on use of serial RS232 ports for communication with PC's or other devices, but now a days due to USB trend more and more new embedded designs are coming with USB connectivity.

There are handfull of 8051 derivatives having USB feature builtin and even these dervatives are not accessible to all embedded developers due to their unavailibilty in local market or due to their higher costs. Since the slowest speed mode supported by USB is 1.5Mbps its not so easy to implement a USB in 8051 using software bit banging it might be possible with expensive 1 cycle DALLAS but certaily impossible with 2 cycle, 6 cycle and 12 cycle cores. There are readymade USB modules available from some vendors such as FTDI but again these are not easily available in most of the places.

I was thinking and googling for some other alternatives for implementing USB at lower cost and with easily available parts and I came across this site http://www.cesko.host.sk/IgorPlugU...32_eng.htm
This gentleman has implemented USB using an AVR certainly he has done great work.

I know this forum is blessed with very experienced embedded developers. I wanted to know have you guys tried such ideas i.e. implementing USB by software bit banging if yes how did you do it? Are there other cheap alternatives for implementing soft USB? How about using a CPLD for this purpose?

Thank you very much for reading my post.

Regards,
Prahlad Purohit