Replacing SHIFTOUT with USB - off the BS2 coding subject!!

vaclav_sal

This is off the subject of BS2 coding.
I have partially finished my BS2 project of interfacing the DDS (direct digital synthesis) oscillator to SDR (software defined radio). Since the main (audio) processing is done by PC audio card I am looking into replacing the BS2 controller. It is now setting the DDS oscillator via SHIFTOUT.
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I need to build / find a device which would interface via USB. Ideally directly - no serial to USB conversion. However, I do have commercial USB to serial interface working with my other radio and may use that for starters. But I really need to replicate the SHIFTOUT software in hardware.
Any constructive comments on this would be appreciated.
Thanks for reading.
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Mike Green

The only way you are realistically going to do this is to have some kind of microcontroller. In any event, you will need some kind of custom driver on the PC side. You may be able to find a commercial USB / SPI type of adapter that could be made to work, but it will be expensive and it will still need some customization on the PC side. There are microcontrollers on the market with built-in USB interfaces and you may possibly find some sample code that's close enough to what you want to be able to modify it for your use. Again, you'll need some kind of custom driver for the PC side. In any event, you'll have to do your own searching for these. Microchip makes some. Dallas/Maxim I think makes some and there are plenty of others.

If you really want to provide a hardware-only interface, you might start with the FTDI USB to parallel FIFO chips. These look like a serial port to the PC, but present the data in 8-bit parallel form with some handshaking lines. You could use a 555 timer to produce the clock output and a parallel to serial shift register (74HC165?) to shift out the data. You'd need a counter and some sequencing logic to start things when data shows up and stop things when the data's been shifted out.