Hi Janne, I'm just starting to look into this same topic, but from the other end, the software. Anyway...
For the PC ADC/DAC data interface typically you would use an ADC and DAC that has serial data I/O. I would look for a part that supports a standard serial protocol like I2C and/or SPI. You use a serial data interface because you're going to interface with USB, which is also serial. If you're not familiar with SPI and/or I2C protocols ask Google or Wikipedia. SPI is arguably simpler and faster compared with I2C, some parts support both SPI and I2C I/O. The idea of using SPI or I2C is so you don't have to deal with the drivers etc., they're standards. Plus the parts are addressable, so you can interface with the ADC and DAC via one USB port. If your ADC and/or DAC has a proprietary serial protocol, the manufacturer may be able to supply you with proprietary drivers and/or .DLL's. The serial ADC/DAC data I/O is logic level, typically 5VDC or 3.3VDC depending on your part, so you need to get this through USB to the PC. To do this you use a serial/USB converter chip like the FT2232D or FT232R from FTDI (http://www.ftdichip.com). There are others available, but FTDI is very popular amongst home-brewers, if you own something like an IW3HEV miniVNA or Prologix GPIB/USB converter to name a couple of devices then you already have an FTDI virtual COM port driver loaded on your machine. If you're using SPI or I2C, then the FT2232D is the part to use. FTDI has Windows .dll's that handle SPI and I2C (none for Linux\Unix though, but there may be some in the Community, I haven't looked). If your ADC and/or DAC use a proprietary protocol, then the FT232R part is used, it just passes the serial data through to your application via a virtual COM port which appears after you load the FTDI supplied driver. The FTDI virtual COM port drivers for the FT232R are available for both Windows and Linux. If you want to skip USB all together and use the RS-232 port, you can put the serial ADC/DAC logic-level data into RS-232 serial converter like the Maxim MAX232 part (www.maxim-ic.com). But remember, you'll need two COM ports and RS-232 tops out at 115kbps. I would venture to guess it would be difficult to get 48kHz bandwidth through an RS-232 port. What software are you planning to use in the PC? This is what I'm looking for. I'm new to this topic. Do the existing SDR software packages use a common library? Can any of them interface to a USB port directly and document the requirements? Best 73's de David WB4ONA --- In [email protected], [EMAIL PROTECTED] wrote: > > On 9 Apr 2008 at 5:03, Janne Pulkkinen wrote: > > > Hi OMs. > > > > I've tried to find info but with no greater success. I'm planning to > > build an dedicated USB AD/DA board inside my SDR TRX. Now I'm using an > > PCI sound card. > > > > I'm wondering, what is the method for carrying the data to/from AD/DA > > converters to the demodulation/modulation software? > > > > For example David, WB6DHW seem to use Cypress CY7C68013A USB > > controller. The DA/AD data is routed to this controller. What happens > > after that? Is there a software between the demod/mod software to make > > the whole thing to looks as a soundcard? Is it a complicated software? > > > > I would appreciate any info, thanks! > > > > 73 de Janne, OH1GTF > > > You have to have a USB driver, firmware for the embedded processor, and a windows > program. I haven't written software for the AD/DA board other than getting windows to talk to > the Cypress controller. The firmware for the controller and/or the USB driver needs to get the > data and format it in a format the demod/mod software needs. It possibly would be done in a > .DLL so more than one program could use it without changing the driver. Buffers need to be > designed to take care of Windows interrupt driven routines that WILL interrupt the data > gathering. It could, of course be done in Linux, which I understand is a little better than > windows for real time programs. > > Dave - WB6DHW > <http://wb6dhw.com> >
