Hi David! > 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.
Thanks David, I will definitely do some studying about those, especially about SPI! > 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. Nice! So I should probably search for ADC/DAC pair that are supported by the manufacturer. Man, this would ease the work really much! > 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. > Well, you guessed it right :) I have MiniVNA. I think you brought up an very important thing here: The FTDI and virtual COM - one interesting thing more to study! > 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. I didn't realize that I could carry the IQ stream through an virtual com. I'm just wondering if the software I'm using could receiver data from such address (KGKSDR). > 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. Ok, well yeah, I will stick with the USB idea. COM ports are really slow and would definitely limit the BW of the IQ stream :) > 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 Well, I have been using KGKSDR with my homebrew HF TRX. I would really love to use dedicated ADC/DAC card and have it inside the TRX instead of using my PCI card. At least WinPSK and MultiPSK are supported and I think (not sure about this) but the audio is somehow fed through an DLL, because the audio is not routed through any virtual cables etc. Of course the DLL will also control the PTT function. I haven't found any documentation concerning the KGKSDR's DLLs. I'll do some more search if I'll find anything. Many thanks, de Janne, OH1GTF ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ
