AD9850 DDS

Sun Mar 17 09:21:00 CDT 2013

Is the Si570 still available?  Updated part?

More on DDS vs Si570 <http://www.hanssummers.com/ddssi570.html>

Useful Analog Deveices DDS
tool<http://designtools.analog.com/dtDDSWeb/dtDDSMain.aspx>

Martin

On Sun, Mar 17, 2013 at 8:30 AM, <wb4jfi at knology.net> wrote:

>   If you just apply power, you will see an RF signal out of the DDS (make
> sure any “sleep” hardware pin is OFF – not in sleep mode), but the
> frequency may not always be the same.  I think that it does default to
> certain values, but don’t remember with the 9850.  The AD9850 data sheet
> should tell you what the default power-up values are for the various
> parameters.  If I remember correctly, there is also a hardware line that
> must be either high or low to select serial-loading of data.
>
> There are also more bits than just the FTW that must be loaded into the
> AD9850 each time.  I will look at the data sheet again, I suggest that you
> become rather familiar with the data sheet.  I think there are like 40-bits
> that must be loaded each time, with 32(?) being the FTW.
>
> The FTW calculations are generally the same for all Analog Devices DDS
> chips.  First, you divide the number of bits in the FTW (2^32, or 4
> billion-something) by the master oscillator frequency (in Hertz), which
> yields the number of Hertz per bit (or sub-Hertz per bit actually).  You
> then multiply that number by the frequency that you want generated.  The
> 32-bit word result is the FTW that must be sent to the DDS chip.  Add that
> to whatever other bits are necessary, and then crank all those bits out one
> at a time, while toggling the clock line.  I can’t seem to find my AD9850
> data sheet at the moment, and must head back to bed after feeding the
> cats....  more later.  (the above is from memory)  Read carefully the data
> sheet, especially regarding phase of clock versus data bit transitions,
> especially at the end of the writing process.
> Terry
>
>
>
>  *From:* Alex Fraser <beatnic at comcast.net>
> *Sent:* Sunday, March 17, 2013 3:32 AM
> *To:* tacos at amrad.org
> *Subject:* Re: AD9850 DDS
>
>     Yes Terry it does help.  I have been searching the web off and on all
> day.  I found some good stuff which I will regurgitate here when I can
> organize it.   I think tomorrow I'm going to put some power on one of these
> boards, not that I expect to get a wave out, but to see what physically I
> must do, get power to the bread board, cut jumpers and what not.  I am
> starting pretty much from scratch, I haven't bread boarded in years.  I
> might as well burn my first one up and get that behind me ;-)  We must
> sacrifice and see the smoke!
>
>     It seems to me that I had a two meter radio years ago, an Icom 22s
> IIRC that used diodes soldered on a board to set the channels so if you
> wanted to change frequency you pulled the board. looked up or calculated
> the placement of diodes and saved yourself having to buy a crystal.  I
> wonder if it would be that simple for getting one particular frequency
> using the parallel input?  I have to do some reading on what this chip
> needs to see to put out.
>
>     As I said I'm starting pretty much from scratch.  I have a frequency
> counter kit I will build this week and it will give me a chance to play
> with my new soldering iron.  I'll start mail ordering other stuff too, I
> need a stock of headers and stuff like that as these data based soldering
> projects don't lend them self to dead bug methods easily. I'll also
> probably get an Arduino board and proto shield as I found a couple of pages
> showing how to's for these boards.  As you know you have to think down the
> road with projects if you don't want to be waiting at the mailbox for parts.
>
>     I do have a couple of laptops with parallel ports and just the other
> day I found my stash of gold plated d25 connectors.
>
> wb4jfi at knology.net wrote:
>
>  Hey Alex.
> The AD9850 is pretty old as far as DDS chips go.  I was playing with them
> and the AD9832 several years ago.  I have not used this exact module, but
> have one that I purchased recently that is very similar.  I also have
> several different ones that I home-made using the AD9850, AD9851, AD9832,
> AD9835 over the years.  Plus, we have used the David Brainerd DDS boards
> that use the newer AD995x series DDS chips.  The newer chips use less
> current and produce fewer spurs, as the A/D uses more bits – generally
> speaking.
>
> We used to drive these DDS chips with a parallel port on a computer, using
> a few bits to drive the DDS chips in SERIAL mode.  It’s pretty easy, you
> drop the chip select, toggle the clock line up and down while also setting
> the data line to either low or high, then bring the chip select high again
> after the prescribed number of bits have been transferred.  The exact bit
> sequence, number of bits, etc are all DDS chip specific, as are the
> specific signal names, but they all used this same general principle.
>
> Some of the DDS chips also have parallel inputs, but most people did not
> mess with parallel data loading.  It was faster to load, but harder to
> implement the hardware.  I don’t remember anyone using the serial port, as
> the DDS chips don’t talk async serial.  You would need to use only the
> RS232 CONTROL lines (not the data lines), and bit-bang those lines with a
> software serial interface.  Plus, the voltages are wrong on a true RS232
> serial port.
>
> You should probably use a driver/buffer chip between the PC parallel port
> and the DDS chip, to protect the DDS chip.  I found that I used a 74HC244
> as the buffer.
>
> If you look at the AD9850 on the Analog Devices web site, there is
> probably a development or demo board that used the chip, and was driven by
> a PC parallel port, from what I remember.  Of course, parallel ports on PCs
> are getting harder to find.
>
> The Brainerd DDS/receiver boards had a good following, and there was some
> PIC code that could be used either on the Brainerd AD995x board, or other
> DDS chips, with the Spark Fun “UBW” USB Bit-Whacker board.  Both used a
> variant of the PIC 18F2550 chip for control.  Windows programs were written
> to drive the PIC chip, via the USB connection.  The original code was
> written by Tom (can’t remember callsign), but another ham and I added a LOT
> of additional support to it, including support for many other DDS chips,
> A/B VFOs, Tx/Rx switching, offsets, variable clock freqs and multipliers,
> and other stuff.  That code is still out there on a Yahoo web site.
> including C source code.
>
> I haven’t played with these DDS chips in a while, as the Si570 kind of
> took over, but I still have several of the older boards, and some of the
> old code.  Most of the code could be translated to an Arduino, except the
> Arduino doesn’t have great math libraries.  I’m not sure that you can get
> an accurate calculation of the FTW (Frequency Tuning Word) that needs to be
> sent to the DDS chip, but you may get within a few Hertz or tens of Hertz,
> which may be good enough.  I had to do a lot of messing around to get the
> larger FTWs working on the PIC chip, as it also had math library issues.
>
> Anyway, I might be able to find some archived DOS-based C code to drive
> the AD9832 and AD9850, given a little time.  It was originally written for
> Run-C (a C interpreter), then Borland Turbo-C, my favorite tools of the
> day.  Otherwise, I can certainly help you with how to program the DDS.  If
> you can find a PC with a parallel port, that’s a good start.
>
> The AD9850 is rather long-in-the-tooth, and somewhat poor in spurious
> signals, but these modules are certainly cheap enough!  I hope this helps.
> 73, Terry, WB4JFI
>
>
>  *From:* Alex Fraser <beatnic at comcast.net>
> *Sent:* Saturday, March 16, 2013 5:07 PM
> *To:* tacos at amrad.org
> *Subject:* AD9850 DDS
>
>     I got a package in the mail all the way from China.  I bought 3 of
> these AD9850 modules on ebay
>
> http://www.ebay.com/itm/400385385193?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
> My goal is to be able to generate an RF signal which I can use in place of
> a crystal oscillator in a radio.
>
>     First the physical aspects.  The 10 pins are spaced .1 apart and the
> two rows are what looks like .8 from each other.
> I first tried sticking them on a PATA hard drive cable and that works,
> though I only need one row.  I then remembered I had some plastic
> breadboards
> stashed away, which amazingly I found right away, so I can start right
> away trying to do something with these modules.   I imagine there will be
> some frequency limitation on using them on a breadboard, but to start I can
> use the lower range of their frequencies.
>
>     Has anyone used these? Anyone know of some good sites online on how to
> get these things  working in Ham radio?  I think eventually I would want to
> be able to control them with a independent little gizmo, but to start now I
> would be very happy to control them from a PC.  I would need to know what
> interface to use, like serial port or parallel port and probably need some
> help with software to push the desired signal out of the port.
>
>     I'm getting ahead of myself and haven't even got any lights to light,
> but if these boards, with those pin spacing would fit on an Arduino proto
> typing shield and folks thought it feasible (easy enough for a newbie!)
> then I would start acquiring the hardware now to do just that.
>
> --
>    \\\\\\\\\\\\\\\\-----++++*0*++++-----//////////////////
>        No electrons were harmed in the creation of this message
>          --------------------------------------------------------
>  ~~~********************Alex Fraser********************~~~
>          --------------------------------------------------------
> [[[[[[~~^^^#___=>>>```/\/\**O**/\/\```<<<=___#^^^~~]]]]]]
>
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> --
>    \\\\\\\\\\\\\\\\-----++++*0*++++-----//////////////////
>        No electrons were harmed in the creation of this message
>          --------------------------------------------------------
>  ~~~********************Alex Fraser********************~~~
>          --------------------------------------------------------
> [[[[[[~~^^^#___=>>>```/\/\**O**/\/\```<<<=___#^^^~~]]]]]]
>
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