Hi Janne, Analog Devices' data sheet on AD9951 is not very clear if not confusing, it took me a while to understand it too. My advice would be to use DL5MGD's program first to test your hardware platform, you can then try to write your own code. This is exactly what I did. Basically I control the DDS using the "serial" mode, freq data is sent as 40 bit long serial data stream. Initially you need to send other commands (in serial also) like 'reset' and ref clock multiplier (cfr2_mult, if you are using the multiplying scheme). Try downloading codes from other Yahoo groups like IW3HEV's VNA and AD9954 DDS. 73 de DJ/NM3R
----- Original Message ---- From: iami78 <[EMAIL PROTECTED]> To: [email protected] Sent: Wednesday, March 14, 2007 8:27:59 AM Subject: [soft_radio] Re: Single AD9954 with counter or dual AD9954 to form IQ VFO. --- In [EMAIL PROTECTED] ups.com, "D. J. Wang" <[EMAIL PROTECTED] > wrote: > >Hi Janne, >I have built two boards, one with AD9951 and another with AD9954, >since they have the same pinouts, I used an identical PCB design. The >most difficult part is line up all 48 pins and solder them, there >wasn't that many external parts to solder after that. >I agree that using the internal multiplier is not a good idea as it >generates a lot of spurious signals but I was just trying to get it >working as quickly as I can. DL5MGD published the PIC hex code and a >VB prgram so you can control it with an 16F877 or thru printer port. >That make thing a lot easier. I would have to rewrite it if I change >the reference clock frequecy and multiplication factor. Later, I did >write some AD9951 control code when I get more familiar with teh DDS >chips and modify IW3HEV's VNA program to drive my AD9954, it turns >out it was not as difficult as I original thought. >DL5MGD's design is pretty good and you certainly can improve the >spurs by using an external 500-550 MHZ clock. I0CG's design uses a >XTAL OSC at 100 MHz or so and filter out unwanted harmonis. Spur >improvement probably depends on how clean the 100MHz osc you will be >using. > >73 de DJ/NM3R Hi D.J.! I'm pretty sure that this whole DDS language will become really clear after you once dive into it - just like you mentioned. Too bad that we don't have any DDS experimenters at our club or even on the bands. Seems like DDS is still a little bit underground among ham radio operators. Anyways, I started to draw the circuit board, and yes, it has two AD9954. I'm gonna do the hardware and then dive into the software thing. What I can't really figure out is, how do I sent the commands to the DDS chip. If I want to for example just change the frequency, do I sent FTW0(xxx) in ascii format. Because the DDS chip isn't cpu, I think that you first send the register number and after that the value? As you may notice, I don't have the slightest idea. 73 de Janne, OH1GTF ____________________________________________________________________________________ Get your own web address. Have a HUGE year through Yahoo! Small Business. http://smallbusiness.yahoo.com/domains/?p=BESTDEAL [Non-text portions of this message have been removed]
