DDS Up and running
Sun, 13 Jun 1999 15:20:32 -0400
Just a note to let you know that the first DDS module is up and
running. I built a simple breadboard around the module, and tickled it
into working the first time!!
As a reminder, it is a Analog Devices AD9832 and 25MHz oscillator
sitting on a small board that mounts onto a 24-pin DIP header. It can
be programmed (via 3 wires) from almost 0 to about 9 MHz in .025Hz
steps. I use bits D0, D1, and D2 of the printer port as clock, data,
and select lines. In addition, it has 2 frequency registers selectable
by software or a hardware pin, and 4 phase registers, also selectable by
software or 2 pins. FSK, BPSK, or QPSK is easily achievable.
The module generates about 1V P-P, and it does not include a low-pass
filter. For simple applications, I have used a 5-pole LP filter, and an
Analog Devices AD818 op-amp buffer. If I want a square wave, I raise
the gain of the op-amp and feed it to a schmidt trigger.
I have enough parts to make about 10 modules, and think the parts are
still around $25.00. I will put some more together, and prepare some
simple documentation. Anyone interested in writing software?????
I can think of a lot of applications, and software to write. RF
sweeper, FSK or PSK generator, etc. I will also use them for the LO on
my LF receivers. Remember, the hard part is done, the rest is only