These notes describe a DOS control program for an AD9850 
frequency synthesizer using serial input.  It is a 
reworking of a program I did about ten years ago.  Not all 
of the features of the original are applicable to this 
synthesizer, and not all are functioning at this time in 
this early release.  The description below is of features 
currently implemented.

Hardware:

Serial or parallel port control allowed.  Parallel port is 
recommended because it is at TTL levels and doesn't require 
level translation.

Program use and features:

Frequency control may be done by use of the UP & DOWN arrow 
keys or by direct keyboard entry.  When adjustment is by 
the arrow keys, the current step is used.  Steps of 1, 5, 
10, 50, 100, 500 and 1000 Hertz are selectable. Step size 
is increased with the Right Arrow key and decreased with 
CONTROL-Right Arrow.

There's a Memo memory.  ^-S stores the current main 
register into this memory and ^-M swaps the main and memo 
registers, thus putting the stored frequency into the 
synthesizer.  The quickest way to jump to an alternate 
frequency and back.

There's also a bank of 16 additional memories.  PG-DN 
enters the memory mode.  Arrow up and down keys select 
memories.  Arrow-Right stores the current main register 
into the selected memory.  Arrow left moves the selected 
memory to the main register and quits the memory mode.  PG-
UP quits the memory mode without changing the main 
register.  Each memory has a free text field where you can 
record the reason you recorded this frequency, such as a 
net, calling frequency name, or DX call heard.

There's a SCAN function for the memory mode, started by 
pressing S.  Speed of the scan is adjustable.  Individual 
memories may be locked out of scan.

In addition to memory scan, there's also a BAND SCAN 
function.  You set the high and low limits and begin the 
scan, which repeats continuously.  The frequency step is as 
you selected previously and the scan rate is adjustable 
during the scan with the arrow keys. You can pause the scan 
with the spacebar, and move the paused frequency to the 
main registers with the Up Arrow key.

There's a main help screen accessed with F1 giving all main 
command keys, plus mini-help screens according to context.  
There's also a "hardware" help screen [F6] giving the 
connector pins to use for serial or parallel control.  
A mini-help screen that doesn't cover any normal information 
fields can be turned off and on with the F3 key.

The (new) 'O' (oscillator) command allows you to select 
from two timebase frequencies: 100 MHz and 120 MHz.  This 
is to accommodate the NJQRP (100) and Trevor Jacobs (120) 
versions.  I should add more choices, but the calibrate 
routine will let you customize the timebase frequency to a 
different value.

The (new) 'C' (calibrate) command lets you adjust the value 
used for the oscillator (timebase) frequency to allow for 
minor inaccuracies in oscillators. You can do this for any 
frequency you have a standard for (or use a frequency
counter).  When you enter the mode, you adjust with the 
arrow up and down keys until the output frequency of the 
oscillator matches the frequency of the standard.  At this 
point, press the space key and the program stores the 
corrected oscillator frequency for use from that point on. 
You can adjust the step change for calibrate mode to 1000, 
100, 10, or 1 hertz.  Note that the output frequency change 
is much less.  For example, at 10 MHz, a step of 1000 Hz 
in timebase frequency produces a 100 Hz change in output 
frequency. Just for fun, the actual timebase frequency as 
determined by calibration is displayed when you view the main 
help screen (F1).

There are Write (W) and Load (L) commands to save your current 
setup to a file.  You can also have this file autoload when the 
program starts.  All frequency registers are saved, including memories 
and memory notes, plus the timebase frequency as corrected by the calibrate 
command.

Another new feature is a quick selection of ham band frequencies.  
The commands are (-) to go one band lower and (=) to go one band higher.  
(Think of "=" as "+" without needing to press the shift key.)  
These commands cycle through the bands 160 through 10 meters with a 
stop also at 10 MHz WWV.

Another tweak is that you can now press [SPACE] to force the 
program to send the data to the synthesizer.  This is in case it
lost the info somehow.

All registers--main, memo, scan limits, and 16 memories, 
are visible on screen at all times.

STUFF NOT UPDATED OR VERIFIED YET:

RIT and XIT control.  This program was originally written 
for a synthesizer that had two frequency registers, so the 
program could load them both independently.  The AD9850 
doesn't have this.  However, I still want to implement 
something similar even though loading in the 40 bits may 
take a little too long for QSK T/R swapping.  The idea 
would be to have a separate T/R status line to the port 
(serial or parallel) and when the program senses that the 
'T' line has been asserted, it will immediately load TX 
frequency data.

Nick Kennedy
WA5BDU

kennnick@gmail.com   is my email address.