AD9832 Hopping

Terry Fox
Tue, 09 Feb 1999 20:09:52 -0500

This morning I sent the AD9832 commands to hop between 2 frequencies,
and monitored the PC output port.  Using a Toshiba 400CS laptop, which I
believe is a 4 year-old Pentium 75 or 90, it takes a disappointing 75
microseconds to send the 32 bits to move the AD9832 to another
frequency.  This translates to about 13,333 hops per second!!  The
limiting speed is the bit-banging through the PC parallel port.  Using a
PIC, or hardware shift register fed from the parallel port could speed
this up.

Another speed improvement could be made by programming only half the
bits, and leaving the other 16 bits as they were.  This would reduce the
frequency resolution, but double the frequency update rate.

In addition, if I bring out the RSET pin and drive it externally, the
amplitude output can also be controlled to a limited extent.

By the way, Sandy:  the 9832 is upside down on the board, in case you're

That's all for now.