USB interfacing, Using a DLP245PB, I get very bad ringing on the data lines

The DLP245PB is a USB interface board that can be plugged into a
breadboard

It uses a PIC 16f877 Microcontroller, and an FTDI245 chip to
handle USB calls
I current;y have it powered directly by the USB port and
connected to my laptop.

My big problem though is that when I try to use it to
control/increment the clock on a digital potentiometer (an X9C103) in
order to adjust the resistance, I keep getting some very unpleasant
ringing on the line.

I need this interface to work in order to be able to program a
control system for a graduation project, and I need to be able to kill
the 20 microseconds of ringing the circuit seems to have. I know that
it is not my software (not drivers or anything else. My circuit is far
too simple to be directly responsible for this much ringing.

If there is no good fix, can anyone recommend a good alternative
to the devices from FTDI and DLPdesign? Something with a relatively
easy to use programmers API and a reliable (and affordable...student
budget affordable) circuit which can be used at close to the 1Mbyte/bit
/s range? I had some big plans for this equipment, and if I find out
nw that it is junk, I will be very Irate. Also, can anyone recomend a
network interface board that can be used along the same lines?

.

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