As part of my ongoing project to come up better pedal assist for cheap ebikes, I bought an X9C104 digital potentiometer module from Bezosmart. This was one of my once or twice a year purchases I allow myself from that website, and what I got is counterfeit!

The common demo sketches all seem to have the potentiometer create a triangle wave or sine wave, but I was ending up with flat tops on the tops of all of my wave forms. I thought maybe something was wrong with the code, so I tried different code and got the same result. I tried a different library, and got the same result.

i looked online and found a few results where people were complaining about this in forums. most of the replies were to the effect of "You're doing it wrong."

One reply though suggested that sometimes these chips are counterfeit and suggested that could be the problem.

With that in mind, I did some troubleshooting and discovered that my X9C104 chip only has 30 resistive steps instead of the 100 it's supposed to have.