Why would my old Uno work with a Digilent Pmod DA4, but my new Uno 3 does not?

Does anyone have experience with tempermental Digilent PMODs?

I have loaded the same test program onto both old and new Unos.
I have tested both with the same breadboard.

The Uno 3 does not successfully initialize the Digilent Pmod DA4. The old Uno does work, but stability is not perfect. I think it's now better with a decoupling capacitor, but the PMOD board should already have those.

One clue I have is that some folks mention that the DA4 is sensitive to power and has a lag time of possibly hundreds of milliseconds when it starts. I see that when I upload my code to my old Uno, the DA4 does not initialize; it's completely inert. If I then press reset a moment later, it initializes and runs.

Beyond that, I cannot explain why these 2 versions of Uno would behave differently. If I had not randomly tested my DA4 with the old Uno, I would have assumed it was damaged.


The header sockets in the Uno 3 are loose in comparison to my old Uno. And, the PMOD DA4 worked better after I slightly bent its pins to fit my 6-pin header. I will repeat my tests taking this into consideration.

No, this is not a matter of poor electrical connection.