Kevin,
The board is not defective. There is something wrong [or at least different] with that scale. I can't help you more without either you capturing the outputs of the scale via an oscilloscope while it's jumping or sending the scale to me so I can do it.
Also, just to set the record straight, I've been trying to help you since October. Here is a quick recap:
You bought the adapter in July of 2018
In October of 2020, you sent it to me to look at, and even though I wasn't able to reproduce the issue, I replaced the board with the new revision.
In February of this year, you complained that the problem has gotten worse and sent the new board back. I reprogrammed it with the new firmware version and tested the crap out of it with the scales I have. I even sent you 3D-printed standoffs to isolated the scale from the machine's body. The problem didn't go away on your end.
I offered to test the scale and tell you exactly what's wrong with it if you send it to me. If there is something wrong on my end, I will cover the shipping. That said, I sell hundreds of these boards per year and on a bad year, I get no more than ten-ish boards with ANY issues (defects and customer damage). It's extremely unlikely that there is a bug in the firmware that is causing this problem, especially since yours is the only case with these symptoms.
In the few cases, I've seen before. the scale was bad, but those scales didn't work with the original display either. I don't have access to the iGaging code, so I don't know what magic they are doing to make that scale not jump. It's possible that there is something different with the signal timing. iGaging scales flip the data bit on the rising edge and need to be read on the falling edge of the clock signal. TouchDRO uses interrupts, so it reads the bit within a few nanoseconds of the falling edge. it could be that the data line is either not changing fast enough, or there is some jitter that is triggering the interrupt at the wrong time.
It's plausible that the signal either doesn't fall fast enough (and the display somehow can compensate for it) or more likely, there is some sort of jitter that the display doesn't catch and TouchDRO does. I can probably see that pretty easily on the scope, but I can't afford to be sending you new boards in hopes that one of them will miraculously work.
Regards
Yuriy
