Does your reader generate single ended TTL type signals or RS422 type differential signals?
Differential type signals will be MUCH more immune to external noise.
It sends the usual A and B edges, and NotA and NotB, each on a wire. But I suspect neither of the DRO heads I have (SINO and TouhDRO) do anything clever with the negated signals.Does your reader generate single ended TTL type signals or RS422 type differential signals?
If the DRO is only using the single ended TTL signals, that's really not great, chances are if it was using the differential signals your induced noise problems would simply disappear.It sends the usual A and B edges, and NotA and NotB, each on a wire. But I suspect neither of the DRO heads I have (SINO and TouhDRO) do anything clever with the negated signals.
What I really need to do is find a decent scoping point on the connections, and inspect the noise from the AC, but now that I've routed the cables differently I've lost my incentive to do so.
Yeah, I could see that helping. But now that I'm working, I'm loathe to touch it again... Thanks for the offer, however.If the DRO is only using the single ended TTL signals, that's really not great, chances are if it was using the differential signals your induced noise problems would simply disappear.
I could send you a PCB that has 3 x DB9's differential in with single ended outputs, that if you placed close to your DRO might solve the problem or at least help. ideally the differential to single ended conversion should be done as close as possible ( like a few mm) from the uC that is interpreting the signals. Either that or get a DRO with differential inputs.
The cables are almost certainly hand-assembled, and it might be easy to "miss" the grounding when putting them together.