Hey, #Electronics folks!
Has anyone seen such an output for a ramp coming out of a DAC?
This is produced by a simple counter counting from 0 to 4095 and then wrapping.
The sharp dips are absolutely stable and deterministic. They occur at bit switches but I don't seem to get my head around why.
Identical curves on two different DAC peripherals on the same μC and even across different chips/boards (I'm almost certain it's a software problem).
@cweickhmann Is this a DAC with a parallel interface or serial?
@cstanhope
Do you mean bus-wise or analog front end?
It's a ATSAME51J20A and sort of vague on either of that. It is on-chip though, it supports DMA, I'd assume it's serial.
Front-end side there's nothing in the datasheet. At 12 bit it's certainly something more elaborate than a simple resistor ladder, but not clear what.
@cweickhmann That's a very fancy DAC on there. It has dithering modes and other kinds of things.
@cweickhmann I can't quite tell looking at your scope picture and based on my ignorance of your setup, so I'm going to ask a very obvious question, which I'm sure you've already thought about so I do not mean any offense by it. You've ruled out aliasing on the scope display? In other words, you've got the right time base for what it is you're looking at?
@cweickhmann Okay, I was thinking it was its own device. My first thought is that maybe bits are somehow being swizzled. A parallel interface wired up wrong could easily do that. But I suppose it's possible to also get a serial interface wrong too, with either bit order or word order etc. But since it's on device, it's has to be something else. Somehow driving it incorrectly or having it in the wrong mode or something.