Quote:
Originally Posted by Necroterra
So if I understand this DMA thing, the FGPA reads off the sensor values on an event happening, and the relatively slow accessing of the memory can be done later? Wouldn't that still give you inaccurate data unless you added on the expected change since it was read?
Also, by upstreamed, do you mean it will be part of default WPILIB?
|
Yes, part of WPILib. I sent out patches in December ish, but there were too many other issues for the patches to get much attention.
With DMA, you get to read the captured data when you want. But, that capture can include both the signal that changed, all digital inputs, the timestamp of the event, all encoder values, all analog inputs, etc. If you are trying to correlate a digital input change to an encoder value, that delay is fine. If you are trying to correlate an analog input with an encoder at an edge, the delay is also fine. And by delay here, I mean up to 5 ms for our system, since we run our control loops at 200 hz and only pull out of the DMA buffer at that frequency.