LabVIEW Encoder not reliably returning Rate

[apalrd]

Hello, all.

Yesterday, I was testing and tuning some code on a test chassis. It has two Toughboxes and US Digital encoders (from AndyMark, 250 count) connected to the last four digital inputs on the Digital Sidecar. In code, I found that Encoder Get does not reliably return Rate: I always get Distance (which I found to be accurate in both forward and reverse, by drawing a line on the wheel and reading the distance both ways. Only one of the encoders returns rate, though, which puzzles me. What puzzles me even more is that when I set the Decoding Type to 4x (Because that uses an FPGA Encoder instead of an FPGA Counter) it works - but only until I reboot (when the problem happens again, and is fixed by switching back to 1x).

I dug into the WPI Encoder Get to see if there was a bug there. WPI Counter Get is returning a time of Inf, which Encoder Get is scaling to 0. I went into WPI Counter Get, but that just talks to the FPGA (meaning I cannot dig deeper). When I first had the issue, I probed the Dev Refs and the non-working encoder was using Cntr 1 while the working encoder was using Cntr 0. I did not probe them using the 4x decoding, but when using 4x decoding, the other side (the one that worked before) now has the issue.

I am sure all of the hardware works. I swapped the encoder wires (Between encoders) and the problem is not the encoder itself. I also know that I am not missing the B-phase, because it counts forwards and backwards. Everything I have looked at points to a bug in the FPGA encoder handling, I am using the latest 2011 image. (I guess I could try the 2010 image to see if it works, but I won't have access to the robot until Monday).

Has anyone seen this issue? How did you solve it?