View Single Post
  #6   Spotlight this post!  
Unread 31-01-2010, 11:59
Mr. Lim Mr. Lim is offline
Registered User
AKA: Mr. Lim
no team
Team Role: Leadership
 
Join Date: Jan 2004
Rookie Year: 1998
Location: Toronto, Ontario
Posts: 1,125
Mr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond reputeMr. Lim has a reputation beyond repute
Re: maximum rpm for encoder.

Anecdotally,

we are sampling at 20,000 cps without any difficulty using the kit-supplied encoders.

This is using the 4X sampling feature, which is enabled by default. This means even though the encoders produce 250 cpr, the cRIO is actually able to read 1000 cpr by capturing every edge transition on both phases.

My related question is:

I've noticed in the WPILib documentation that the FPGA is only mentioned when using the 4x encoder mode. In 1x mode, the documentation mentions that a Counter object is used instead. If we use 1x mode, is the FPGA NOT used to count pulses? If the FPGA is not used, does this reduce our maximum count rate by more than a factor of 4? Does this basically mean the 4x mode is always our best bet when using encoders?
__________________
In life, what you give, you keep. What you fail to give, you lose forever...
Reply With Quote