Quote:
Eric,
Now that the math has been simplified by making the input control range -1 to 1; how many places of resolution after the decimal point does the Jaguar have? In other words, will sending .2508 be any different than sending .25? I realize this is only a .32% difference, but I am really looking for the limitations that the input has on it, not the actual output. Would anything over 2 places even be read by the Jag?
|
Quote:
Originally Posted by Alan Anderson
The resolution is limited by the cRIO Digital outputs before the Jaguar sees the signal in the first place. The outputs have a 6.625 microsecond update rate, so there are only about 150 different pulse widths possible between the 1ms and 2ms limits of a standard servo-type signal.
|
Bill -
Alan's post is only half correct. It is true that the outputs have a 6.625uS update rate, which does equate to 150 signals over the standard window.
However, this is slightly higher resolution than the Victors can respond to. Additionally, the Jaguar does not use the standard 1ms - 2ms window by default (it can be set to do so). It uses a wider window in order to get more resolution. This is why you must use the Jaguar or Victor specific API calls - they will scale the pulse width accordingly.
I don't have access to the exact numbers right now - I've managed to get out of the office this weekend. Hopefully someone with better knowledge of the specifics will jump in.
I'm 30% confident that internally, the Jaguars represent the Duty cycle with a 16 bit number (even though they are using a 32 bit processor). I'd be surprised if we are getting more than 8bits over the PWM channel, so this extra resolution isn't used (this year).