New Talon Speed Controller

[Mike Copioli]

Originally Posted by Gdeaver

The .9 to 2.0 ms with a 0 output at 1.5 ms asymmetric response confuses me. Why did they do this? This is going to lead teams to terrible out of the box experience. If the Talon is hooked up to the controller and the present Victor motor drive routines are used, then a team will not get full power in 1 direction. This will require calibration. One more step for teams to screw up. Which will lead to rants and support issues. The pulse timing is listed as 10 bit or 1024 buckets. With calibration there will be less settings in one direction than the other. Does it matter? probably no. The question this year will be " Did you calibrate your Talon." Response - "I don't know." "You have to calibrate your Talon." "How do you do that?" and on and on. Cross the roads - It's time for a firmware up grade before you let this thing out in the wild. Your life will be better if you correct this now before the Chief Delphi Flamming starts. Why was this done? Is it a clock counter timer issue? Asymmetric I don't like it. I don't remember ever seeing a commercial speed control with asymmetric response.

Ok,

Sit down, relax...I assure you the sky is not falling.

There were a couple typos in the user manual, the ACTUAL expected pulse width is 1.0-2.0 ms with the center = 1.5 ms. The user manual should have read .990-2.010ms. The reason for the 10 us gap is to over drive the pulse to ensure that any error in the input pulse does not cause the output to transition between full on and chopped. Let me make something perfectly clear; This is not necessary for the Talon to function smoothly or symmetrically, just a recommendation. On top of that the Talons firmware has 10 us(2%) of padding on each extreme of the input pulse.

Screwing up calibration is not really possible. The calibration values are checked against bounding values. If the cal values are outside of those boundaries the Talon will simply use the last "good" calibration values. The worst that could happen is truncation of the output.(full throttle is obtained at a lesser input value) But even then all you are really changing is granularity or resolution. Remember the Talon is 10 bit, the Victor uses 8 bit(which BTW is more than enough resolution)

Also to assume that you would only have two speed controller classes as before would be presumptuous. The Victor and Jaguar classes both use different timing parameters for full forward, full reverse and center. The Victor class uses 2.035ms = MAX, CEN = 1.526ms, MIN 1.032ms, this is also asymmetrical. If the Talon is deemed legal a Talon Class would most likely exist.

As far as calibration is concerned, if you are not already calibrating your PMW based motor controllers, you should be. Calibration not only corrects for pulse timing discrepancies, it also scales the out put MIN, MAX, and CEN to your joystick MIN, MAX and CEN.

So you can relax there is no need to upgrade your firmware, or flame the thread(although from my experience this will happen anyway). It was simply a mistake in the user manual.