Motion Profiling with Pathfinder and Talon SRX

[ozdave]

Thank you

[Jaci]

@ozdave

Bit off topic for this thread, but it looks like a group of MP experts so I will ask.

We spent this weekend working on MP with Talon SRX, using the CTRE example code as a base. This is the first time we have worked with MP.

The profile is running, but we do not seem to get any indication that the profile has completed. The main control loop relies on the status returned from the Talon having the 'isLast" flag set true, and it never seems to come true.

Is this a know issue, or are we doing something incorrectly?

Secondly, currently looking at Jaci’s code for MP - looks pretty good to me. Comments on this approach versus using the Talon local MP?

Regards

David

Seems my reply to this got lost in transit.

Oblarg is correct, you need to set the isLast flag on your TrajectoryPoint you are loading, since there is no guarantee the end of the Talon’s internal buffer is the total size of the points.

In terms of RoboRIO-MP (Pathfinder style) as opposed to Talon local MP, the Talon local MP has the advantage of being fast and easy, whereas with an external loop (like Pathfinder’s followers), you can integrate other sensors like the robot gyro (you can do this with the SRX as well, but only with a Pidgeon IMU), as well as being able to use PWM/non-SRX controllers. Both work perfectly well, we’re loading Pathfinder-generated paths onto our Talons using their Motion Profiling interface, although this may change soon.

[ozdave]

Thanks Jaci - really appreciate the guidance.

[Ty_Tremblay]

FWIW, 319 wanted essentially the same thing. We wanted to follow 254’s trajectories from 2014, but using the SRX’s motion profile capabilities.

Here’s what we came up with:

Team319/BobTrajectory

And here’s how we follow a trajectory generated and put on the rio:

Team319/frc319-2018/blob/master/src/org/usfirst/frc/team319/robot/commands/FollowTrajectory.java