[aldaeron]

If I read your post correctly - the signal for the Talons is being set via the smart dashboard instead of the controller, therefore you can rule out the controller.

I would unhook the gyro and comment out any code that refers to it.

As a general rule for troubleshooting: you want to start from a known good state and add things back in until you find the problem. In your case this means getting two motors working such that the robot drives straight and then add Talons and motors back in until you get 4 motors driving straight.

Some troubleshooting step I would look into:
- Are the transmissions greased properly and equally? Does one have a lot more old yucky grease?
- Are the gears inside each transmission identical? We have had different gearings in "identical" transmissions before. Same goes for any belts idlers or chain sprockets. We had a bot where the left and right chain sprockets attached to the gearbox were different tooth counts so it always moved left.
- Can you spin the gearboxes by hand with approximately the same force without motors while on blocks?
- When on blocks and set to coast - if you go from 100% power to 0% power do the wheels stop at about the same time?
- Are all the motors and controllers the same vintage (i.e. is one motor re-used from 2013)?

What encoders are you using?

Did you calibrate the Talons on blocks on the actual robot or calibrate them on a different electronics setup and then add them to the chassis?

Are the PWM cables in good shape and making good contact?

Have you tried other PWM ports on the Digital Sidecar? I have seen a few CD posts where the PWM ports weren't working properly (though this is rare).

With the robot on blocks - are the Voltages on the outputs of the Talons very close to each other?

If you still still see errors start switching components (Talons and Motors) one at a time and take careful notes of what was changed and whether the robot went straight, right or left. Theoretically when you swap the underperforming Motor or Talon from left to right it will drift the other way. This is easier to do with a single motor on each side. If you have motors A,B,C,D and Talons 1,2,3,4 try something like:

Talon 1 with Motor A on the left and Talon 2 with Motor B on the right, then
Talon 1 with Motor B on the left and Talon 2 with Motor A on the right,
etc.
until you find out which Talon or Motor is not playing nicely.

We have had a few hiccups using Talons for the first time this year but eventually sorted them out.

Drive up and visit us in Denver Tuesday if you're still having trouble. We still owe you for setting up such a great off-season event.

-matto-