Difference between "slotIdx" and "pidIdx"

[Wibis428]

There are a handful of functions that require either a "slot index" (slotIdx) or a "pid index" (pidIdx) parameter:

talon.configSelectedFeedbackSensor(FeedbackDevice feedbackDevice, int pidIdx, int timeoutMs);

talon.setSelectedSensorPosition(int sensorPos, int pidIdx, int timeoutMs);

talon.selectProfileSlot(int slotIdx, int pidIdx);

talon.config_kp(int slotIdx, double value, int timeoutMs);

talon.configAllowableClosedLoopError(int slotIdx, int allowableClosedLoopError, int timeoutMs)

From what I've read in the documentation, the talon is capable of storing 4 different "Motor Control Profiles" (pg. 72 of software reference manual). One motor control profile consists of one set of PID loop gains and a few other closed-loop preferences. Am I correct in assuming slotIdx refers to one of these motor control profiles? This makes sense to me, as talon.config_kp() and talon.configAllowableClosedLoopError() would need to know which motor control profile to apply the config to.

As for pidIdx, the only documentation I can find says that pidIdx should be "0 for primary closed loop, 1 for cascaded closed loop". I can't find anywhere where it's specified what this actually means, so I don't understand why talon.configSelectedFeedbackSensor(), talon.setSelectedSensorPosition(), and talon.selectProfileSlot() require this parameter. In every example usage I've seen of functions that require pidIdx, it's always passed in as 0 and never as 1. What's the point of this parameter, and how is it different than slotIdx?

Thanks in advance!

[laviRZ]

If you look at the documentation of BaseMotorController.selectProfileSlot() you'll see the following:

/**
* Selects which profile slot to use for closed-loop control.
*
* @param slotIdx
*            Profile slot to select.
* @param pidIdx
*            0 for Primary closed-loop. 1 for auxiliary closed-loop.
**/

So I would infer that the slotIdx refers to one of the four sets of PID values. From the documentation: "Closed Loop controller will pull closed-loop gain/setting information from a selected slot. There are four slots to choose from (for gain-scheduling)".

And pidIdx would refer to whether you want to use the regular closed loop PID (PID[0]) or the Auxiliary closed loop (PID[1]).