Tutorial 03: Buttons

You will build: a test program that shows every kind of button job on telemetry. The main track puts buttons in one file for you: Buttons.

You will learn: every kind of button job (press, hold, release, toggle, triggers), how to give the driver feedback with rumble, how to step through a list with the D-pad, and why the “held through START” guard matters.

You need: a Control Hub and gamepads 1 and 2. No motors: everything shows on telemetry.

Full program: Tut03Buttons.java Reference: gamepad.md

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1. The problem buttons have

The loop runs about 100 times per second. If you write

if (gamepad1.a) presses++;

one quick tap adds about 10, because A stays “down” for about 10 trips around the loop. You usually want one action per press. Doing that by hand needs an extra variable for every button. ControllerBindings does it for you, for every button at once, and keeps all the button jobs in one list that is easy to read.

2. The kinds of jobs

ControllerBindings controls = new ControllerBindings()
        .bindPress(Pad.G1, Btn.A, () -> presses++)          // once, when A goes down
        .bindHold(Pad.G1, Btn.B, () -> holdLoops++)         // every loop while B is down
        .bindRelease(Pad.G1, Btn.X, () -> releases++)       // once, when X comes up
        .bindToggle(Pad.G1, Btn.Y,
                () -> { slowMode = true; confirm.play(true); },     // 1st press: ON
                () -> { slowMode = false; confirm.play(false); });  // 2nd press: OFF

Which one to use:

You want	Use	Example
do something once	bindPress	open the claw, go to a set height
keep doing it while held	bindHold	run the intake while held
something when let go	bindRelease	stop the intake when the button is let go
a mode that flips on/off	bindToggle	slow mode, field-centric

Pad.G1 is gamepad 1 (the driver); Pad.G2 is gamepad 2 (the operator).

Two jobs, one action

.bindPress(Pad.G1, Btn.A, () -> presses++)
.bindPress(Pad.G2, Btn.A, () -> presses++)

Either driver can do it. You can also put two jobs on ONE button; they run in the order you added them.

3. Feedback with rumble

A toggle is invisible: the driver cannot tell if slow mode is on without looking at the screen. ToggleRumble buzzes the gamepad: two buzzes = ON, one buzz = OFF.

ToggleRumble confirm = new ToggleRumble(gamepad1);
...
() -> { slowMode = true; confirm.play(true); }

Use the same rule for every toggle on your robot, so drivers learn it once.

4. Choosing from a list with the D-pad

static final String[] HEIGHT_NAMES = {"Floor", "Low", "Middle", "High"};
private int heightIndex = 0;
...
.bindPress(Pad.G1, Btn.DPAD_UP, () -> heightIndex = Math.min(heightIndex + 1, HEIGHT_NAMES.length - 1))
.bindPress(Pad.G1, Btn.DPAD_DOWN, () -> heightIndex = Math.max(heightIndex - 1, 0))

HEIGHT_NAMES is an array: a list of values in one variable. heightIndex is the place in the list, counting from 0, so HEIGHT_NAMES[0] is “Floor”. Math.min and Math.max stop the number at the ends of the list, so it can never point past it. Tutorial 12 turns this into a neat LiftHeights list with up() and down().

5. Triggers

Triggers are not on/off; they give a number from 0 (let go) to 1 (fully pulled).

.bindTriggerPress(Pad.G1, Trigger.RT, () -> shots++)          // once per pull past halfway
.bindTriggerAxis(Pad.G1, Trigger.LT, value -> leftTrigger = value)   // the value, every loop

• bindTriggerPress / bindTriggerHold treat the trigger as a button: “pressed” means past 0.5. Change that with .setTriggerThreshold(0.8) if drivers fire by accident.
• bindTriggerAxis hands you the number every loop. value -> ... is a lambda with one input.

6. The “held through START” guard

waitForStart();
controls.ignoreHeldButtons(gamepad1, gamepad2);

Drivers often hold a button while the match starts. Without this line, a held button’s press job runs in the very first loop: a surprise action at the start of the match. With it, any button held at START does nothing until it is let go once.

7. The loop

while (opModeIsActive()) {
    controls.update(gamepad1, gamepad2);   // once per loop, before you use the results
    ...telemetry...
}

Run it

1. INIT. Hold A, press START, keep holding: the A count stays 0. Let go and press: 1.
2. Tap A quickly many times: exactly one per tap.
3. Hold B: the “loops held” count runs up fast. That is bindHold.
4. Press and hold X: nothing. Let go: +1. That is bindRelease.
5. Y: two buzzes and “Slow mode : yes”. Y again: one buzz, “no”.
6. D-pad up and down: the height name changes and stops at Floor and High.
7. Pull the right trigger past halfway: one shot per pull. Squeeze the left trigger: the number follows it.
8. Gamepad 2’s A also counts.

If something goes wrong

Problem	Fix
Nothing happens	Is controls.update(gamepad1, gamepad2) inside the loop? Is the gamepad assigned (Start+A for gamepad 1, Start+B for gamepad 2)?
A counts many times per press	That job uses bindHold. Use bindPress.
No rumble	Some gamepads have no rumble motors. Logitech F310 does not rumble.
“Cannot assign a value to final variable”	The variable must be a field (see Tutorial 01).

Try this

1. Make the right bumper toggle a “turbo” mode with its own rumble confirmation.
2. Make the D-pad list wrap around: up from High goes to Floor. (Hint: % HEIGHT_NAMES.length. % gives the remainder after dividing, so it wraps 4 back to 0.)
3. Use bindHold and bindRelease together on gamepad 2’s A: hold = “intake running”, let go = “intake stopped”.
4. Change the trigger threshold to 0.9 and feel the difference.

Next

Tutorial 04: Drive a mecanum robot or Tutorial 05: Drive a standard (tank) robot