tapwithus/tap-android-sdk/tap-android-imu-motion

IMU motion and mouse

The two BLE protocols report motion on different callbacks. Both can be connected at once; branch on sdk.isV2Tap(id). That check is the framed protocol, not a second SDK.

Framed protocol: IMU motion

Controller mode enables DeviceFeature.IMU_MOTION_DATA on connect. You can also call sdk.setFeature(id, DeviceFeature.IMU_MOTION_DATA, true) after onTapConnected.

@Override
public void onImuMotionInputReceived(String id, ImuMotionPacket packet) {
    int dx = packet.dx;
    int dy = packet.dy;
    boolean isMouse = packet.isMouse;
    int roll = packet.roll;
    int pitch = packet.pitch;
    int yaw = packet.yaw;
}

override fun onImuMotionInputReceived(id: String, packet: ImuMotionPacket) {
    val dx = packet.dx
    val dy = packet.dy
    val roll = packet.roll
}

• dx, dy: signed pointer deltas since the last packet. Add them to a cursor position.
• isMouse: true when the device treats the motion as pointer movement.
• roll, pitch, yaw: signed orientation in degrees.
• Turn the feature off with setFeature(id, DeviceFeature.IMU_MOTION_DATA, false) to save battery.
• Motion works together with MODEL_DETECTION (air gestures). The tap-android-knob and tap-android-dpad skills combine them.
• Classic firmware does not call onImuMotionInputReceived.

Classic protocol: mouse events

Controller mode (or controller-with-mouse HID) delivers:

@Override
public void onMouseInputReceived(String id, MousePacket data) {
    int vx = data.dx.getInt();
    int vy = data.dy.getInt();
    int proximity = data.proximity.getInt();
}

• dx / dy: signed velocities (PacketValue.getInt()).
• proximity: non-zero when a surface is detected (optical mouse on Tap Strap).
• Classic packets have no euler angles. For orientation on classic firmware, use raw IMU (tap-android-raw-sensors).
• Choosing air-mouse versus tapping on TapXR is startXRAirMouseState(id) / startXRTappingState(id), not a separate input-type enum.

The framed protocol also forwards pointer deltas on onMouseInputReceived. Prefer onImuMotionInputReceived when you need roll, pitch, and yaw.

Patterns

Post to the main thread before touching a View.

Cursor (clamp to bounds, optional gain):

float x = 400, y = 300;
void onMotion(int dx, int dy) {
    x = Math.max(0, Math.min(width, x + dx * gain));
    y = Math.max(0, Math.min(height, y + dy * gain));
}

Relative rotation (roll as a dial): store the roll when the user starts (for example on a pinch-hold), then use roll - reference. Do not use absolute roll. It depends on how the hand is held. See tap-android-knob.

Smoothing: smooth = alpha * value + (1 - alpha) * smooth with alpha around 0.3.

Dead zone: ignore Math.abs(dx) + Math.abs(dy) < 2 so a still hand does not drift.

Rate: count packets per second if timing matters. Do not assume a fixed rate.

If a direction is inverted on the user's device, flip the sign. Ask the user to test and tell you.

Docs in this repo

• ImuMotionPacket and MousePacket: tap-android-sdk skill, reference.md
• Example app handles mouse and air-gesture rows in MainActivity