Arduino Pinball Accelerometer (Nudge Controller)

Turns an ATmega32U4 board (Arduino Leonardo, Pro Micro, etc.) plus a 6-axis accelerometer into a USB joystick for virtual pinball software (VPX, Future Pinball, etc.). Tilting/nudging the cabinet moves the joystick X/Y axes so the software can register table nudges and tilts.

The original version targeted the MPU-6050, which is now discontinued. This version drops it in favor of three parts that are all still in active production, and the same sketch works with any one of them by changing a single line.

Supported sensors

Pick one — wiring (SDA/SCL/VIN/GND) is the same I2C hookup for all three, only the address/library differs:

Sensor	Library to install (Library Manager)
TDK ICM-42688	DFRobot_ICM42688
Bosch BMI270	SparkFun BMI270 Arduino Library
ST LSM6DSOX / LSM6 family	Adafruit LSM6DS (+ Adafruit Unified Sensor)

You also need the Joystick library by Matthew Heironimus (Sketch → Include Library → Manage Libraries...).

Setup

1. Wire your chosen breakout's SDA/SCL/VIN/GND to the board's I2C pins.
2. Install the one library from the table above that matches your sensor (you only need that one, not all three).
3. Open PinballAccelerometer/PinballAccelerometer.ino and set:

   #define IMU_SENSOR SENSOR_LSM6   // or SENSOR_ICM42688 / SENSOR_BMI270

4. Flash it, open Serial Monitor at 115200 baud, and keep the board still for the ~3 second auto-calibration on boot.
5. Nudge the cabinet left/right and forward/back while watching the TiltX/TiltY debug output. If a direction feels backwards or swapped, fix it in the sketch — no math required:

   #define ACCEL_INVERT_X 1   // flip to -1 to invert
   #define ACCEL_INVERT_Y 1   // flip to -1 to invert
   #define ACCEL_SWAP_XY  0   // set to 1 if X/Y are swapped on your mount

   This exists because the three recommended breakout boards don't all share the same physical axis orientation on their silkscreen.
6. In your pinball software, map the nudge/tilt input to this device's joystick X/Y axes.

How it works

• Tilt (atan2 of the filtered accel vector) maps the cabinet's static lean to a joystick position, with a deadzone (DEADZONE_ANGLE) so small vibration doesn't move the axis, ramping to full deflection at MAX_ANGLE.
• Nudge/shove detection watches the rate of change of acceleration (m/s³, normalized by real elapsed time so it behaves the same regardless of which sensor's data rate is in play) and briefly forces the joystick to full-scale in the shoved direction for SHOVE_DURATION ms. A cooldown (SHOVE_COOLDOWN_MS) and a "don't retrigger mid-pulse" guard keep sustained vibration (flippers, solenoids, a ball drop) from latching the joystick at max deflection instead of giving a short, VPX-friendly pulse.
• A low-pass filter (LPF_ALPHA) smooths the tilt signal; jerk detection runs on the unfiltered signal so real bumps aren't blunted.

All of the above are #define constants near the top of the sketch — tune JERK_RATE_THRESHOLD, DEADZONE_ANGLE, MAX_ANGLE, LPF_ALPHA, SHOVE_DURATION, and SHOVE_COOLDOWN_MS to taste on your own table.

If the sensor isn't detected at boot, the onboard LED blinks and the sketch keeps retrying rather than hanging forever, so a loose connector doesn't require a full power cycle once reseated.

Known limitation: one accelerometer per VPX instance

Visual Pinball X only reads nudge input from a single controller device. If your cabinet also uses a separate USB device for the plunger (or anything else with an axis), VPX may not distinguish between them correctly. The commonly used workaround is joy2key to remap/ merge inputs at the OS level — this is a VPX/input-routing limitation, not something this sketch can fix on its own.

Hardware requirements

• An ATmega32U4-based board (Leonardo, Pro Micro, etc.) — needed for native USB HID joystick support.
• One of the three accelerometers listed above.

Software requirements

• Arduino IDE
• Joystick library (Matthew Heironimus)
• The one sensor library matching your chosen chip (see table above)