"Shake it to respond" is an appealing interaction, but it leaves several questions open. How much movement counts? Does turning the object slowly count? Should it respond once while the user keeps moving it?
Recent interactive games such as Arduino's Reflexes Machine make physical action part of the experience. Before assigning a gesture, it helps to see what the motion channels actually report. On our bench we connected an MPU6050 module to a Raspberry Pi Pico on a GraftPort carrier and printed its readings with a MicroPython program built in BIPES.
Establish the sensor's frame of reference
The module connected over I2C0 with SDA on GPIO4 and SCL on GPIO5. The driver came from a MicroPython IMU project that provides imu and vector3d modules; both have to be installed on the board. The program printed X, Y and Z acceleration once per second.
The first triple in our log was approximately 0.108, -0.278 and 0.823 in the driver's acceleration scale. Our written notes had transcribed the first value differently. The logged numbers are the record to trust, which is a small reminder to keep raw logs rather than retyped values.
These axes belong to the mounted sensor. X is not automatically the user's left-right direction, especially once the module is rotated inside a housing. Keep a photo of the module's orientation with every data set, and watch how each channel changes under a known movement before writing any threshold.
Six channels do not mean six position coordinates
The MPU6050 combines a three-axis accelerometer and a three-axis gyroscope. Acceleration includes gravity, so a tilted sensor that is not moving still reports a changed vector. A gyroscope reports angular rate, not a static angle. Adafruit's MPU6050 overview describes those two sensing functions.
We also found a labeling slip in our own block reference: a section titled Gyro-Y showed a block that reads Gyro-X. Follow the visible block and the generated access path, not the heading. The same applies to any vendor example: check which axis the code actually reads.
Match the channel to the gesture
Different gestures call for different signals. These are candidate interpretations to test, not results:
- Slow tilt. The changing gravity components on the accelerometer may be enough.
- Quick twist. A gyroscope rate channel crossing a threshold may be more useful.
- Shake. Repeated acceleration changes over a short window may matter more than one axis crossing a fixed value.
- Tap. A short spike on acceleration, followed by quiet.
Ordinary handling produces many of the same signals: picking the object up, putting it down, carrying it. The rule has to separate the intended action from that background, and you only learn how well it does by recording both.
Turn a reading into one deliberate response
Our test stopped at channel output. To make it an interaction, the next trial should:
- Mount the sensor in the final orientation inside the real housing.
- Record several people performing the intended gesture, and the same people simply handling the object.
- Compare which channel and rule separates the two, using the recorded data rather than a guess.
- Add a rearm condition so one gesture gives one response, and decide what happens if the user keeps moving.
Thresholds tuned on one arrangement do not transfer to another. A rule that works with the module flat on a bench will change when the module is rotated, cushioned or mounted farther from the object's center. Keep each threshold tied to the mounting it was measured with.
If the gesture matters to the product, also decide what the device does when the sensor stops answering on the I2C bus. A motion interface that silently stops responding feels exactly like a gesture that was not recognized.