In modern smartphones of the brand Xiaomi, Redmi and Poco, a complex set of microelectromechanical systems is responsible for tracking the position of the body in space. Users often look for a “fall sensor”, meaning a component that detects a sharp change in position of the device or its free fall. In fact, there is no separate sensor for the fall, this function is performed by a bundle of accelerometer and gyroscope. These microscopic elements are embedded directly in the device’s motherboard, making them physically inaccesible without fully disassembling the gadget.
Understanding how these sensors work is essential to properly diagnose problems with autorotating, pedometer or navigation. If your smartphone has stopped responding to tilts or is incorrectly determining orientation, the problem lies in the software processing of data from these modules. In rare cases, the cause is physical damage to the board after impact. Next, we will discuss in detail how this system works and where to look for settings to check it.
⚠️ Attention: Do not physically search for sensors on a disassembled case without experience.Microscopic components of the accelerometer damage soldering iron or static electricity if handled sloppyly.
The principle of operation of the accelerometer and gyroscope
The main element that users mistakenly call the drop sensor is the accelerometer. This component measures the acceleration projection, which is to say, it senses the force with which the device moves through space. When the smartphone is in a free fall, the overload on the sensor crystal drops to zero. It is this sharp jump that the system interprets as a fall. Xiaomi smartphones use highly sensitive three-axis accelerometers that can detect the slightest changes in the vector of motion.
The accelerometer is always paired with a gyroscope. If the first detects linear acceleration, the second determines the angular speed of rotation. The two sensors work together to allow MIUI or HyperOS to accurately determine the position of the phone in three-dimensional space. It's thanks to the gyroscope that games with the device's tilt control and virtual reality functions work. Without calibrating the gyroscope, the screen can turn jerks or not turn at all.
- 📱 The accelerometer records linear acceleration and moments of free fall of the device.
- 🌀 The gyroscope tracks the rotation of the smartphone around its axis and ensures smooth rotation.
- ⚙️ Data processing is carried out by a separate controller, unloading the main processor of the system.
Importantly, in some models, these two sensors are combined into a single chip, which saves space on the board. However, logically they remain independent modules. Android software takes raw data from these sensors and converts it into understandable event systems, such as "screen rotation" or "step." A failure in the transmission of data from either of these components causes the functions that depend on the position in space to cease to work correctly.
⚠️ Attention: Strong vibrations or constant impacts (for example, when working with a jackhammer or riding a motorcycle) can cause the accelerometer micromechanics to fail.
Physical location of sensors on the board
If you do decide to disassemble the device to visually inspect the board, keep in mind that motion sensors have no external appearances. They are small black squares several millimeters in size, soldered on the main board. In most Xiaomi and Poco smartphones, these components are located at the top of the motherboard, often in close proximity to the processor or communication module, this neighborhood is due to the need to minimize the length of signal paths to reduce interference.
Finding them by labeling without technical documentation is almost impossible, since component manufacturers (often Bosch, STMicroelectronics or Kionix) use different jacks. In some models of the Redmi Note series, the accelerometer can be put into a separate plume connecting the main board to the daughter, but this is more the exception than the rule.
When you change the screen or battery in service centers, there is often a risk of damage to the plumes going to the board, but the sensor chip itself is difficult to damage unless you use brute force or overheating. However, if the phone was hit hard in the area of the board, the crystal lattice inside the sensor could crack, in which case software calibration will not help, you need to replace the component or the entire board.
Software testing and diagnosis in MIUI
Before you can get the device repaired, you need to do a software diagnostic, and the MIUI and HyperOS shells have a powerful engineering menu built in to test the performance of all the sensors, and it uses a universal code to access it, so you don't have to look for hidden settings on the menu, you just use a standard call.
Enter ##6484## in the dial box. The last digit will automatically open the CIT menu. The list will show you a item that may be called “G-sensor”, “Accelerometer” or “Sensor” and the names may vary slightly depending on the firmware version and device model.
Inside the accelerometer testing section, you'll see a graph or numerical values of the X, Y, Z axes. Put the phone on a flat horizontal surface. Values should stabilize, and an axis perpendicular to the surface (usually Z) should show a value close to 9.8 or 1.0 (depending on the units of measurement), while the remaining axes should tend to zero. If the values jump or don't change when you turn the phone, the sensor is faulty or requires calibration.
Calibration of motion sensors
A common cause of malfunction is a downed calibration, which happens after a flashing, a big impact, or a software failure, and the engineering menu I talked about earlier often has a Calibration or DoCal button, and clicking on it triggers the reset process, and it's critical to keep the device completely flat.
If you can't calibrate the sensor with standard system tools, you can use third-party apps from the Google Play store. Programs like GPS Status & Toolbox or specialized accelerometer calibrators allow you to reset the data. The process usually looks like this: you put the phone on the table, press the calibration button in the application and wait for the process to be completed, which causes the system to rewrite the reference values of the zero position.
In some cases, resetting all settings to factory settings helps, which is a radical method, but it eliminates software conflicts. Before you do that, make sure you back up your data. Once reset, the phone behaves like a new one, and the sensor drivers will be reloaded without any configuration errors.
Comparison of sensors in different models
Not all Xiaomi smartphones have the same sensors. The Redmi series’ budget models often use simpler accelerometers with lower polling frequency. The Mi and Xiaomi flagship models feature premium sensors that respond instantly, especially in games and when using a navigator.
| Model of the device | Type of accelerometer | Presence of a gyroscope | Features |
|---|---|---|---|
| Xiaomi Redmi Note 10 | Bosch BMA456 | Yes (BMI160) | High accuracy, quick response |
| Poco X3 Pro | Integrated | Yes. | Optimized for gaming |
| Redmi 9A | Basic 3-axis | No (virtual) | Slow reaction, no VR |
| Xiaomi 13 Pro | Premium class | Yeah (precision) | Video stabilization, AR |
As you can see from the table, the lack of a full-fledged gyroscope in budget models can create the illusion of a malfunction of the "fall sensor": in such devices, the turn of the screen is slower, since the system relies only on the accelerometer and software algorithms, this is not a failure, but a feature of the hardware platform.
Influence of accessories and protective glasses
Rarely, external factors are the cause of sensor problems: massive metal bumpers or cases with built-in magnets (for example, for mounting in a car) can interfere. The magnetic field affects the operation of electronic components, although modern sensors have protection, strong magnets can distort the readings.
And there's thick security glasses, which don't affect the electronics, but they change the center of gravity and the inertia of the device when you move abruptly. But this is negligible for electronics. The real problem is cases that block access to the top of the body if there are additional light sensors that work in conjunction with the accelerometer for the "lift to the ear" function.
If you notice that the problems started after you installed a new case, try removing it and checking the sensors. In 90% of cases, the accessories do not affect the operation of the accelerometer, but eliminating this factor will take only a minute, a simple diagnostic step that should not be ignored.