Xiaomi smartphone owners often face a situation where during a conversation the screen suddenly goes out and refuses to respond to touch, or, on the contrary, does not turn off when you bring the device to the ear. These processes are responsible for a small but critical component — the proximity sensor. Understanding the principle of its operation is necessary for each user, because it depends on the correct setting of the device comfort of communication.
In this article, we will discuss in detail what this means from a technical point of view, why sensor malfunctions occur and what calibration methods are offered by the MIUI and HyperOS operating system. You will learn how to programmatically correct the situation without contacting the service center.
The sensor is an optical sensor that emits invisible infrared light and analyzes its reflection from objects. If the reflected signal returns quickly, the system senses that an object (your ear or hand) is in front of the screen, and locks the display to save energy and prevent accidental cheek pressing.
Principle of operation and location of the sensor
Physically, the sensor is a tiny module that is usually hidden under the top of the screen or integrated into the display matrix itself in modern models. In older Xiaomi and Redmi devices, it could be seen as a small black dot next to a conversational speaker. The main task of the component is to transmit data about the distance to the object in centimeters to the system.
When you hold your phone to your ear while you're making a call, the sensor detects the distance reduction and sends a signal to the processor to turn off the touchscreen. This is a critical function, because without it, your cheek could deflect calls, turn on speakerphones or activate a voice assistant. Modern flagships use virtual sensor technology based on image and motion analysis algorithms.
There are several types of implementation of this technology in the Mi, Redmi and POCO lines:
- 📡 Infrared emitter: classic version with a separate window, sensitive to pollution.
- 🖥️ Screen sensor: built into the matrix, less visible, but requires calibration by software methods.
- 🤖 Algorithmic analysis: used in smartphones with a cut-out-drop shape, where there is no physical place under the sensor.
⚠️ Warning: If you use a black-framed protective glass, it can block the infrared sensor from operating, causing false positives. Make sure the cutouts on the film match the technical holes on the smartphone.
The accuracy of the work depends on the cleanliness of the top of the device, and even a thin layer of fat or dust can distort the reflection of the infrared beam, which will lead to incorrect screen operation during calls.
Why the proximity sensor is bugging Xiaomi
Problems with this component are among the most common complaints of users of the Xiaomi ecosystem, most often users are faced with the fact that the screen does not go out when you touch your head or, conversely, goes out immediately after you start a conversation, this can be caused by software failures in the shell of the MIUI, and physical factors.
One of the main reasons is that the system can "remember" the wrong distance thresholds, third-party applications that intercept sensor control, and the presence of magnetic cases that knock down readings of adjacent sensors.
The main symptoms of malfunction include:
- 📞 The screen does not turn off during the conversation and you click the reset or volume button with your cheek.
- 🌑 The display goes out immediately after dialing, not allowing you to press the speakerphone.
- 🔦 When you bring your hand to the top of the phone, the notification indicator does not light up (if it is tied to the sensor).
In some cases, the problem lies in the engineering menu itself, where the sensitivity settings are knocked down, which is common on devices that have been repaired, where the master did not perform the final calibration of the equipment.
Engineering menu and hidden settings
For deep diagnosis and customization of hidden parameters in Android, there is a special engineering code. On Xiaomi smartphones, access to it is often limited, but basic hardware tests are available through the standard application "Phone".
To get into the testing menu, open the call app and dial the combination ##6484##. If the code doesn't work, your firmware version may block this entry, and then you will have to use additional activation methods through the app. ADB Or special apps from the Play Market store. CIT (Customer Integration Test: Find the "Proximity Sensor".
Inside this section, you'll see the current sensor readings in real time, and as you close and open the top of the phone with your hand, you should see the change in values. If the numbers don't change or change randomly, it indicates a hardware malfunction or a critical driver failure.
☑️ Diagnostics in the engineering menu
It's important to understand that making changes to the engineering menu without understanding what they're meant for can lead to unstable system performance, and most of the items are factory debugging.
Calibration methods of the sensor in MIUI and HyperOS
The most effective way to fix a malfunction is to perform a software calibration. In the MIUI shells and the new HyperOS, this process is standardized, but requires care. Before starting the procedure, be sure to wipe the top of the screen with microfiber, removing all contamination.
Calibration is done via the same engineering menu ##6484##. Find the Proximity Sensor test. You will be asked to remove all objects from the screen and then close the sensor with your hand (usually a green light).
If the standard test doesn’t work, you can use Google Play’s Proximity Sensor Reset & Fix app, which automatically triggers the reset and recalibration process, which often solves the problem on the Redmi Note and POCO M series.
⚠️ Attention: During calibration, the phone should not be lying on the table. Hold the device in your hand or fasten it vertically so that the background behind the sensor is uniform and does not cause interference.
Once the procedure is complete, be sure to restart the device, and the first call after the reboot may take longer to establish the connection, as the system re-interviews all sensors.
What if calibration doesn’t help?
Influence of accessories and protective glasses
Often the problem is not with the smartphone itself, but with additional accessories. Cheap, wide-black-framed protective glass can block the range of an infrared emitter, in which case the sensor “thinks” that the object (the glass frame) is in the immediate vicinity and blocks the screen.
Dense leather or magnetic bookcases can also affect the sensor, especially if the magnetic fastener is close to the top edge. The magnetic field can (interfere) with adjacent sensors, such as a magnetometer, which indirectly affects the logic of the approach system.
To check, remove the case and unstick the protective glass (if it is cheap and with a frame), then repeat the test. If the problem disappears, the accessory is the cause, and it must be replaced with a model with the correct cutouts.
| Accessory type | Probability of problem | Decision |
|---|---|---|
| Black-framed glass | Tall. | Replacement with frameless glass |
| Magnetic case | Medium | Removal of the cover during the call |
| Hydrogel film | Low. | Checking of sticking |
| Thick silicone bumper | Medium | Cutting the bumper at the speaker |
The use of original Xiaomi accessories minimizes the risks, as they are designed with the location of all sensors of a particular model in mind.
Hardware malfunctions and repairs
If software methods, calibration and replacement of accessories did not help, there is a high probability of physical failure, the sensor plume could move away from the motherboard after a fall, or the module itself failed. In modern smartphones, the sensor is often soldered on the display plume, so replacing it requires qualification.
Signs of hardware failure include a constant burning of the notification indicator (if it is tied to the sensor) or a complete lack of response in the engineering menu for any actions, in which case disassembly of the device and multimeter diagnostics are required.
Self-repair is not recommended if you do not have experience with small electronics, as you can damage the touchscreen plume or matrix.
💡
Before going to the service, take a screenshot of the readings of the engineering menu so that the master sees that the sensor is not responding or shows incorrect data.
Replacing a component usually takes a little time and does not require flashing the device if the original part is used.
💡
If the sensor values do not change in the engineering menu when the upper part of the screen is closed by hand, the problem is hardware in nature and requires repair.