Why Xiaomi’s screen goes out during a conversation and how to fix it

The situation when during an important phone conversation suddenly goes out the display of a Xiaomi smartphone, familiar to many users. The screen stops responding to touch, and the subscriber can not complete the call or switch to speaker. This is not a defect or breakage of the device in most cases, but is a regular operation of the proximity sensor. This sensor is designed to save battery power and prevent accidental pressing of the cheek or ear during the time.

But sometimes the mechanism doesn't work properly: the screen may go out too early, not turn back on after the phone is removed, or, conversely, not respond at all to approach. Owners of devices with a MIUI shell or a new HyperOS often experience software failures in this node. Understanding the principles of this component will allow you to quickly diagnose the problem and return the phone to normal functionality.

In this detailed guide, we will examine all aspects of the sensor, how it is manually calibrated and how to fix software errors, learn how protective films or covers can affect the operation of the sensor, and what hidden settings can help in a critical situation.

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The proximity sensor is a hardware and software complex that can be reconfigured without contacting the service center.

The principle of the proximity sensor on Xiaomi smartphones

The main element responsible for screen damping is the infrared sensor located at the top of the front panel of the device. In modern models Xiaomi, Redmi and Poco, it is often hidden under the display glass or integrated into a dynamic conversational speaker. The sensor constantly emits invisible infrared radiation and analyzes the reflected signal. When an object (your ear or hand) approaches a distance of less than 2-3 centimeters, the level of the reflected signal increases, and the system receives a command to turn off the backlight and touchscreen.

The software part of the MIUI shell processes data from the sensor at a high polling rate. If the algorithms detect a sharp change in light in the sensor area, they interpret this as the beginning of a conversation. However, the sensitivity of this process can vary depending on the firmware version. Sometimes the software response threshold is set too high, which leads to false positives even with a minimum shadow above the top of the screen.

It's worth noting that an infrared emitter can be affected by external factors, such as a bright sun or a powerful artificial light source directed directly at the top of a smartphone, which can blind the sensor, and in such conditions, it stops distinguishing between reflected signals, and the screen can either stop going out completely or behave chaoticly.

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Use matte protective glass with cutouts under the speaker if you have persistent problems with the sensor on glossy films.

⚠️ Attention: Using poor-quality protective glasses with a black bezel overriding the sensor area (usually to the left or right of the speaker) is the most common cause of malfunction.

Diagnostics and testing with engineering code

Before you go to complex settings or data reset, you need to determine exactly whether the hardware module itself works. Xiaomi smartphones have a built-in engineering menu available through a special service. USSD-This method allows you to test the sensor response in real time without installing third-party software. To start the diagnosis, open the Phone app and dial the combination ##6484##.

Once you enter the code, the CIT (Customer Interactive Test) menu will open, and you will find ProxSensor or Approximation Sensor on the test list, and when you click on it, you will open a numerical and color display window, and if you close the top of the screen with your palm, the value will change, and the color of the indicator will switch (usually from white to green or red to green), which indicates the physical health of the component.

If the CIT test values do not change or the sensor shows a constant response even without overlap, the problem may be contamination or mechanical damage. It is also worth checking whether the "in pocket" mode is activated in the locking settings, which uses the same sensor to prevent accidental calls, in which case the screen may go out when the phone is in the bag, but not respond to the hand in the face.

Calibration of the sensor through the system menu

The most effective way to solve software failures is forced calibration, which “trains” the system to redefinition the boundaries between the states “near” and “far” again, which will require access to the engineering menu using code # # #6484#. Once you go to the “ProxSensor” section, you will see the “Calibration” or “Calibration” button.

The calibration process requires precise action, first you have to remove your hand from the screen and press the Pass or Start button to record the state "open." Then the system will ask you to completely close the sensor (usually require a tight finger press to the top of the screen) and press the confirmation button again. If everything goes well, you will see the message "Calibration Success".

It is important to calibrate in good light, but without direct sunlight falling on the phone. If the calibration fails the first time (the "Fail" message appears), try to wipe the top of the screen with microfiber and repeat the procedure. Sometimes it takes several on-off cycles after a successful calibration to apply the settings to all applications, including the standard "caller".

Call settings and additional functions

There are additional software filters in the MIUI shell that can conflict with the sensor, and in particular, Smart Response or Pocket Mode can intercept screen control, and you can check these settings by going to Settings → Lock and Protect → Pocket Mode. If this feature is activated, try turning it off and check the behavior of the screen during the call.

Also worth paying attention to the settings of the Phone app itself. Some firmware versions (especially Chinese or global ones with Google services) have their own points inside the Phone app that control the behavior of the screen. Go to Phone → Settings (three dots) → Incoming calls. There may be a proximity sensor switch that sometimes needs to be turned off and turned on again to restart the service.

Special attention should be paid to the function "Gestural response." If you have the phone raised to answer or the ear to answer, this can create additional interruptions in the sensor. → Passwords and security → Special features help to stabilize the screen during conversation.

Influence of accessories and external factors

Don't underestimate the impact of accessories on electronics. Cheap magnetic-clasp or thick-edged covers can create a magnetic field or physical shadow that the sensor perceives as an object approaching. If you notice that the problem occurred after buying a new case or a protective glass sticker, try removing them and running the test again.

Contamination in the area of the speaker is another common cause: Dust, skin fat or pile from your pocket can clog the sensor hole. Cleaning this area with a soft dry brush or a special sticky tape often works wonders. Don't use sharp objects or cleaning fluid to avoid damaging the speaker's mesh or the sensor itself.

Temperature also plays a role. When the body is heated (for example, while charging or playing before a bell), the sensitivity of electronic components can temporarily decrease.

Solving problems with touchscreen after a conversation

Sometimes the screen doesn't just go out, it stops responding to touches when the call is done, remaining black, which may be because the system didn't receive a signal from the sensor that the phone is away from the ear, and in this situation, a brief press of the lock button or the "complete call" button (if visible as a pop-up window) helps.

If the screen is left black and doesn't respond to anything, including the volume buttons, a forced reboot will be required. On most Xiaomi models, this is done by pressing the power button for a long time (about 10-15 seconds), in some cases, you need to press the power buttons and increase the volume simultaneously, this action is safe for data and just restarts the system.

For advanced users who own root rights or know how to work with ADB, there is a possibility to change the threshold values of the sensor through system files, but this requires deep knowledge and can lead to a loss of warranty. It is better for the average user to limit all settings to factory settings if software methods do not help.

⚠️ Note: Factory Reset will delete all your data, contacts and applications. Be sure to back up important information to the Mi Cloud cloud or computer before doing this.

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