When Xiaomi’s screen suddenly goes out and stops responding to touch during a phone call, it’s familiar to many smartphone owners: This is the routine behavior of the MIUI or HyperOS operating system, designed to prevent the cheek from accidentally pressing the reset button or speaker buttons. However, sometimes the proximity sensor works incorrectly, blocking the display too early or not turning it off at all, which creates noticeable discomfort when communicating.
Users often confuse software locking with physical sensor damage or system failure. In fact, this function is performed by a special optical or ultrasonic sensor located at the top of the case. Understanding how it works and the ability to properly adjust sensitivity allows you to fully control the process of locking the display during the call, making communication comfortable and predictable.
In this tutorial, we will take a look at how sensors work, how to manually adjust and how to fix common errors, how to force a screen to lock manually if the automation fails, and what to do if the display does not light up after the conversation is over, and this knowledge will help you avoid missed calls and accidental shutdowns of the interlocutor.
The principle of the sensor approach in smartphones Xiaomi
The main element responsible for blocking the screen is the proximity sensor. In modern Xiaomi models such as the Redmi Note or Poco F, most often a virtual sensor is used, which is emulated by software algorithms based on the data of the gyroscope and accelerometer, or an infrared sensor hidden under the display. When you bring the smartphone to the ear, the distance between the screen surface and the object is reduced, and the sensor detects a change in light or reflected signal.
When the proximity signal is received, Android instantly sends a command to turn off the touchscreen and dampen the matrix, which is a critical energy saving and safety function. If the screen remained active, the cheek could activate the voice dial, turn on the video or reset the call. However, in budget models or if there is a low-quality protective film, the sensitivity of the sensor can be impaired, leading to false positives.
It's important to understand the difference between a physical lock button and a software one. Pressing the power button locks the device completely, interrupting the incoming call or putting it in hold mode, while the proximity sensor only turns off input from the screen, leaving the connection active. That's why "sticking" the screen is perceived as a malfunction, although technically the system is doing its job, albeit with calibration errors.
Why is the sensor lying?
Sensitivity setting and calibration through the engineering menu
If the screen is locked too early or does not go out when brought to the face, you need to calibrate. There is a hidden engineering menu in the MIUI shell, accessible through a standard dialer. To enter it, you just need to enter the combination ##6484## or ##4636###, although some global firmware versions may restrict access to these codes by the manufacturer.
Once you log in, you need to find the section associated with the Proximity Sensor. In this section, you can usually find tests where the system asks you to cover the top of the phone with your hand and then remove it. If the values change correctly (from 0 to 5.0 or similar units), then (hardware) is good, and the problem lies in the software settings. If the values are static, you need to clean the top of the case from contamination.
☑️ Testing of the proximity sensor
Some versions of the firmware have automatic calibration, and you have to follow the instructions on the screen to start it: close the sensor, press the button, remove your hand, press again. This process reconfigures the sensitivity thresholds to the current environmental conditions. Once you've finished, you're advised to restart the device so that the new parameters are validated and stored in the system configuration file.
⚠️ Warning: Do not change the values in other sections of the engineering menu unless you are sure of their purpose.Resetting the settings of the radio module or display can lead to malfunctioning of the network or the appearance of artifacts on the screen.
Manually control the screen during the call
There are situations where automatic locking is not required or does not work correctly, and the user needs to force the screen to be extinguished without interrupting (conversation). On Xiaomi smartphones, there is usually no regular button "Switch off the screen" in the call interface, since this contradicts the logic of the system. However, there are workarounds that allow you to achieve the desired result.
One way is to use the Pocket Mode feature, which, however, locks the screen when removed from your pocket rather than allowing you to manually control it. A more effective method is to use third-party apps from the Google Play store that add a lock widget on top of the call interface, such utilities create a software layer that intercepts touches and quenches the display at the command of the user.
You can also use physical buttons. A brief tap of the power button while talking on most Xiaomi models doesn't reset the call, but locks the screen and puts the phone into sleep mode, continuing to transmit sound. It's a regular mechanism that allows you to "lock" the phone when you put it on the table, but you keep talking through the headset or speakerphone, saving battery power.
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Use Google Assistant or Siri to control your call if the touch screen is locked. The phrases "turn on speaker" or "complete call" work even when the display is dead.
Causes of false blocking and methods of their elimination
The most common cause of incorrect locking is a protective film or glass that covers the area of the sensor. Even if the area at the top of the screen appears clear visually, a layer of glue or thick glass can scatter infrared rays, making the system think that the phone is near the ear, in which case the screen goes out immediately after answering the call or does not light up when you remove the phone.
The second reason is system conflicts or errors in the Phone application. The accumulated cache may contain incorrect calibration data. To solve the problem, you need to clear the application data. This is done through the Settings path → Apps → All applications → Phone → Memory → Clear. This operation will reset the call settings, but will not delete contacts or call history.
The third reason is a software failure of the Android operating system itself or the MIUI shell. In rare cases, after updating the firmware, sensor drivers may not work stable, in which case a full reset (Hard Reset) helps, but this method should be resorted to only if other methods did not help, having previously saved all the important data.
| Symptoms. | Probable cause | Method of decision |
|---|---|---|
| The screen goes out immediately upon reply. | Sensor contamination or thick glass | Wipe the top of the screen, take the film |
| The screen doesn't go out in the ear. | Sensor calibration failure | Engineering menu, calibration |
| Accidental cheekstrokes | High sensitivity of touchscreen | In the pocket mode, a cover with sideways |
| Black screen after the call | Freeze the unlocking process | Reboot, clean the app cache |
The impact of accessories on the work of sensors
The use of third-party accessories is often a hidden cause of screen lock problems. Cheap black-framed security glasses can cover not only the visible part of the sensor, but also the area around it necessary to read the reading correctly. Xiaomi's system interprets the constant darkening of this area as finding the phone near the ear.
Magnetic-zip bookcases can also affect the magnetometer, which is used in conjunction with the proximity sensor to determine the position of the device in space. If the magnet in the case is too powerful or is not located well, it can interfere with the sensors, causing chaotic locking and unlocking of the screen during a conversation.
It is recommended to use original accessories or certified analogues, the design of which takes into account the location of the sensors of a particular model of Redmi or Poco. If after installing a new case or glass you notice problems with the screen, the first thing to do is remove the accessory and check the operation of the phone without it, this will help quickly localize the source of the problem.
Solving Software and Update Problems
Sometimes the problem is not hardware, but software optimization. Xiaomi smartphone owners often find that after upgrading to a new version of MIUI or HyperOS, the old calibration settings get lost, in which case the system can ignore the sensor readings or, conversely, be hypersensitive.
Check for updates for system applications. Go to the Security or Apps app, click on the profile icon or menu and select App Update. Make sure the System Framework, Google Play Services and Phone app are updated to the latest versions. Developers often release patches that fix sensor bugs in point updates.
If the problem occurs after installing a custom theme or launcher, try to return the standard design. Third-party shells may not properly handle system lock events. Switching to a standard theme "Classic" or "Standard" often returns the correct logic of the caller interface.
⚠️ Warning: Installing applications for "signal amplification" or "battery calibration" from unverified sources may disrupt system sensors. MIUI.
Additional settings and functions of MIUI
There are features in the system settings that indirectly affect locking, such as gesture control, which can conflict with attempts to swipe the screen immediately after a call. Try changing the way you navigate from gestures to the classic three buttons, which can improve screen responsiveness when the proximity sensor has just turned off the lock.
Also pay attention to the settings of special features. In the section Settings → Advanced settings → Special features check if it is included