A major emerging trend in the field of 3G mobile phones is the adoption and continuous development of application software (so-called "Apps"), which are written specifically for specific functions of mobile phones. Custom application software is developing rapidly, and many online "App Stores" have appeared for users to choose and purchase. However, application software is often developed and tested on an application platform, so it may not run optimally on other hardware / chipset platforms, or work with other service providers. The phenomenon of "white screen of death". This article will explore this problem and give some feasible solutions to restore the normal operation of the mobile phone.
"White Screen of Death" Solution
PC users already know that the way to recover from the blue screen of death is to restart the system completely. Many times, because the PC is locked, you must exit this freeze mode and then restart the power supply. In this case, if the suspicious mode or function that caused the blue screen of death is deleted, the operation can be completely restored.
However, some mobile devices now use non-repairable batteries. Although this is to obtain the necessary small form factor, but also to prevent users from installing inferior non-original batteries, to avoid the need to increase the risk of unreliable operation, but because of these mobile devices The battery is built-in and cannot be taken out at will, making it impossible for the user to reset and restart the device when the application software causes the device to malfunction. At this time, the user's choice can only be to drain the battery to a dead state, which may take several days or weeks, or return the locked device as a bad machine to the service provider for replacement.
To avoid this problem, designers can choose to install a separate high-power RESET switch in the mobile device. Normally, this switch is turned off. After being activated by the user, this switch can directly cut off the battery from all circuits. Although this is an effective solution, it is generally not recommended, because additional switches will cause a resistance voltage drop, and the introduction of high current wiring will increase the cost. In addition, there are safety issues, which must be passed in mobile devices. Some of the extra positions can be solved by using high current solutions.
The other is the software reset using the baseband processor. Restarting the baseband processor is a very effective method, but there are also bottlenecks. If the baseband system processor is forced to stop working due to malicious applications, it cannot identify other devices in the mobile device, such as the application processor. Even if the baseband processor resumes normal operation, it may still remain in a state where the baseband cannot be recognized. In this case, the system may resume working, but it is in an unpredictable state, and then the auxiliary system crashes. There is also a limitation in using the custom-designated software reset key, that is, users cannot always carry the user manual with them to view the software reset process.
Perhaps a power management IC may be a good choice for starting a system reset. PMIC has become more and more complicated. It includes digital control algorithms and power-on sequence itself. These control algorithms effectively control the power supply of many loads in the mobile phone according to the application and working mode. The main function of PMIC is to achieve more functions and extend battery life at the same time, so PMIC has been widely integrated in mobile device systems and feedback through the bus and interrupts. Due to the complexity of PMIC and reliance on interaction with the baseband application processor, the baseband processor in a crash state may lock the PMIC, and the user can no longer control it.
Autonomous system control technologies in high-reliability fields such as the medical and aviation markets are now entering the mobile device field. This type of architecture can use a semiconductor device called a reset chip to control or reset the PMIC and power supply equipment, and this device is independent of the equipment it controls. The chip usually has no feedback mechanism, so even if the microcontroller chip is in a crash state, it will not affect it. It can be activated by the user in a simple way, equivalent to removing the battery of the mobile device.
In this case, the system control chip such as the baseband and application processor, PMIC, and other control chips are powered off, and then sequentially powered up to enter predictable mode. It is important that this type of system reset is designed so that accidental activation does not occur. A typical activation solution for this function is to use a hidden key, usually a specified key is pressed for a longer time, or at the same time hold down some specified keys.
to sum up
In order to achieve reasonable user satisfaction, a risk-free "reset" mechanism needs to be developed for mobile devices. Without a reliable reset mechanism, device failures will occur frequently, user complaints will increase, and the number of repaired mobile phones will increase, resulting in financial losses.
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