How to avoid smartphone "white screen of death" through technical means

One of the emerging trends in the 3G mobile phone space is the adoption and growth of application software (so called "apps") that are written specifically for a particular function on a mobile phone. Custom applications are growing rapidly and there are now many online "app stores" for users to choose from and purchase. However, applications are often developed and tested on a specific application platform and may not run optimally on other hardware/chipset platforms or with other service providers, which can result in what is commonly referred to as the "white screen of death". This article will explore this issue and provide some possible solutions to restore normal operation of the mobile phone.

Current Status and Development Challenges of Smartphones

Today’s smartphones have indeed evolved from simple talking devices to multimedia devices that can play audio /video, play games, send text messages, make phone calls, and provide comprehensive web access, allowing users to conduct banking transactions and even buy and sell on eBay. This revolution is well underway and its popularity among the general public is increasing. This trend is global, and more and more people are using mobile device applications that are completely customized for users. These customized applications can vary by region, culture, age and even gender. The expansion of applications has made mobile devices an indispensable part of people’s daily lives. People can be seen checking emails, stock market quotes, or shopping online on their mobile devices, getting instant updates on personal and business related information, etc. These applications allow people to make better use of and allocate their time.

The mobile device market consists of three major vertically integrated segments, namely service providers, handset manufacturers, and key chipset suppliers.

Of these three parts, the highest level is the service provider. The service provider allows mobile devices to connect to local base stations and then enter the network. The service provider contracts directly with mobile device users and offers a variety of different plans and service contracts. It has a variety of basic technologies inside, such as GSM and CDMA. There are huge differences between these technologies, and it has taken years of software development and evolution to achieve interoperability at the network level. There are currently dozens of service providers around the world.

The middle level is the handset manufacturer. The handset manufacturer designs and manufactures the handsets for the service providers. A GSM phone operates on a very different frequency and modulation scheme than a CDMA phone, which means the antenna, basic chipset, and software that supports the chipset are different. Handset manufacturers often launch several levels of devices at the same time. For example, high-end smartphones integrate rich multimedia features, all connected via USB ports, and have voice command capabilities. Some even use multiple microprocessors and high-speed USB connectivity to achieve simple medical diagnostic functions; mid-range smartphones have basic Internet connectivity and use a SoC microcontroller to achieve text messaging and basic calling functions; low-end phones often only provide calling functions and use ultra-low-cost basic microprocessors . In addition, software is customer-centric, and service providers of different brands require different customized software.

There are many mobile phone manufacturers around the world that make high-end, mid-range and low-end mobile phones of different types, including long-established companies and emerging startups. Many manufacturers are working hard to provide customized products for specific regions, further promoting the development of customized software.

Key chipsets are at the heart of every mobile phone, and these chipsets are generally selected based on the level of the phone. High-end smartphones may have an application processor, a baseband processor, and a power management device (PM IC ), where the application processor and baseband processor may come from the same supplier. These complex chips work in conjunction with memory, WiFi modules, USB switching mechanisms, and touch screen controllers, and are controlled by different software layers. There are currently dozens of chipset suppliers around the world, and they customize related chips for mobile phone manufacturers based on the requirements of service providers.

Since there are many service providers, mobile phone manufacturers and chip suppliers in the industry, it is very important to make application software compatible on different platforms. For example, if a consumer wants to buy a mobile phone with a pedometer application software, although he will face the choice of multiple mobile phones and multiple service providers, the key is to meet his support for the pedometer application software.

Since most applications are developed after the hardware platform is available, the application requirements are not necessarily included in the chipset/phone development verification. Although manufacturers should complete the verification process before the application is released, the huge market pressure and the lack of recognized application verification standards may lead to unverified products being rushed to market. This means that the first time a consumer uses an application on a certain set of hardware (phone and chipset)/software and network environment is likely to be the first "test run" of the application in this environment. The consumer then becomes a test product, and the test sometimes fails.

When an application runs for the first time on a platform, it has the potential to freeze the entire operation completely. Consumers use the term "blue screen of death" to describe a personal computer (PC) going out of control or freezing its operation, and a similar phenomenon is now common in the mobile industry, known as the "white screen," where the screen turns white when running an application. The "white screen" phenomenon on mobile devices is becoming more and more common, and the real cause can reportedly be traced back to the service provider. The problem that has plagued the PC industry for years is now beginning to spread to the mobile field.

Solutions for "White Screen of Death"

PC users already know that the way to recover from a Blue Screen of Death is to completely reboot the system. Many times, because the PC is locked up, it is necessary to exit this frozen mode and then restart the power . In this case, if the suspicious mode or function that caused the Blue Screen of Death is removed, a complete recovery of operations is possible.

However, some mobile devices today use non-repairable batteries. Although this is done to achieve the necessary small form factor and to prevent users from installing inferior non-original batteries and increasing the risk of unreliable operation, the batteries of these mobile devices are built-in and cannot be removed at will, making it impossible for users to reset and restart the device when the application software causes the device to fail. At this time, the user's only choice is to let the battery drain to a dead state, which may take days or weeks, or return the locked device to the service provider as a bad machine and request a replacement.

To avoid this problem, designers can choose to install a separate high- power RESET switch in the mobile device that is normally off and, when activated by the user, directly disconnects the battery from all circuits. Although this is an effective solution, it is generally not chosen because of the resistive voltage drop caused by the additional switch, the increased cost of introducing high-current wiring, and safety issues that must be addressed by using a high-current solution at some additional location within the mobile device.

Another method is to use software reset of the baseband processor. Restarting the baseband processor is an effective method, but it also has bottlenecks. If the baseband system processor is forced to stop working due to malicious applications, it will not be able to recognize 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 that the baseband cannot recognize. In this case, the system may resume operation, but in an unpredictable state, and then the auxiliary system will crash. There are also limitations to using a custom designated software reset button, that is, users cannot always carry a user manual with them to view the software reset process.

Perhaps a power management IC might be a good choice to initiate a system reset. PMICs have become increasingly complex, and include digital control algorithms and power-up sequences that effectively control the power supply to many loads in a mobile phone based on the application and operating mode. The main role of PMICs is to enable more functions while extending battery life, so PMICs have been widely integrated into mobile device systems and provide feedback through buses and interrupts. Due to the complexity of PMICs and their reliance on interaction with the baseband application processor, a crashed baseband processor may lock up the PMIC, and the user can no longer control it.

Autonomous system control technology from high-reliability markets such as medical and aviation markets is now beginning to find its way into mobile devices. Such architectures use a semiconductor device called a reset chip to control or reset the PMIC and power devices independently of the device it controls. This chip typically has no feedback mechanism, so it has no effect on the microcontroller chip even if it crashes. It can be activated by the user in a simple way, equivalent to removing the battery from a mobile device.

In this case, the system control chips such as baseband and application processors, PMIC and other control chips are powered off and then powered up in a predictable mode in a normal sequence. It is important that such system resets are designed in such a way that accidental activation does not occur. The typical activation implementation of this function is to use a hidden key, usually a designated key is pressed for a longer time, or some designated keys are pressed at the same time.

Summarize

As mobile device applications evolve, mobile phones will become more and more complex. Coupled with the fact that the application development process lags behind chipsets, mobile devices, and service providers, this means that application verification may only be performed on a specific platform or platform group. With a large camp of chipset and mobile device suppliers and service providers, there will always be some applications that have not been verified on their platforms, which increases the commercial risk of components within mobile systems and the risk to users. 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, and more and more user complaints will lead to an increase in the number of returned mobile phones, which will ultimately cause financial losses.