At this stage, the resolution of the 12.3 full LCD screen is: 1280x480, 1440x540, 1920x720. For automotive LCD instrument applications, is the higher the resolution, the better? Is the increase in resolution just the job and cost of changing an LCD display? Here we analyze the user requirements and design layer by layer. Speaking of the LCD display, we must not be familiar with the word "retina screen". The retina screen is a high-resolution screen with resolutions that exceed the limits of human eye recognition, and was first introduced by Apple in 2010 at the iPhone 4 conference. For mobile phones, when the display is 10-12 inches (about 25-30 cm) from the eye, the display of the LCD reaches 300 ppi (pixels per inch), and the retina cannot distinguish the pixels. This is Apple's original definition of the "Retina Screen", and the iPhone 4 screen has a pixel density of 326ppi. How is this calculated? The image above is a schematic representation of an object with a height h, imaged on the retina at a distance from the eye to d. It can be known from the triangular relationship that the resolution angles α and d, h of the eyes have the following correspondence: The minimum resolution of the human eye is about 1 centimeter (1/60°), and the domestic visual standard of 5.0 is roughly equivalent. Consider the use of the mobile phone, you can take d = 25cm. At this time, h=0.076mm, corresponding to 333ppi. This is the origin of the retina screen. Where h is the dot pitch of the LCD. By the same token, if the distance of a typical instrument is about 70cm for the application of automotive LCD instruments, h is 0.204mm. 12.3 å‹LCD Typical dot pitch is as follows: That is to say, for the 12.3 å‹ automotive LCD instrument application, at 1440x540 resolution, 5.0 eyes can no longer distinguish the points on the screen. With higher resolution, the user experience will not be better improved. The advantage of introducing a liquid crystal dashboard in a car is that it provides a more cool display. And this effect is not only a static picture, but also a dynamic graphic image transformation process. That is, an excellent LCD panel design is not only optimal in space (reasonable resolution), but also optimal in time (animated frame rate, pixel-level dynamic Shader effect rendering). Currently, the computer's display of the screen's graphics (bitmap, vector drawing, pixel fill, Shader-level pixel rendering, etc.) is essentially a modification and calculation of in-memory, point-by-point data. When the resolution is increased on a one-dimensional scale, it means that the actual processing power needs to grow in a square relationship. For example, the resolution is increased from 1280x480 to 1440x540, and the pixel size is increased by 1.26 times. From 1440x540 to 1920x720, the pixel amount is increased by 1.78 times. This means that the display of the high-resolution display (frame rate, color value, graphics anti-aliasing, etc.) is guaranteed to be the same as the low resolution. In the former, only processing power (including CPU, GPU data transfer, rendering speed, etc.) is increased by 1.26 times; while the latter requires an additional 1.78 times. This is too demanding on the performance of the entire system, which means that CPU processing power, GPU rendering speed, and system bus throughput cannot be bottlenecked. In addition, regarding the high-resolution screen point-to-point display, the UI is required to provide a higher resolution picture. An increase in elements such as images will result in an increase in the instrument interface startup time. What if I can't guarantee the above processing power? That can only reduce the display. Make the following adjustments to the details of the UI: 1. Some (or all) pictures in the UI interface use 16-bit color pictures. From 32-bit to 16-bit, performance is required to be cut in half, making up for the 1.78x increase above. The resolution is high, but the display effect is declining. 2. Use low-resolution images for stretching or interpolation to meet the requirements for startup time and display performance. This is equivalent to not playing the high score screen at all. 3, the original can be changed with transparency, now no transparency. Reduce the animation process, the smoother acceleration and deceleration process on the low-resolution screen will become only the beginning and end state, there is no animation process. For example: the door opening and closing process on the screen. 4, GPU Shader effects (such as: particle effects, light and shadow effects) as much as possible or less use. The cool effects that could have been done now have to be simplified or even cancelled. 5. Reduce (or even turn off) anti-aliasing. Significant sawtoothing will occur at the edge of the 3D model. Although the resolution is improved, it is more visually jagged. Automotive-grade LCD instruments require an operating temperature range of -40 to 80 (or 85) °C. When the ambient temperature is 85 ° C, the temperature inside the meter must be within the temperature range in which the components can operate. First, even for automotive grade LCDs, the nominal maximum operating temperature does not exceed 85 °C. Our company actually tested that at 90 °C, the samples provided by several well-known brands of LCD screen suppliers in the industry could not work. This requires that the entire LCD instrument must be designed for heat dissipation. Second, automotive-grade processors typically have a nominal maximum operating temperature of 105 °C. That is, when the ambient temperature is 85 ° C, it must be ensured that the ambient temperature of the internal processor of the instrument housing cannot exceed 105 ° C (only the temperature difference range of 20 ° C). When the processor is working, heat is inevitable, and its power consumption is proportional to the main frequency and proportional to the square of the working voltage. The current processor has a DVFS (Dynamic Voltage and Frequency Adjustment) mechanism to dynamically adjust the core operating voltage of the processor according to the current load to achieve the purpose of reducing power consumption. That is, the high main frequency corresponds to a higher core voltage increase, and the square of the operating voltage is proportional to the power consumption. As a result, the processing speed will correspond to the relationship that the power consumption exceeds the square. A preliminary estimate of typical data shows that if the processor's main frequency is 1.78 times higher, its actual power consumption will exceed 2 times. This will bring considerable difficulty to the thermal design of the entire system - having to use a larger heat sink (the overall weight of the meter increases, the impact vibration resistance of the meter is reduced), better heat dissipation materials and methods (cost increase) ), the introduction of a fan and other active cooling mechanism (the fan life in the domestic air quality is the bottleneck of the whole machine, the impact resistance of the instrument is reduced). The design of automotive-grade full LCD instrumentation is a comprehensive consideration process. In summary, we need to consider the user experience (not only the static display effect, but also the dynamic picture experience), instrument life, overall weight, machine performance, heat dissipation, shock resistance and other aspects. . The above details, interlocking, and an increase in the resolution of the LCD screen will bring various design difficulties and cost increases. I believe that with the development of TI technology, the processor process is improved (for example: 28nm or better), the problems caused by high-resolution LCD screen will be gradually solved. But the current pragmatic approach is to consider the optimal choice of each electronic component. P02 Series Push Wire Connectors
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