7 inch tft lcd multi information meter display factory

The traditional mechanical instrument lacks the ability to satisfy the market with characters of favorable compatibility, easy upgrading, and fashion. Thus the design of a TFT-LCD (thin film transistor-liquid crystal display) based automobile instrument is carried out. With a 7-inch TFT-LCD and the 32-bit microcontroller MB91F599, the instrument could process various information generated by other electronic control units (ECUs) of a vehicle and display valuable driving parameters on the 7-inch TFT-LCD. The function of aided parking is also provided by the instrument. Basic principles to be obeyed in circuits designing under on-board environment are first pointed out. Then the paper analyzes the signals processed in the automobile

instrument and gives an introduction to the sampling circuits and interfaces related to these signals. Following this is the functional categorizing of the circuit modules, such as video buffer circuit, CAN bus interface circuit, and TFT-LCD drive circuit. Additionally, the external EEPROM stores information of the vehicle for history data query, and the external FLASH enables the display of high quality figures. On the whole, the accomplished automobile instrument meets the requirements of automobile instrument markets with its characters of low cost, favorable compatibility, friendly interfaces, and easy upgrading.

As an essential human-machine interface, the automobile instrument provides the drivers with important information of the vehicle. It is supposed to process various information generated by other ECUs and display important driving parameters in time, only in which way can driving safety be secured. However, the traditional mechanical automobile instrument is incompetent to provide all important information of the vehicle. Besides, the traditional instrument meets great challenge with the development of microelectronic technology, advanced materials, and the transformation of drivers’ aesthetics [1, 2]. Moreover, the parking of the vehicle is also a problem puzzling many new drivers. Given this, traditional instruments should be upgraded in terms of driving safety, cost, and fashion.

The digital instrument has functions of vehicle information displaying, chord alarming, rear video aided parking, LED indicating, step-motor based pointing, and data storage. The instrument adopts dedicated microcontroller MB91F599, a 7-inch LCD, and two step-motors to substitute for the traditional instrument. All the information generated by other ECUs can be acquired via not only the sample circuits but also the CAN bus.

The instrument provides interfaces for different types of signals and the CAN bus. All types of signals (such as square wave signal, switching signal, resistance signal, analog voltage signal, etc.) coming from other ECUs can be acquired either from different types of sampling circuits or from the CAN bus. This makes it suitable for both the outdated application where the information from other ECUs can only be acquired via the sampling circuits and the modern application where the information from other ECUs are transmitted via the CAN bus.

The CAN bus interface and the 7-inch TFT-LCD make it more convenient to upgrade the instrument without changing the hardware. If the software needs to be upgraded, we need not bother to take the instrument down and program the MCU. Instead, we can upgrade the instrument via the vehicle’s CAN network without taking the instrument down, which makes the upgrading more convenient. Most of the information from other ECUs can be transmitted via the CAN bus; so, we do not have to change the hardware circuits if some of the ECUs’ signals are changed in different applications. Besides, since most of the driving parameters are displayed on the TFT-LCD, and the graphical user interface can be designed with great flexibility by programming, only the software needs to be revised to meet different requirements of what kind of driving parameters to display and so forth. These characters, together with the reserved interfaces, enhance the instrument’s compatibility in different applications.

It is a trend to incorporate the instrument into the vehicle information system via the CAN bus. The CAN bus interface gives the instrument access to the vehicle CAN network which enables easier fault diagnosing [3, 4] and information sharing. The fault diagnosing could be realized by accomplishing the fault diagnosing protocol above the low-speed CAN bus.

On the one hand, there are some automobile instruments which adopt 8-bit MCUs or 16-bit MCUs which have limited peripherals, so it is difficult for them to meet some requirements such as rearview video and high real-time data processing performance. And many extra components are needed if the designer wants to accomplish some functions such as video input. On the other hand, there are some advanced automobile instruments which adopt high performance MCUs (such as i.MX 53, MPC5121e, and MPC5123) and run Linux on them. They even use larger TFT-LCDs (such as the 12.3-inch TFT-LCD with a resolution of 1280 × 480 pixels) to display driving parameters. These automobile instruments show higher performances than the instrument in this paper. However, they are more expensive than this automobile. This instrument is able to provide almost all the functions of the advanced automobile instrument with a lower cost.

The instrument receives signals from other ECUs via the sampling circuits or the CAN bus interface. It can also receive commands from the driver via the button interface. The signals are then processed by the MCU, after which the MCU may send the vehicle information to the LCD or light the LEDs and so forth, according to the results. Therefore, the automobile instrument can be viewed as a carrier of the information flow. And the design of the system can be viewed from two aspects: the hardware system and the information flow based on it.

The automobile instrument receives and processes information from other ECUs such as the tachometer, the speedometer, the cooling water temperature gauge, the oil pressure gauge, and the fuel gauge. The signals coming from these ECUs are of different types, according to which different kinds of sampling circuits and interfaces should be designed. Accordingly, a classification of the input signals is first carried out, as shown in Table 1.

Respecting the above mentioned factors, we finally chose the MB91F599 produced by Fujitsu as the microcontroller. The MB91F599 is particularly well-suited for use in automotive instrument clusters using color displays to generate flexible driver interfaces. It integrates a high performance FR81S CPU core which offers the highest CPU performance level in the industry. Besides, it has a graphics display controller with strong sprite functionality, rendering engine, and external video capture capabilities. These greatly reduce the need for extra components and enhance the stability of the system. The rendering engine can operate in combination with the video capture to enable image manipulation. Overlaid graphics such as needles or parking guidelines can be rendered in conjunction with captured video, which helps to accomplish the aided parking. What is more, multiple built-in regulators and a flexible standby mode enable the MB91F599 to operate with low power consumption.

Square wave signal is the signal that comes from the tachometer. The engine speed, the velocity of the vehicle, and the mileage are proportional to the frequency of the square wave signal. However, the square wave is not “standard” because it is often corrupted by interferences. Besides, the peak voltage of the square wave is +12 V while the I/O voltage of the microcontroller is . The main task for the circuits is to remove the interferences and convert the +12 V voltage to . As shown in Figure 3, the square wave signal is input from node ②; node ① is connected to one pin of the microcontroller.

where is the engine speed, is the frequency of the square wave, and is the number of pulses generated by the tachometer in every circle of the wheel.

where is the velocity of the vehicle, is the frequency of the square wave, is the diameter of the wheel, is the reduction ratio of the main reducer, and is the number of pulses generated by the tachometer in every circle of the wheel.

Figure 6 shows RGB with sync in NTSC format. The RGB varies in a positive direction from the “black level” (0 V) to 700 mV. Meanwhile, a sync waveform of −300 mV is attached to the video signal. Since the output video signal of the camera is AC-coupled, a clamp circuit is needed to clamp the RGB and sync to a reference voltage and leave the others to vary. If not clamped, the bias voltage will vary with video content and the brightness information will be lost [5].

The video buffer circuit consists of a clamping circuit (, , ) and an emitter follower (, , ), as shown in Figure 7. Node ① is connected to the NTSC input pin of the microcontroller; node ② is connected to the clamp level output pin of the microcontroller; node ③ is connected to the camera’s signal output. is the coupling capacitor; is the matching resistor to realize the 75 Ω back termination.

Here, the sync signal is not present, so the clamp level is controlled by the clamp level output pin of the microcontroller, which is called “keyed clamp” [5]. The graphics display controller of the microcontroller let the clamp level output occur in coincidence with the sync pulse; that is, the clamp level output occurs during the sync tip in Figure 6, thus we get the “sync tip clamp” [5].

Since the FLASH size of the microcontroller is only 1 MB which is limited for the storage of pictures displayed on the LCD, external FLASH is needed to store different kinds of meaningful pictures such as the background of the dial. Two S29GL256N chips with a memory capacity of 256 Mb are chosen for picture data storage for their high performance and low power consumption. The application circuits of the chips are provided in their datasheets, so it is unnecessary to go into the details of them here.

Controller Area Network (CAN) is widely deployed in automobile, industry, and aerospace domains. As a major trend of the technological development of in the automation industry, CAN is now reputed as a local area network in automation [6]. Its low cost and ability to integrate with most microcontroller silicon families have made it a standard for automobile applications [7–9].

Full active suspension control, airbag control, traction control, and so forth are incorporated into high-speed communication system since their requirements of real-time response and reliability are critical. Because of less critical requirements, on-board fault diagnosing [17, 18], doors control, windows control, and so forth are incorporated into low-speed communication system. The transmitting rate of the high-speed CAN bus is 500 kbps while that of the low-speed one is 250 kbps. The two kinds of communication systems are connected via a gateway which enables real-time sharing of data. And the data transmitting of the high-speed CAN bus has a higher priority over the low speed CAN bus when a collision occurs.

The 7-inch TFT-LCD has a resolution of pixels and supports the 24-bit for three RGB colors. The interface of the 60-pin TFT-LCD can be categorized into data interface, control interface, bias voltage interface, and gamma correction interface.

The data interface supports the parallel data transmitting of 18-bit (6 bits per channel) for three RGB colors. Thus, a range of colors can be generated. The control interface consists of a “horizontal synchronization” which indicates the start of every scan line, a “vertical synchronization” which indicates the start of a new field, and a “pixel clock.” This part is controlled by the graphics display controller which is integrated in the MB91F599. We just need to connect the pins of the LCD to those of the microcontroller correspondingly.

Bias voltages are used to drive the liquid crystal molecules in an alternating form. The compact LCD bias IC TPS65150 provides all bias voltages required by the 7-inch TFT-LCD. The detailed circuit is also provided in the datasheet of TPS65150.

The greatest effect of gamma on the representations of colors is a change in overall brightness. Almost every LCD monitor has an intensity to voltage response curve which is not a linear function. So if the LCD receives a message that a certain pixel should have certain intensity, it will actually display a pixel which has intensity not equal to the certain one. Then the brightness of the picture will be affected. Therefore, gamma correction is needed. Several approaches to gamma correction are discussed in [20–22]. For this specific 7-inch LCD, only the producer knows the relationship between the voltage sent to the LCD and the intensity it produces. The signal can be corrected according to the datasheet of the LCD before it gets to the monitor. According to the datasheet, ten gamma correction voltages are needed. These voltages can be got from a resistive subdivision circuit.

For this instrument, the LED indicators, the backlight, and the chord alarm need to be supplied with a voltage of +12 V; the CAN transceiver, the EEPROM, and the buttons need to be supplied with a voltage of +5 V; the video buffer circuit, the external FLASH, and the data interface of the LCD need to be supplied with a voltage of +3.3 V. Besides, the microcontroller needs to be supplied with voltages of +5 V and +3.3 V simultaneously. Figure 8 offers a detailed block diagram of the power supply for the automobile instrument.

The main task for the program is to calculate the driving parameters of the vehicle and display them on the TFT-LCD. The calculation is triggered by the input signals via the sampling circuits or the CAN bus. The main program flow chart of the system is shown in Figure 10.

The design scheme of a TFT-LCD based automobile instrument is carried out form aspects of both the hardware and the main program flow chart. The MB91F599 simplifies the peripheral circuits with its rich on-chip resources and shows high performance in real-time data processing. The automobile instrument is capable of displaying the velocity of the vehicle, the engine speed, the cooling water temperature, the oil pressure, the fuel volume, the air pressure, and other information on the TFT-LCD, which contributes a lot to driving safety and satisfies drivers’ aesthetics. Besides, the rearview video makes the parking and backing easier and safer for the driver. Moreover, the CAN bus interface and TFT-LCD make it easier for the upgrading of the instrument without changing the hardware, thus saving the cost.

The authors acknowledge the support of China Postdoctoral Science Foundation Grants no. 2012M520738 and no. 2012M520739, Heilongjiang Postdoctoral Fund no. LBH-Z12092, and the support of the Polish-Norwegian Research Programme in the frame of Project Contract no. Pol-Nor/200957/47/2013.

Expectations continue to rise in the automotive industry, and automotive displays are at the center of the action. There is a stronger demand for greater convenience, safety, and comfort in today’s cars. Many consumers expect more than monochrome visuals from the driver’s seat; the crisp and clear graphics found in a TFT LCD display offers an excellent way to satisfy this need.

Drivers today are not content with using their vehicles to get from Point A to Point B anymore. That’s why modern passenger cars now have numerous cutting-edge capabilities that enhance the daily lives of car owners and passengers, such as on-road entertainment, appointment scheduling, and other connected services. A TFT LCD module is a great option for smart displays that accomplish these activities.

The current trend among OEMs is to roll out economic vehicle variants with advanced display applications. Of course, the cost of equipping a car with the latest smart displays will have quite an impact on its overall price. TFT module displays can deliver practical solutions to various automotive display applications depending on the needs of the project.

In as little as two decades ago, you’ll find instrument clusters, infotainment units, information displays, and other automotive electronics components equipped with monochrome LCD panels in their basic form. However, technological and electronic advancements have allowed for display applications to integrate more and more vehicle functions.

The past years have seen advanced display applications featuring TFT-LCD and LCD display panels. LCD panels are particularly effective for the instrument cluster, the basic center stack touchscreen, and the rear seat entertainment touchscreen. TFT LCD displays, meanwhile, were preferred for more advanced applications thanks to their appeal and visual quality. Both LCD and TFT-LCD technologies satisfy strict automotive application requirements.

Automotive display applications are home to advanced functions. Therefore, display panel manufacturers must meet the stringent requirements for durability and ideal temperature in automotive applications.

Other advanced technologies, such as AMOLED and LED, may not be well-suited for automotive display applications because typically, these options are not able to withstand the high temperatures involved in automotive applications. They also tend to be not as durable as TFT-LCD and LCD display panels for vehicles.

While LED and AMOLED technologies do offer amazing display aesthetics, TFT-LCD and LCD displays remain some of the best options for the automotive industry.

Smart displays are not the only applications that benefit from TFT-LCD and LCD technologies. Others like speedometers, satellite navigation, tachometers, backup cameras, gauge clusters, radio controls and dash controls are also undergoing dramatic innovations.

Microtips Technology USA is a leading global manufacturer of TFT-LCD and LCD displays for automotive applications. Some available key features of our displays include:

We also offer comprehensive turnkey solutions, and we can assist with all stages of your project development, including design. For the best TFT-LCD, Touch Panels, OLED LCD, Monochrome, and Custom Segment displays, contact Microtips Technology USA today!

Have you ever wonder where TFT derive from?  Why is TFT referred to as LCD?  The phenomenon started in early days, when bulky CRT displays were thing of the past and LCD was its replacement, but as time progresses, there were still room for improvement, which leads to the birth of TFT’s.

TFT is a variant of an LCD which uses thin film transistor technology to improve an image quality, while an LCD is class of displays that uses modulating properties of liquid crystals to form what we call an LCD (liquid crystals display) which in fact does not emits light directly.

Even though LCDs were very energy efficient, light weight and thin in nature, LCD were falling behind to the CRT display, which  then leads to a change in LCD manufacturing, where performance became a big problem.

For example, having a 2001 Mustang vs a 2014 Mustang, the dimensions and engine of the 2014 has been redesign for performance reasons, not mentioning user friendly, so does the LCD to TFT.

As the birth of TFT, the elements are deposited directly on the glass substrate which in fact the main reason for the switch was because TFTs are easier to produce, better performance in terms of adjusting the pixels within the display to get better quality.

LCDs became ineffective over a period of time, almost all aspect of watching a TV, playing video games or using a handheld device to surf the net became daunting, this phenomenon is known as high response time with low motion rate.

Another problem with LCD was crosstalking, in terms of pixelating, this happens when signals of adjacent pixels affects operations or gives an undesired effect to the other pixel.

As TFT’s become very popular throughout the century due to its elaborate low charge associate and outstanding response time, LCDs became a thing of the past, and TFT became the predominant technology with their wider viewing angles and better quality this technology will be around for a long time.

The traditional mechanical instrument lacks the ability to satisfy the market with characters of favorable compatibility, easy upgrading, and fashion. Thus the design of a TFT-LCD (thin film transistor-liquid crystal display) based automobile instrument is carried out. With a 7-inch TFT-LCD and the 32-bit microcontroller MB91F599, the instrument could process various information generated by other electronic control units (ECUs) of a vehicle and display valuable driving parameters on the 7-inch TFT-LCD. The function of aided parking is also provided by the instrument. Basic principles to be obeyed in circuits designing under on-board environment are first pointed out. Then the paper analyzes the signals processed in the automobile

instrument and gives an introduction to the sampling circuits and interfaces related to these signals. Following this is the functional categorizing of the circuit modules, such as video buffer circuit, CAN bus interface circuit, and TFT-LCD drive circuit. Additionally, the external EEPROM stores information of the vehicle for history data query, and the external FLASH enables the display of high quality figures. On the whole, the accomplished automobile instrument meets the requirements of automobile instrument markets with its characters of low cost, favorable compatibility, friendly interfaces, and easy upgrading.

As an essential human-machine interface, the automobile instrument provides the drivers with important information of the vehicle. It is supposed to process various information generated by other ECUs and display important driving parameters in time, only in which way can driving safety be secured. However, the traditional mechanical automobile instrument is incompetent to provide all important information of the vehicle. Besides, the traditional instrument meets great challenge with the development of microelectronic technology, advanced materials, and the transformation of drivers’ aesthetics [1, 2]. Moreover, the parking of the vehicle is also a problem puzzling many new drivers. Given this, traditional instruments should be upgraded in terms of driving safety, cost, and fashion.

The digital instrument has functions of vehicle information displaying, chord alarming, rear video aided parking, LED indicating, step-motor based pointing, and data storage. The instrument adopts dedicated microcontroller MB91F599, a 7-inch LCD, and two step-motors to substitute for the traditional instrument. All the information generated by other ECUs can be acquired via not only the sample circuits but also the CAN bus.

The instrument provides interfaces for different types of signals and the CAN bus. All types of signals (such as square wave signal, switching signal, resistance signal, analog voltage signal, etc.) coming from other ECUs can be acquired either from different types of sampling circuits or from the CAN bus. This makes it suitable for both the outdated application where the information from other ECUs can only be acquired via the sampling circuits and the modern application where the information from other ECUs are transmitted via the CAN bus.

The CAN bus interface and the 7-inch TFT-LCD make it more convenient to upgrade the instrument without changing the hardware. If the software needs to be upgraded, we need not bother to take the instrument down and program the MCU. Instead, we can upgrade the instrument via the vehicle’s CAN network without taking the instrument down, which makes the upgrading more convenient. Most of the information from other ECUs can be transmitted via the CAN bus; so, we do not have to change the hardware circuits if some of the ECUs’ signals are changed in different applications. Besides, since most of the driving parameters are displayed on the TFT-LCD, and the graphical user interface can be designed with great flexibility by programming, only the software needs to be revised to meet different requirements of what kind of driving parameters to display and so forth. These characters, together with the reserved interfaces, enhance the instrument’s compatibility in different applications.

It is a trend to incorporate the instrument into the vehicle information system via the CAN bus. The CAN bus interface gives the instrument access to the vehicle CAN network which enables easier fault diagnosing [3, 4] and information sharing. The fault diagnosing could be realized by accomplishing the fault diagnosing protocol above the low-speed CAN bus.

On the one hand, there are some automobile instruments which adopt 8-bit MCUs or 16-bit MCUs which have limited peripherals, so it is difficult for them to meet some requirements such as rearview video and high real-time data processing performance. And many extra components are needed if the designer wants to accomplish some functions such as video input. On the other hand, there are some advanced automobile instruments which adopt high performance MCUs (such as i.MX 53, MPC5121e, and MPC5123) and run Linux on them. They even use larger TFT-LCDs (such as the 12.3-inch TFT-LCD with a resolution of 1280 × 480 pixels) to display driving parameters. These automobile instruments show higher performances than the instrument in this paper. However, they are more expensive than this automobile. This instrument is able to provide almost all the functions of the advanced automobile instrument with a lower cost.

The instrument receives signals from other ECUs via the sampling circuits or the CAN bus interface. It can also receive commands from the driver via the button interface. The signals are then processed by the MCU, after which the MCU may send the vehicle information to the LCD or light the LEDs and so forth, according to the results. Therefore, the automobile instrument can be viewed as a carrier of the information flow. And the design of the system can be viewed from two aspects: the hardware system and the information flow based on it.

The automobile instrument receives and processes information from other ECUs such as the tachometer, the speedometer, the cooling water temperature gauge, the oil pressure gauge, and the fuel gauge. The signals coming from these ECUs are of different types, according to which different kinds of sampling circuits and interfaces should be designed. Accordingly, a classification of the input signals is first carried out, as shown in Table 1.

Respecting the above mentioned factors, we finally chose the MB91F599 produced by Fujitsu as the microcontroller. The MB91F599 is particularly well-suited for use in automotive instrument clusters using color displays to generate flexible driver interfaces. It integrates a high performance FR81S CPU core which offers the highest CPU performance level in the industry. Besides, it has a graphics display controller with strong sprite functionality, rendering engine, and external video capture capabilities. These greatly reduce the need for extra components and enhance the stability of the system. The rendering engine can operate in combination with the video capture to enable image manipulation. Overlaid graphics such as needles or parking guidelines can be rendered in conjunction with captured video, which helps to accomplish the aided parking. What is more, multiple built-in regulators and a flexible standby mode enable the MB91F599 to operate with low power consumption.

Square wave signal is the signal that comes from the tachometer. The engine speed, the velocity of the vehicle, and the mileage are proportional to the frequency of the square wave signal. However, the square wave is not “standard” because it is often corrupted by interferences. Besides, the peak voltage of the square wave is +12 V while the I/O voltage of the microcontroller is . The main task for the circuits is to remove the interferences and convert the +12 V voltage to . As shown in Figure 3, the square wave signal is input from node ②; node ① is connected to one pin of the microcontroller.

where is the engine speed, is the frequency of the square wave, and is the number of pulses generated by the tachometer in every circle of the wheel.

where is the velocity of the vehicle, is the frequency of the square wave, is the diameter of the wheel, is the reduction ratio of the main reducer, and is the number of pulses generated by the tachometer in every circle of the wheel.

Figure 6 shows RGB with sync in NTSC format. The RGB varies in a positive direction from the “black level” (0 V) to 700 mV. Meanwhile, a sync waveform of −300 mV is attached to the video signal. Since the output video signal of the camera is AC-coupled, a clamp circuit is needed to clamp the RGB and sync to a reference voltage and leave the others to vary. If not clamped, the bias voltage will vary with video content and the brightness information will be lost [5].

The video buffer circuit consists of a clamping circuit (, , ) and an emitter follower (, , ), as shown in Figure 7. Node ① is connected to the NTSC input pin of the microcontroller; node ② is connected to the clamp level output pin of the microcontroller; node ③ is connected to the camera’s signal output. is the coupling capacitor; is the matching resistor to realize the 75 Ω back termination.

Here, the sync signal is not present, so the clamp level is controlled by the clamp level output pin of the microcontroller, which is called “keyed clamp” [5]. The graphics display controller of the microcontroller let the clamp level output occur in coincidence with the sync pulse; that is, the clamp level output occurs during the sync tip in Figure 6, thus we get the “sync tip clamp” [5].

Since the FLASH size of the microcontroller is only 1 MB which is limited for the storage of pictures displayed on the LCD, external FLASH is needed to store different kinds of meaningful pictures such as the background of the dial. Two S29GL256N chips with a memory capacity of 256 Mb are chosen for picture data storage for their high performance and low power consumption. The application circuits of the chips are provided in their datasheets, so it is unnecessary to go into the details of them here.

Controller Area Network (CAN) is widely deployed in automobile, industry, and aerospace domains. As a major trend of the technological development of in the automation industry, CAN is now reputed as a local area network in automation [6]. Its low cost and ability to integrate with most microcontroller silicon families have made it a standard for automobile applications [7–9].

Full active suspension control, airbag control, traction control, and so forth are incorporated into high-speed communication system since their requirements of real-time response and reliability are critical. Because of less critical requirements, on-board fault diagnosing [17, 18], doors control, windows control, and so forth are incorporated into low-speed communication system. The transmitting rate of the high-speed CAN bus is 500 kbps while that of the low-speed one is 250 kbps. The two kinds of communication systems are connected via a gateway which enables real-time sharing of data. And the data transmitting of the high-speed CAN bus has a higher priority over the low speed CAN bus when a collision occurs.

The 7-inch TFT-LCD has a resolution of pixels and supports the 24-bit for three RGB colors. The interface of the 60-pin TFT-LCD can be categorized into data interface, control interface, bias voltage interface, and gamma correction interface.

The data interface supports the parallel data transmitting of 18-bit (6 bits per channel) for three RGB colors. Thus, a range of colors can be generated. The control interface consists of a “horizontal synchronization” which indicates the start of every scan line, a “vertical synchronization” which indicates the start of a new field, and a “pixel clock.” This part is controlled by the graphics display controller which is integrated in the MB91F599. We just need to connect the pins of the LCD to those of the microcontroller correspondingly.

Bias voltages are used to drive the liquid crystal molecules in an alternating form. The compact LCD bias IC TPS65150 provides all bias voltages required by the 7-inch TFT-LCD. The detailed circuit is also provided in the datasheet of TPS65150.

The greatest effect of gamma on the representations of colors is a change in overall brightness. Almost every LCD monitor has an intensity to voltage response curve which is not a linear function. So if the LCD receives a message that a certain pixel should have certain intensity, it will actually display a pixel which has intensity not equal to the certain one. Then the brightness of the picture will be affected. Therefore, gamma correction is needed. Several approaches to gamma correction are discussed in [20–22]. For this specific 7-inch LCD, only the producer knows the relationship between the voltage sent to the LCD and the intensity it produces. The signal can be corrected according to the datasheet of the LCD before it gets to the monitor. According to the datasheet, ten gamma correction voltages are needed. These voltages can be got from a resistive subdivision circuit.

For this instrument, the LED indicators, the backlight, and the chord alarm need to be supplied with a voltage of +12 V; the CAN transceiver, the EEPROM, and the buttons need to be supplied with a voltage of +5 V; the video buffer circuit, the external FLASH, and the data interface of the LCD need to be supplied with a voltage of +3.3 V. Besides, the microcontroller needs to be supplied with voltages of +5 V and +3.3 V simultaneously. Figure 8 offers a detailed block diagram of the power supply for the automobile instrument.

The main task for the program is to calculate the driving parameters of the vehicle and display them on the TFT-LCD. The calculation is triggered by the input signals via the sampling circuits or the CAN bus. The main program flow chart of the system is shown in Figure 10.

The design scheme of a TFT-LCD based automobile instrument is carried out form aspects of both the hardware and the main program flow chart. The MB91F599 simplifies the peripheral circuits with its rich on-chip resources and shows high performance in real-time data processing. The automobile instrument is capable of displaying the velocity of the vehicle, the engine speed, the cooling water temperature, the oil pressure, the fuel volume, the air pressure, and other information on the TFT-LCD, which contributes a lot to driving safety and satisfies drivers’ aesthetics. Besides, the rearview video makes the parking and backing easier and safer for the driver. Moreover, the CAN bus interface and TFT-LCD make it easier for the upgrading of the instrument without changing the hardware, thus saving the cost.

The authors acknowledge the support of China Postdoctoral Science Foundation Grants no. 2012M520738 and no. 2012M520739, Heilongjiang Postdoctoral Fund no. LBH-Z12092, and the support of the Polish-Norwegian Research Programme in the frame of Project Contract no. Pol-Nor/200957/47/2013.

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Whatever you are currently celebrating, Christmas, Hanukkah, Jul, Samhain, Festivus, or any other end-of-the-civil-year festivities, I wish you a good time! This December 25th edition of the Nextion Sunday Blog won"t be loaded with complex mathematical theory or hyper-efficient but difficult to understand code snippets. It"s about news and information. Please read below...After two theory-loaded blog posts about handling data array-like in strings (Strings, arrays, and the less known sp(lit)str(ing) function and Strings & arrays - continued) which you are highly recommended to read before continuing here, if you haven"t already, it"s big time to see how things work in practice! We"ll use a string variable as a lookup lookup table containing data of one single wave period and add this repeatedly to a waveform component until it"s full.A few weeks ago, I wrote this article about using a text variable as an array, either an array of strings or an array of numbers, using the covx conversion function in addition for the latter, to extract single elements with the help of the spstr function. It"s a convenient and almost a "one fits all" solution for most use cases and many of the demo projects or the sample code attached to the Nextion Sunday Blog articles made use of it, sometimes even without mentioning it explicitly since it"s almost self-explaining. Then, I got a message from a reader, writing: "... Why then didn"t you use it for the combined sine / cosine lookup table in the flicker free turbo gauge project?"105 editions of the Nextion Sunday blog in a little over two years - time to look back and forth at the same time. Was all the stuff I wrote about interesting for my readers? Is it possible at all to satisfy everybody - hobbyists, makers, and professionals - at the same time? Are people (re-)using the many many HMI demo projects and code snippets? Is anybody interested in the explanation of all the underlying basics like the algorithms for calculating square roots and trigonometric functions with Nextion"s purely integer based language? Are optimized code snippets which allow to save a few milliseconds here and there helpful to other developers?Looking through the different Nextion user groups on social networks, the Nextion user forum and a few not so official but Nextion related forums can be surprising. Sometimes, Nextion newbies ask questions or have issues although the required function is well (in a condensed manner for the experienced developer, I admit) documented on the Nextion Instruction Set page, accessible through the menu of this website. On top of that, there is for sure one of my more than 100 Sunday blog articles which deals not only with that function, but goes often even beyond the usual usage of it. Apparently, I should sometimes move away from always trying to push the limits and listen to the "back to the roots!" calls by my potential readers...Do you remember the (almost) full screen sized flicker free and ultra rapid gauge we designed in June? And this without using the built-in Gauge component? If not, it"s time to read this article first, to understand today"s improvements. The June 2022 version does its job perfectly, the needle movement is quick and smooth, and other components can be added close to the outer circle without flickering since there is no background which needs constantly to be redrawn. But there was a minor and only esthetic weak point: The needle was a 1px thin line, sometimes difficult to see. Thus, already a short time after publishing, some readers contacted me and asked if there were a way to make the needle thicker, at least 2 pixels.