In-Depth Look into the Automotive Instrument Cluster Architecture

Automotive instrument clusters are a crucial component of modern vehicles, providing drivers with vital information about the vehicle's performance and status. These clusters have evolved significantly over the years, becoming increasingly complex with advancements in technology. In this article, we will delve deep into the architecture of automotive instrument clusters, exploring the hardware and software components, as well as other cluster design considerations. With various types of cluster development possible, such as segment LCD based, graphics based, or hybrid clusters, the underlying architecture remains consistent.

Instrument cluster architecture - Hardware

At the heart of every instrument cluster architecture lies a microcontroller (MCU) that is connected to various interfaces and devices. The following block diagram illustrates the hardware architecture:

The system typically operates on the 12V vehicle battery and is designed to handle input fluctuations ranging from 8V to 36V.

As the nervous system of the automobile, the CAN bus is utilized to acquire vehicle information from multiple MCUs within the vehicle.

• Digital Inputs: The instrument cluster receives digital inputs from various sources, contributing to its functionality. One crucial digital input pertains to the ignition switch state, which is identified through a 0 to 12V input. Other inputs, such as steering wheel or handlebar keys, can be used for user interaction.
• Analog Inputs: An array of analog inputs is fed into the cluster, which is then digitized using Analog-to-Digital Converters (ADCs). One example of an analog input is the fuel level sensor, typically represented as a resistance load ranging from 5 to 500 ohms. The resistance is converted to voltage, allowing for the derivation of the actual sensor value.
  
  Additionally, the outside ambient temperature (OAT) can be obtained through a 10 to 100K ohms channel, which is digitalized using ADCs. Analog inputs can also be utilized for various switches implemented as potential dividers.
  
• Digital Outputs: The instrument cluster utilizes digital outputs to drive tell tales, which are typically high-power LEDs. These LEDs are triggered based on specific events or fault conditions.
• PWM outputs: Pulse Width Modulation (PWM) outputs are crucial for controlling the brightness levels of the graphics LCD backlight, if available. PWM outputs can also be used to drive stepper motors when dedicated drivers are not available. Additionally, PWM outputs can drive buzzers or speakers with output frequencies ranging from 200 to 20 KHz, creating various sound effects.
• Pulse Inputs: Some of the cluster may utilize the pulse counter to calculate the RPM information from the encoder.
• Other interfaces: Depending on the display type, the instrument cluster can utilize either a segment driver or TFT driver interface to connect to the display. Optional touch interfaces can also be incorporated. The cluster can integrate several other peripherals, such as a rear-view camera connected through a dedicated camera input interface, accelerometers/gyro sensors, ambient light sensors, and more over I2C. Extended memory can be accessed through SPI/QSPI/SD interfaces. The inclusion of Bluetooth/BLE modules and Wi-Fi connectivity features is also possible.
  
  All interfaces must be designed to withstand high electrical fluctuations within the system.
  

Instrument cluster architecture - Software

As a mandatory system within an automobile, the cluster's software architecture should be robust and modular, ensuring reliable performance and ease of maintenance.

• Digital Inputs: The system only boots up or starts running the application if the ignition switch is on. Otherwise, the instrument cluster is powered off or put in deep sleep mode to conserve power.
• Analog Inputs: Analog-to-digital conversion poses its own set of challenges, primarily due to varying voltage references and an inherently noisy environment. To avoid adding strain on cost and power, the reference voltage is derived from the power supply instead of having a dedicated reference voltage. Consequently, complex reference re-calculation mechanisms are necessary to calculate the input voltage regardless of the current battery supply level. Suitable filter designs can eliminate noise components.
• Digital Outputs: Software logic must be implemented to toggle LEDs at specified intervals and patterns, indicating various types of faults or events.
• PWM outputs: Based on the luminous level or headlight condition, the software must control the backlight, ensuring it is switched on or set to a higher brightness level when necessary. Stepper motors, on the other hand, require post-processing by software filters and logic, such as PID (Proportional Integral and Differential), to facilitate smooth movements. PWM outputs can also be utilized to create sound effects using frequency and timing tables.

UX related cluster design considerations

In addition to the hardware and software architecture, there are several other cluster design considerations that automotive engineers must take into account. One such consideration is ergonomics. The cluster should be designed in a way that allows the driver to access and interpret information quickly and comfortably, minimizing distractions and enhancing safety.

Another crucial aspect is the customization and personalization options available to the driver. With the advent of digital displays, automotive instrument clusters can now offer customizable layouts, allowing drivers to personalize their driving experience. This includes choosing the information displayed, the color schemes, and even the overall theme of the cluster.

Furthermore, the durability and reliability of the instrument cluster are of utmost importance. It must withstand the harsh automotive environment, including temperature variations, vibrations, and electromagnetic interference. Robust materials, advanced sealing techniques, and rigorous testing ensure that the cluster operates flawlessly throughout the vehicle's lifespan.

Embien Expertise in Cluster Development

At Embien, we possess extensive expertise in the cluster development. Our team of skilled engineers and designers has a deep understanding of the instrument cluster architecture, hardware, and software components, as well as the design considerations involved. With a focus on innovation and user experience, we strive to create instrument clusters that seamlessly integrate into vehicles, provide accurate information, and enhance the driving experience. Our engineers are knowledgeable in AUTOSAR and Functional safety ensuing the cluster development is done at the best class possible. Our credentials include turnkey design and delivery of stepper-motor based, segment-lcd based, graphic LCD based and hybrid instrument clusters for both ICE and EV vehicles.

Conclusion

In conclusion, the hardware and software components, along with other design considerations, work together to create a seamless user experience. By comprehending this architecture, we can design clusters that meet specific requirements, provide accurate information, and enhance the overall driving experience.