1.1 System Architecture Figure 2 shows the AFS in an automotive network structure. Figure 2. Automotive Network Structure This is a concept structure of the network connection for all components in the vehicle that are concerned in the AFS. Sensors in different positions around the vehicle are connected to BCM through the CAN or LIN bus. Front and rear chassis sensors detect the height of the vehicle and are connected through the LIN to BCM or through HS-CAN to the chassis system. In the latter case, information about the height of the vehicle is transferred to BCM through a CAN bus gateway unit. Rain sensors are usually implemented in the wiper or washer subsystem of the body or comfort system. This subsystem is then connected to an intelligent wiper controller through the LIN, and the wiper controller sends the weather condition information back to BCM through LS-CAN as the body or comfort system; or it is connected directly with the BCM through the LIN bus as shown in Figure 2. Vehicle speed sensor is usually located and connected in the power train system of a car through HS-CAN. The steering angle sensor is likely connected with the EPS, and the ESP subsystem belongs to the chassis system through HS-CAN. Here, their connections are simplified to a direct connection to BCM through HS-CAN. The AFS controller receives the significant sensor information from BCM through LS-CAN of the body system or HS-CAN of the chassis system. After processing on these sensor inputs, the AFS controller sends commands through the LIN bus to the AFS slave and the HID slave to perform the operation on both left and right headlights. Figure 3 shows the system architecture of the reference design. Figure 3. System Architecture of the Reference Design The following three modules are implemented: · Control panel (for demo) · AFS controller · AFS slave The control panel provides interface to the demonstrator/user with buttons, switches, and displays. The control panel collects the commands of input and transfers them into pseudo sensor signals. These signals are sent to the AFS controller through HS-CAN. The AFS controller acts as the central controller of the light. It receives and analyzes the sensor signals from the CAN bus, and make the judgment to determine the movement and light intensity of the headlight. The AFS controller sends commands through the LIN to the AFS slave for lamp movement and turns on and off all the lamps in the headlight. The AFS slave controls the stepper motors equipped with the headlight projector and achieves the movement of the light according to the commands sent by the AFS controller. 1.2 AFS Controller The AFS controller is the main control unit of the system. In the reference design, the AFS controller performs the following operations: · Checks and sets the operation mode of the entire system · Switches the light mode according to the vehicle speed and steering wheel position · Communicates with the host through the CAN bus · Sends commands to both the AFS slaves on the left and right headlights through the LIN bus to adjust the position of the lamp · Drives the parking light, HID, high beam, cornering light, and the turn indicator for demonstration purpose A TMS470MF03107 MCU is implemented on the AFS controller to achieve the expected performance. This MCU belongs to the TI Hercules MCU family. The TMS470M safety microcontroller family is based on the widely adopted ARM® Cortex™-M3 CPU running at 80 MHz. This family offers several flash memory and RAM options and a wide range of connectivity and control peripherals, such as CAN, LIN and high-end timer (HET) for PWM generation. Built-in safety features like CPU and RAM self-test (BIST) engines, ECC, and parity checking enable the TMS470M device to support applications that meet the IEC61508 safety standard. The TMS470M safety microcontrollers are AEC-Q100-qualified and are the correct fit for safety and transportation applications with lower performance needs. The TMS470MF03107 MCU has 256KB of code flash and 64KB of data flash for EEPROM emulation (320KB of flash in total), and a 100-pin QFP package. 1.3 AFS Slave ECE324-R123 mentions that any combination of moving the lamp or light source array can be implemented to achieve an adaptive front light. In this reference design, movement of the HID projector is used to perform the passing beam adaption. The movement of the lamp is performed by the AFS slave in the system by controlling two stepper motors equipped in the headlight. In a practical automotive system, there is one such control unit on both the right and left headlight units. An MSP430F2272 device is implemented on the AFS slave to control the stepper motors. This device is equipped with a 16-bit high-performance CPU core with 32KB of flash, which is sufficient for controlling the motor and communication with the LIN master. The MSP430F2272 device is also chosen because it is a very small 40-pin, QFN package UART module with LIN support and ultra-low power consumption.