CAN bus realizes online upgrade of distributed embedded system
Embedded systems have many advantages such as high intelligence, small size, high reliability, and strong real-time performance. They have been increasingly used in various industries such as consumer electronics, industrial control, and automotive electronics. Often a large system is composed of many small embedded systems, and they cooperate to complete various detection and control tasks through mutual communication to form a distributed embedded system. Car GPS, reversing radar, engine control, instrument panel system, etc. in the automotive electronic system, keyboard display system, motor control system in CNC machine tools, etc., are all specific applications of embedded systems. The application of many embedded systems has brought many difficulties to the software upgrade, mainly the following: 1 These systems are located in various locations of the large system, and it is more difficult to upgrade each system separately; 2 In order to meet the requirements of confidentiality and reliability, some systems have a permanent seal on the system, and only the communication and power ports are reserved, which makes it even more impossible to upgrade it separately. In response to these problems, this paper proposes a distributed embedded system upgrade scheme using CAN bus, which realizes multi-point, single-point or even whole-system upgrade. Other types of communication ports are similar. The system structure block diagram is shown in Figure 1. Figure 1 System block diagram The entire system consists of multiple independent embedded modules that perform certain functions, the CAN bus, and a control module that is used to upgrade the entire system. The control module can also be one of the functional modules. A separate bootloader is installed on each function module, which can be regarded as the bootloader of the module. The bootloader is permanently solidified in the module and is not upgraded with the program upgrade. A CAN bus communication program is embedded in the boot program. Under normal operating conditions, each functional module works in conjunction with other modules, either alone or via the CAN bus. When a software upgrade is required for a module, the system upgrade control module sends an upgrade command to the module. After receiving the command, the module jumps to the boot program and waits for the system upgrade module to send the upgrade data. Go back to the app. 2.1 Implementation Principles of Online Upgrade Adopt ST's 32-bit embedded processor STM32F103VC based on ARM Cortex-M3 core, its on-chip Flash is the main storage area. The application code is stored in flash (0x0800C3000 ~ 0x0807FFFF), and Flash is managed by Page, so Flash can be divided into several areas to use. In this system, Flash is divided into two areas, one of which is the aforementioned bootloader area and the other is the application area. The Flash partition is shown in Figure 2. After the chip is powered on, the STM32F103VC will automatically jump to the 0x08000000 address to execute the following program. The starting position of a project (that is, the address of the main function) can be set to specifically map to the address of the Flash. In the design of this system, two main functions are placed in Flash. The bootstrap program is used to upgrade the application and jump to the application after power-on, and the application completes the corresponding module function. These two areas can be mutually jumped by specific instructions and online upgrades. Tactile Feedback Membrane Switch
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