| With the rapid development of automotive electronics, new control algorithms ?the calibration data of engine and new functions are being introduced frequently in vehicle electronic control unit(ECU).Therefore, the software on ECU requires updating by frequently plugging ECU memory in the traditional way, which is not only easy to damage the circuit board, but also very inconvenient for the ECU loaded in the car. A bootloader is implanted into the flash memory of ECU for updating in many manufacturers.But the flash memory is not allowed to programming itself when the bootloader software is running on it. The bootloader is moved into RAM to run when programming the flash. This way has the following defects: First, the application may be erased exceptionally when running away, which could lead unpredictable harm; Second, the storage memory of bootloader will increase, which could limit the flash storage capacity and the flexibility of the design of application software; Third, the flash memory will be damaged if power outages happen in the process of updating. In addition, the traditional bootloader is not convenient because it takes USB-CAN adapter to update software for ECU and PC as a host widely.Considering the defects of the traditional bootloader in programming vehicle ECUs online, a two-level bootloader is presented that consists of the primary bootloader and the secondary bootloader.A smart node with the capability of two-level bootloader and its supporting software on ECU are designed based on CAN bus.When the software on ECU is updating,the node communicates with ECU by international standard CAN Calibration Protocol(CCP) and gets the secondary bootloader software.Then the secondary bootloader is loaded into the RAM memory on ECU for running and controls the ECU.And then the target software code from USB Disk or remote PC by GPRS is programmed into Flash memory on ECU.The secondary bootloader will be disappeared when the updating is finished and the application software remains only. A special schematic and its software project are presented with MC9S12G128 of Freescale for the online programming system of FAI EFI ECU.Now the system is in the production stage and has important practical value.According to the test of remote communication?flash memory updating and reliability of the system, the smart node is convenient, feasible and with high reliability as updating instrument for ECU. Moreover, defects of current software updating methods like the insecurity of application code, a high cost and requirement of more flash memory are avoided successfully and simultaneously a new method of In Application Programming(IAP) for embedded system is supplied creatively. |
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