Bootloader Startup and commissioning technology of-linux system in embedded studio of the letter Chamber

In the process of building the embedded system, the first step for the construction engineer of the system platform is usually the transplant bootloader, of course, there are several levels of migration, usually the most common is the reference EVM hardware has been modified (such as changed flash, changed SDRAM, DDR SDRAM, etc.), And is the first debugging hardware, the greater difficulty is that the company is not planning to buy tens of thousands of EVM Development Board, or EVM Development Board need license to buy, then transplant bootloader is more difficult to do, but there is no way, the most effective there are two--lighting and serial printing. (This method is used by the author to debug a successful IXP2400 (XScale) redboot, EP9307 (ARM9) u-boot, etc.).

Bootloader Debugging technology-lighting , when burning write good Bootloader, start Bootloader, must be from a fixed address to start the program, the initial program is read from flash execution, some processors are directly using Flash address, Some will be alluding to the flash address, at this time SDRAM can be considered useless, how to confirm that the program is not directly executed, usually with the lighting to verify, in the bootloader entrance code snippet as far as possible before the early addition of lighting code (using Gpio control), tracking code execution, if you confirm the lighting code is not a problem, Program did not execute, that may be the start address does not point to the flash address, hardware crystal vibration does not start the vibration, hardware IC power supply problems, hardware IC pin grounding problem, CPU configuration word problems (such as the start mode), CPLD timing adjustment problems, and so on, which requires hardware and software engineers joint debugging (this requires team spirit). Of course, it would be nice if the engineer who transplanted bootloader had done the hardware. After all the problems are solved, it is inevitable that the lighting will be successful.

Bootloader Debugging technology-serial printing , after the successful lighting can be important configuration parameters tracking debugging, it is important that the program jumps to the SDRAM execution (the key is the SDRAM timing parameters and the CLK configuration is correct), and then need to get through the serial port, to open the serial port need to u The ART parameters are properly configured, the test output character function (here can not be used in the printf () function), usually after the successful illumination of the serial port is relatively easy, the focus here is to use the serial debugging program, in printf () function is available before using the low-level serial output function to implement the program's Trace debugging (usually debug assembly code), after the printf () function is available, use printf () to debug code.

As above is the bootloader debugging process of the most important two debugging technology, flexible use will bring productivity improvements, whether it is U-boot, redboot or vendor-specific bootloader (such as rrload, Vivi, etc.), two debugging techniques are effective.

(author Feng Qinghua embedded Studio-supervisor)
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Bootloader Startup and commissioning technology of-linux system in embedded studio of the letter Chamber