Ten 51 MCU programming tips

    1. Do not define too many variables. The lower 128 bits are the storage area for user-defined variables (by default). You can also put variables in the upper 128 bits, but it is easy to make mistakes. Try to put as few as possible, or better not put them at all. You can view the storage of memory variables through M51. It is best not to exceed 110 bytes, otherwise the program cannot run or errors will occur.

    2. If a variable is used in multiple places, it can be defined as a global variable. For example, loop variables i and j, try to reduce parameter passing.

    3. Static variables are best placed in the program storage area and defined with code.

    4. Variables should be defined as unsigned numbers. Variables that only occupy one bit, such as flags, should be defined as bits.

    5. Subroutines should be declared in advance after the main() main program, and those placed in front do not need to be declared.

    6. If variables and subroutines are defined but not used, the system will give a warning.

    7. Although local variables and global variables have different names, they may be changed by global variables during runtime.

    8. After the program is compiled, it is possible to generate very large files. For example, the original 5k becomes 10k after compilation. This is caused by the arbitrary allocation of program space during C assembly. You can first block part of the program and compile it, then remove the block and compile it again, you can restore it, or copy it part by part to another file and compile it.

    9. If a timer is used to generate a pulse signal, when you want to remove the pulse signal, you should first turn off the timer, and then set the level to high or low as required.

    10. The "watchdog" function can be implemented using software. For example: a program takes 50ms to run a cycle, then the timer can be set to 100ms. When it exceeds 100ms, the program will reset, and the timer will be reloaded or the timer parameters will be reset at the bottom of the program cycle.