hi all gurus, I have a doubt about how one chooses a microcontroller for a particular project.
Say i am designing a embedded wireless system. i have my specs of the protocol which works at a particular rate. say it is a low data rate network protocol.
Say i implement the code for the stack. Now i need to decide on a microcontroller for the project. How do i look into the timing constaints. Say i mean how do i decide if i need a general CISC microcontroller, or should i need a RISC or a AVR RISC controller. On what basis do i decide the above.
As far as timing goes, do a rough estimate of the instruction rate required for the project. Use an average instructions/second value for possible configurations to see if each is obviously adequate, possibly adequate, or obviously inadequate. Discard the obviously inadequate choices.
Among the remaining candidates, you probably want to look at other parameters, such as built-in peripherals, built-in memory, cost, ease of development, etc. Rank the candidates. If any of the possibly adequate solutions are in serious contention, do a further evaluation of them, probably by coding a critical timing section to get a better estimate. Good design practice would be to allow a margin for unanticipated code or future additions. I would like to see at least 20% margin, but normally 50% or more. Bear in mind that the closer you get to a resource limit (timing, RAM space, code space, etc.), the more overhead is spent coping with that limit. I could tell stories...
You may need to evaluate memory space in the same manner.
In general, if your application is not critically cost sensitive, it is better to choose obviously adequate solutions for ease and speed of development. Remember that if this is a commercial project and it becomes successful, you may be maintaining and enhancing it for a long time. Plan accordingly.
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