10 steps to selecting a microcontroller

In an article in EDN, 10 things to be looked at for selecting a micro-controller were discussed. The items discussed were 

1. Looking at the interfaces you are going to require for connecting to external devices
2. Look at the software architecture
3. Select an architecture
4. Assess memory needs
5. Evaluate microcontroller and select one
6. Cost and power constraints study
7. Check availability
8. Make sure development software support is available
9. Take up testing of actual devices

This is a good check-list. But, do remember that it is an iterative process, not a sequential one. You will need to go back and forth between the steps. For example, at step 6 you find that the controller you selected at step 5 does not meet your power budget, you will need to go back and look at other alternatives as in step 5.

At step 1, the problem may look like a simple hardware issue. Not so with embedded systems. Hardware and  the external connections influence what amount of software you might need. If the connections are for USB or may be even Ethernet (communications in general) will need software support of the communications protocol stack.

Software architecture will determine if it will be able to support the processing you require, how often you need interrupts to be serviced, how complex those services are, if you need floating point support. In fat you will need to consider here if floating requirements are heavy enough to make sure floating point support is available on-chip.

You should have a fair idea of what kind of micro-controller you are going to need. Current needs, likely future needs, costs involved, software development tool available are some factors to be considered to arrive at a couple of likely candidates.Likely memory requirements and what addressable memory is available with the controller are some other considerations too. If you are trying to make a minimal hardware system, you need to look for adequate amount of on-chip memory. This assessment should include some extra resources as features always creep up and additional memory is required eventually. If planning on external memory, the hardware needed should be minimal and address logic should be simple. Often the external memory access is slower. You will need to make sure the access time will be acceptable.

Rest of the steps are quite self evident. Of these, the software support point is very crucial though.Read the EDN article here.
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