What might be sensible for your market may not be sensible for others. For me, why would you use a AT89S52? The SiLabs parts the Erik crows about would seem sensible to me. The concept of having an external adc seems a waste these days (unless there is something specific requiring it).

MCS basic 51 tokenises the source itself - it doesn't rely on a PC to do it.


Anyway - if you think it is a good idea - go ahead and do it. You will learn something either through failure or success. Asking a diverse group such as us such a nebulous question really serves no one. Everyone and their dog are doing little cpu boards with a variety of i/o and selling it cheaply on the web - how would your board set itself aprt from these? Will it offer better value and/or features? These are the questions you must ask yourself