Embedded processors for DIY projects ?

[Byron G. Jacquot]

Howdy Michael,

There are dozens of microcontrollers around...just because there are some
new ones doesn't mean that the older ones are now useless.  There are some
new variants on the 8051, Z80 and 6502 that keep those lines alive.  I've
not used any of them, so I can't really comment on that.  Instead, I'll keep
this short, and answer your questions as they apply to Atmel's AVR...my
assumption is that the latest PICs are similar.

>- Scalability (price-wise) there should be cheap units (no more than $15 a
piece) for
>  simple devices that do not need much computing power, and also faster
ones in which
>  i could reuse parts of my code for more complex/demanding applications

AVRs come in a wide variety of sizes, from 8-pins with very little ROM, to
some fairly large ones in modern hi-density packages with sometihng like 32K
bytes ROM.

The core of the machine doesn't change much...the very smallest ones have
fixed-depth hardware stacks, the larger add multiply and divide
instructions.  The mid sized ones sell for about $6 in single quantities.

At any given level, there are often a couple of variants, one reasonably
hefty, the other with a couple more peripherals and more ROM.  The middle of
the range have some parts that are well suited to DIY music making.

>- Availability of an (affordable) in-circuit single step debugging tool so
i can plug a cable
>  into my current project at the bench and measure in/out lines with the
scope while
>  tracing instructions through the code

There was (I haven't been following for a long time now) an
In-circuit-emulator for the middle of the AVR family that sold for $200.  I
haven't had the need for one, so I don't know it's current status, or it's
features.

I usually wound up with the simulator software when I had tough bugs to
crack...not as pretty as an ICE, but still free.

>- Availability of versions with 8 or 16 bits DAC´s and ADC´s

Yup.  The AVR 8535 has an 8-channel multiplexed 10-bit ADC.

I know of no processors from anyone in this arena that have DACs onboard
(Not Motorola, PIC, AVR, etc)...but there are plenty of external DACs
that'll interface using whatever method youre comfortable with.

>- EEPROM programming memory to shorten development cycles, in sizes from 2 KB
>  to (say) 8 KB, larger sizes a plus

AVRs are all in-system FLASH programmable.  The Mid-sized ones (8515 or
8535) hold 4K-8K bytes (2K-4K instructions)

>- RAM 64 to 512 Bytes

8535 has 512 bytes PAM, plus 512 of data EEPROM.

>- The development system should not cost an arm and a leg. I am looking for
a starter
>  kit in the price range of $300 max.

The ICE was $200, and the initial kit was $50...hunt for the STK200.  the
STK came with an Assembler, programming software, datasheets on CDROM, a
little carrier board that fits a fair variety of the parts, an 8515, and a
parallel port programmer.

>- a C compiler would be nice (included in the IDE, not some external
cross-compiler)

There arw a couple for AVR, but of you want an IDE version, it'll be a
commercial program...any recommendations Mr. Maddox?

If you can get by w/o the IDE requirement, there's a port of GNU C for the AVR.

>As far as i have seen, there are only AVR´s and PIC´s that would match my
criteria
>(ninus the C language)
>All other ones seem to have the old problems of being hard to get.

AVRs have been hard to get recently, too, because Atmel are very busy making
flash memory rather than microcontrollers.

>Another issue would be the availability of these MCU´s in DIP cases, so i
do not need
>to use an expensive and fiddly PLCC socket. (i do not have SMD soldering
equipment)

I've been able to get 8515s in DIP cases...in fact, I think all but the
largest ones are available in DIP.

>Often i wonder why the decent development environments are so extremely
costly. Are the
>manufacturers not interested in getting new customers for their MCU´s ?

I'm sure if you place a pre-order of 100,000 controllers, they'll be
flexible with things like that.  But most of us aren't Nokia, or Sony or...

Byron Jacquot