Prototyping surface mount microcontrollers

Hi,

I am currently taking an embedded systems design class, where we are
building a computer using an ARM7 microcontroller. The class used to be
based on the 8086 processor, which could easily be mounted on a breadboard
for prototyping. After switching to the ARM, it was more difficult to do
the prototyping since the AT91M42800A only comes in a 144 pin surface
mount package. A special PCB was then designed to connect the important
pins of the chip to the breadboard through a DIP package. I suppose a
schematic would be more understandable:
http://ece.wpi.edu/courses/ece3803d07/Datasheets/AT91M42800A-DIP-adapter.pdf

Now my question is, how is prototyping performed on chips like these,
where you can't directly connect a breadboard? Do they typically build the
entire system as a PCB, get it printed and then see if it works (going
through the process again if it doesn't)? Or are there any parts that
could convert between the two packaging, similar to the one above, except
more generic?

I am really curious as to how things work in the industry.

Thanks,
Berk Birand

-- 
Posted via a free Usenet account from http://www.teranews.com

On 2007-04-17, Berk Birand <dont@email.me> wrote:

> Now my question is, how is prototyping performed on chips like
> these, where you can't directly connect a breadboard? Do they
> typically build the entire system as a PCB, get it printed and
> then see if it works (going through the process again if it
> doesn't)? Or are there any parts that could convert between
> the two packaging, similar to the one above, except more
> generic?

All of the above.  Sometimes you just go ahead and layout a
board. Sometimes you buy an eval/demo board.  You can also get
generic prototypeing boards for various SMT packages.

-- 
Grant Edwards                   grante             Yow! I'm EMOTIONAL
                                  at               now because I have
                               visi.com            MERCHANDISING CLOUT!!

On Tue, 17 Apr 2007 22:09:25 +0000, Grant Edwards wrote:

> On 2007-04-17, Berk Birand <dont@email.me> wrote:
> 
>> Now my question is, how is prototyping performed on chips like
>> these, where you can't directly connect a breadboard? Do they
>> typically build the entire system as a PCB, get it printed and
>> then see if it works (going through the process again if it
>> doesn't)? Or are there any parts that could convert between
>> the two packaging, similar to the one above, except more
>> generic?
> 
> All of the above.  Sometimes you just go ahead and layout a
> board. Sometimes you buy an eval/demo board.  You can also get
> generic prototypeing boards for various SMT packages.

What Grant said.  What you do really depends on what you want out of the
process.  

If you're working with a brand new processor that you're just
not familiar with it's a good idea to get an evaluation board,
particularly if it comes from the semiconductor manufacturer and has
accompanying schematics that you can crib off of for the next phase.

If you're confident that you can get the processor up and running on your
board, and you know just exactly what you want the board to do, then
design and build a circuit board.  I've found that building a circuit
board with SMT components and generous spacing for subsequent
modifications takes me less time that trying to build a bread board.

I haven't bread boarded anything with a processor on it for years, for the
reason stated above.  If I did, it would either be a small processor and a
small circuit, or it would be a tumor attached to an eval board, and it
would only be the parts of the circuit that I wasn't sure of.

-------------------
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Depending on your budget, take a look at Bellin surface mount prototyping
boards:  http://www.beldynsys.com/

You solder your chip to the protoboard, and then plug it into your
breadboard.

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"Berk Birand" <dont@email.me> wrote in message
news:pan.2007.04.17.20.44.01.554976@email.me...
> Hi,
>
> I am currently taking an embedded systems design class, where we are
> building a computer using an ARM7 microcontroller. The class used to be
> based on the 8086 processor, which could easily be mounted on a breadboard
> for prototyping. After switching to the ARM, it was more difficult to do
> the prototyping since the AT91M42800A only comes in a 144 pin surface
> mount package. A special PCB was then designed to connect the important
> pins of the chip to the breadboard through a DIP package. I suppose a
> schematic would be more understandable:
>
http://ece.wpi.edu/courses/ece3803d07/Datasheets/AT91M42800A-DIP-adapter.pdf
>
> Now my question is, how is prototyping performed on chips like these,
> where you can't directly connect a breadboard? Do they typically build the
> entire system as a PCB, get it printed and then see if it works (going
> through the process again if it doesn't)? Or are there any parts that
> could convert between the two packaging, similar to the one above, except
> more generic?
>
> I am really curious as to how things work in the industry.
>
> Thanks,
> Berk Birand
>
> -- 
> Posted via a free Usenet account from http://www.teranews.com
>

On Tuesday, in article <132ahcla82pf0cd@corp.supernews.com>
     grante@visi.com "Grant Edwards" wrote:

>On 2007-04-17, Berk Birand <dont@email.me> wrote:
>
>> Now my question is, how is prototyping performed on chips like
>> these, where you can't directly connect a breadboard? Do they
>> typically build the entire system as a PCB, get it printed and
>> then see if it works (going through the process again if it
>> doesn't)? Or are there any parts that could convert between
>> the two packaging, similar to the one above, except more
>> generic?
>
>All of the above.  Sometimes you just go ahead and layout a
>board. Sometimes you buy an eval/demo board.  You can also get
>generic prototypeing boards for various SMT packages.

Other factors depend on if you have used that controller (family) before
as to whether you would use an eval/demo board or have some software to
start off with. You may also use eval/demo board or previous projects
to test the basics of hardware and software interfacing.

The main consideration is how many pins the conroller has, as breadboarding
something with especially over 40 pins, takes a long time and creates
a lot more possibilities of unreliability. Spending half of your time
finding why something does not work due to broken wires etc. is wasteful
of time.

Using transition boards to take SMT chips to wires or DIP style connections
even using boards like Schmart boards can help. but you still have the
potential for problems to bite you during development.

Whatever CAD package you use to make your own prototype board means that
when the first board has been made and tested you have a starting design
and layout that can be used to get fully working board. You generally
have moved some of the board development forward. Final board layout has
enough issues with position of external components and other isues, so
saving time can be useful.

A current job (no controller) had a few breadboards for a few large pin
count devices to test a few sections of the designs. However it currently
is on TWO PCBs as the amount of connections, connectors and everything else
meant it was the only way to get some form of reliability for putting the
lot together and testing it.

-- 
Paul Carpenter          | paul@pcserviceselectronics.co.uk
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