ARM (or other 32 bit) MCUs in PDIP ?

I am now mostly up to speed on them; this is a very nice product.

I was worried about the comments here about using jumper wires to connect to the board, but I see they also offer boards (for the QFN parts) in which you can insert the traditional 0.1 inch pitch connector strips which makes for a robust connection to the stripboard/veroboard.

BTW, where do you buy your boards from in the UK ?

Two distributors are listed for the UK; Active Robots and Proto-Pic, neither of which appears to sell this type of board:

A question about this product is the placement of decoupling capacitors and crystal (thanks to whoever pointed this out) next to the MCU instead of on the baseboard which the adapter would plug into.

For the people here who have actually used this product, how did you solve this problem ?

Did you use the spare pads provided on the board and was this sufficiently close to the MCU manufacturer's specifications to work ok ?

Thanks,

Simon.

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Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world

It is surprising they have not added SMD decoupling pads interleaved with the 0.1" fanouts ? Their artwork would easily fit in the 45' channels.

-jg

I believe it was added to a later 4.5 revision, and to the 4.6 tree. Gcc tries to avoid adding new features in different revisions, so in the mainline gcc trees it is available from 4.6 onwards. But patches were made for the 4.5 trees, so you might find it in particular 4.5 builds (I believe the current CodeSourcery arm gcc 4.5 has it, for example).

mvh.,

David

I have used Active Robots as my source a few times over the years. Generally spoke to them on the phone, helpful bunch of folks.

Give them a ring and ask them, they also distribute Sparkfun so you avoid customs and import paperwork, if that is an issue for you.

I have used the square boards and put decouplers usually 0805 or 0603 caps on the corner SMT mounting pads, sometimes a few pullups there as well.

Generally my projects involve many clocks and often I have external oscillator solution (a few gates and quartz as not too high frequency) this works best as often same clock or subclock is needed eleswhere so instead of multiple crystals I run the buffered clocks around the board. In one case I needed one 12 MHz and two 6MHz so I created a master 12MHz oscillator at 3V3 uning picogates, fed into PLD and did divide by 2 in there and then ran 6MHz from 2 picogate buffers. The two buffers were for a 5V and 3V3 clock. A few picogates uses less space than multiple cystals.

For caps it was, not normally enough room for a crystal, so buffered clock drive was easier.

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For an example, with USB hub FTDI USB device, PLD with master 12 MHz and

20 MHz clocks, the PLD contains a frequency counter with gate timing from 20MHz clock, amongst many other things.

See

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+----------------  +----------------  +----------------

Hi, Linnix. Thanks for responding.

However, I'm a bit confused, and I suspect that (to quote an old film) "Whut we hayev heah is fail-yuh tuh c'mun'cate"... I'm just not sure how.

I'll try to add a bit more description to the two drawing above (Top and Side views). Imagine a PC board is etched leaving a set of "standard" copper pads for a (say) TSOP-8 package. Then imagine that a router (the drill kind, not the packet-shovelling kind) is then used to remove a strip down the center of that pad. The result is (vary roughly) "Y"-shaped, where the base of the "Y" is the trace leading off to other components or traces.

This should leave a "trough" that the TSOP-8 (or whatever) lead can lie in, and this will help keep the IC from moving about as much as it would on an unaltered pad.

Does that make more sense? Or have I misunderstood what you were saying? If the latter, could you explain in a bit more detail?

I agree that adding a groove in the board itself (as in the SchmartBoard "ez" process) would add even more "stability" (non-moving-ness) to the IC, but it requires an additional step in creating the board. It seems as if a slightly differently-shaped pad could accomplish much of the same purpose without that extra step, and easing the soldering effort for boards from any source with minimal redesign effort.

Frank Frank McKenney

--
  This evening they began to push the cars around to make way for
  the wrecker train.  The English soldiers turned out and so did the
  nurses and Friends.  Maran Lu got off a statement that will go
  down in history. "I hope we never have to travel by airplane like
  the Sixth Army girls," she said. "We travelled by jeep and had to
  get out and push the jeep.  We travelled by truck and pushed the
  truck, by raft and had to push the raft, by train and had to push
  the train.  I shouldn't like to have to get out and push an
  airplane!"         -- Gordon S. Seagrave / Burma Surgeon

On the board I'm looking at, the SMT pads are the same width as the leads. A routed trough that leaves any copper on the board at all will be too narrow for the lead. There isn't a lot of room to widen that pads either. (Really covet one of those AdaFruit USB microscopes right now.) Risk solder bridges or frying the infinitesimal copper strips off the board during rework. From what I've read, the current scheme of things counts on the surface tension of the melted solder to pull the part into alignment.

Mel.

One thing I haven't seen mentioned in this thread is the possibility of the CPU combining multiple narrow writes into a single wide write, or swallowing (only writing the last of) back to back writes to the same location. The compiler has no control over any of this.

Much of the discussion has been about too many (code visible) accesses. Regardless of the disassembly, the hardware actually may be doing something different. If you really need multiple writes to occur, some CPUs require a pipeline flush or write barrier occur after each write. I am not aware of any compiler that correctly handles this.

George

Many processors allow you some control over this through an MMU or similar mechanism - you can define areas that will not be cached, and for which all reads and writes are executed as originally ordered. For some cpus you may also need some sort of synchronisation or barrier instruction to enforce the order (like the PPC's "EIEIO" instruction). Compilers won't generate these automatically - you need to add them yourself where you need them, and be aware that they often cost a fair number of cycles due to pipeline flushes/stalls.

Thanks. I've been in touch with them and am waiting to hear back from them on pricing.

(And yes, customs is a major importing issue as far as I am concerned. :-))

Thanks for the detailed design notes (and thanks for the example photograph in your other posting). It helps me to understand how you are using the boards.

Thanks,

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world

Hi, Mel.

Thanks for jump> Frnak McKenney wrote:

Oh.

... "Nevermind!" (*)

This is probably what linnix was trying to tell me. (Sorry about that!)

For what it's worth, I have one of those USB 'scopes, and it takes really nice pictures, but it does have a few drawbacks for someone who wants to use it in place of an assembly/inspection microscope. First, it's hard to focus: the "knurled" focus adjustment is stiff and tends to shift the microscope while you adjust it. It's often easier to set the focus, then move the microscope around to get the view you want. Second, it's light, and unless you're extremely careful it gets bumped so the object being disappears out of frame. Hand-held pictures are not impossible, but tricky without an arm rest.

I've been meaning to build something out of an old gooseneck lamp, but haven't gotten "a round tuit" yet.

If you're curious, you can find a number of USB microscopes here:

Just do a search on... well, "usb microscope".

Frank

(*)

--
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  arrogance. It is humbling to discover how many of our glib
  assumptions, which seem to us novel and plausible, have been
  tested before, not once but many times and in innumerable guises;
  and discovered to be, at great human cost, wholly false.
                             -- Paul Johnson

It sounds like an excellent solution to a nearly-nonexistent problem.

I have no trouble soldering 0.5mm pitch parts onto bare (no solder mask) boards; while I have the advantage of an assembly microscope, even before I got it I could still get the job done with a watchmaker's loupe and some care taken.

You just tack down the corners of the chip, goober solder on all over everything without worrying about solder bridges, then use desoldering braid to remove all the bridges you just created.

That seems "schmarter" than using someone else's prototyping board, to me.

--
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While a nice binocular microscope with large field of view and focal distance, and perhaps with long and movable arm is expensive, I am using a ghetto microscope that I got on Ebay for $30. I use it for electronics and for ton of other household tasks (splinter removal and other domestic surgeries), probably at least once a week over last several years. One of the better tool investments I made.

I don't see it now for the price I got it from, but it is almost exactly like this one:

While a nice binocular microscope with large field of view and focal distance, and perhaps with long and movable arm is expensive, I am using a ghetto microscope that I got on Ebay for $30. I use it for electronics and for ton of other household tasks (splinter removal and other domestic surgeries), probably at least once a week over last several years. One of the better tool investments I made.

I don't see it now for the price I got it from, but it is almost exactly like this one: