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From: Paul E Bennett on 25 Oct 2009 12:09
Mel wrote:

> Paul E Bennett wrote:
>> Firstly, you didn't say which LCD module and EEPROM. Doing so might have
>> got a wider response already.
>
> I hate to damn a manufacturer with problems that are probably my own --
> see below.

I am sure no-one would have seen it as damning a manufacturer and one could
always add the phrase "probably my own stupidity..." within the mention.

>> Secondly, Logic Analysers are expensive to own and hire so doing the job
>> without is really a very worthwhile skill that more should learn to
>> cultivate.
>
> Funny you should say that. After my subconscious got serious about the
> problem, and I posted my request, I woke up in the night realizing that I
> was clocking the TWI interface too quickly for the LCD. This seems to
> have been true, and bringing the baud rate down to 100KHz has made the
> board beautifully stable.

So you have a visions of a solution then?

>> If these are serial devices I would expect to see the traces on a scope
>> easily enough. Have you got one that can capture a segment of data from
>> pre- trigger point to post-trigger point (Fluke and Tektronix both do a
>> suitable type). Such a scope will allow you to scroll back through the
>> problem zone to see what was happening in detail.
>
> The thing I have is a USB scope pod. It would be worth a try to drag the
> trigger point way over to the right and see if that left me with the last
> available traces. Since the problem involved intermittently locking up
> the U.I. loop, and ceasing to send or receive anything from the module,
> that ought to leave the smoking gun traces in plain view.
>
>> Also learn to instrument the code (toggle a pin with the idle task or
>> something) so that you can pick up points of failure.
>
> Alas, the hardware people didn't leave me any test points. Running that
> test would have me playing drums and pressing front-panel buttons with
> several hands while holding a scope probe point on an MCU pin with
> another. Life is never easy.

I suppose I am spoilt in that respect as I either select, build or specify
exactly what hardware and software will be put into the systems. I love
having suitable test points to monitor what is going on.

--
********************************************************************
Paul E. Bennett...............<email://Paul_E.Bennett(a)topmail.co.uk>
Forth based HIDECS Consultancy
Mob: +44 (0)7811-639972
Tel: +44 (0)1235-510979
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

From: Stef on 26 Oct 2009 05:02
In comp.arch.embedded,
Mel <mwilson(a)the-wire.com> wrote:
>
> Alas, the hardware people didn't leave me any test points. Running that
> test would have me playing drums and pressing front-panel buttons with
> several hands while holding a scope probe point on an MCU pin with another.
> Life is never easy.

Life can get a bit easier with some micro test clips, frees up at least one
hand. I have some from pomona that claim to be usable down to 0.3mm pitch
ICs. I have used those without problems on 0.5mm pitch, no experience with
0.3mm. One drawback, they ar not cheap but it saves you soldering test
wires to your micro which takes a lot of time and has a hazard of damaging
things.

--
Stef (remove caps, dashes and .invalid from e-mail address to reply by mail)

General notions are generally wrong.
-- Lady M.W. Montagu
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