Re: [oopic] Re: DDELink bug and linking 2 Oopic Rs

I don't have an OOBoard - Does anyone out there use an OOBoard and
oDDELink? This would be a GREAT test.

DLC

dan michaels wrote:
> --- In oopic@yahoogroups.com, ooPIC Tech Support <dennis.clark@...>
> wrote:
>
>>One other thing - The problem does not exist when using ooPIC II+
>
> chips,
>
>>ooPIC II or any other ooPIC version on ooPIC S boards. It ONLY
>
> happens
>
>>when using an ooPIC R or ooPIC C, which use the QFP packages, and
>
> are
>
>>16F877a chips.
>>
>>DLC
>>
>
>
>
> Well, that is interesting. I think the OOBoard also uses the smt
> parts. Do you know if it also has the problem?
>
>
>
>
>
>>dan michaels wrote:
>>
>>>--- In oopic@yahoogroups.com, ooPIC Tech Support <dennis.clark@>
>>>wrote:
>>>
>>>
>>>>I've played with this problem for off and on for a while it seems
>>>
>>>and
>>>
>>>
>>>>can't find any good explanation or reasoning. You should be
>
> using
>
>>>2.7K
>>>
>>>
>>>>to 4.7K for even short distances (measured in single digit
>>>
>>>centimeters)
>>>
>>>
>>>>but it simply won't work between any two ooPICs that use the
>>>
>>>16F877a
>>>
>>>
>>>>processor and I just don't understand why.
>>>
>>>
>>>
>>>
>>>I've never played with DDE, but this large resistor value
>
> business
>
>>>makes no sense, as the 877(A) pins can all source and sink
>
> upwards to
>
>>>20-mA. 5v/20mA = 250 ohms!
>>>
>>>I wonder if there isn't some problem with the code on the newer
>>>firmware not switching modes properly between output and input,
>
> ie
>
>>>some timing issue, when the data transfers switch direction.
>>>
>>>JFTHOI, you might try putting a small series R in the leads
>
> between
>
>>>the 2 OOPic 2+ chips and see if that helps. Just a shot in the
>
> dark.
>
>>>
>>>
>>>
>>>Putting an ooPIC S board in
>>>
>>>
>>>>the circuit fixes it, so that left out cable length, noise in the
>>>
>>>wires
>>>
>>>
>>>>or just bad connectors. If anyone can figure out why this
>
> happens
>
>>>I
>>>
>>>
>>>>offer up a 4 pack of Guiness Draught cans as a prize!
>>>>
>>>>DLC
>>>>
>>>>rtstofer wrote:
>>>>
>>>>
>>>>>--- In oopic@yahoogroups.com, ooPIC Tech Support <dennis.clark@>
>>>
>>>wrote:
>>>
>>>
>>>>>>The most certain way to make sure that the DDE link works is to
>>>
>>>have an
>>>
>>>
>>>>>>ooPIC S in the loop. Otherwise the high value data and clock
>>>
>>>resistors
>>>
>>>
>>>>>>need to be used. No one can explain this oddity, but it has
>>>
>>>something
>>>
>>>
>>>>>>to do with the PIC 16F877a part.
>>>>>>
>>>>>>DLC
>>>>>
>>>>>
>>>>>If you have to use 22k to 33k resistors, the cable length
>
> between
>
>>>the
>>>
>>>
>>>>>OOPics will have to be measured in small numbers of inches.
>
> That
>
>>>much
>>>
>>>
>>>>>resistance just won't overcome any kind of capacitance.
>>>>>
>>>>>A conventional I2C network would have resistors in the 2.2k
>
> range.
>
>>>>>Unfortunately, I only have a couple of S boards so I can't
>
> really
>
>>>test
>>>
>>>
>>>>>the bug to see what is happening.
>>>>>
>>>>>Richard
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>Yahoo! Groups Links
>>>>>
>>>>>
>>>>>
>>>>
>>>>--
>>>>------------------------------------------------------
>>>>Dennis Clark ooPIC Tech Support
>>>>www.oopic.com
>>>>------------------------------------------------------
>>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>Yahoo! Groups Links
>>>
>>>
>>>
>>
>>--
>>------------------------------------------------------
>>Dennis Clark ooPIC Tech Support
>>www.oopic.com
>>------------------------------------------------------
>>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>

--
------------------------------------------------------
Dennis Clark ooPIC Tech Support
www.oopic.com
------------------------------------------------------

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