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. 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
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