board questions regarding MitM
ml at mail.tsaitgaist.info
Fri Aug 16 18:01:08 UTC 2013
Thanks for the info.
I did not looked into it yet, but will either try to fix it in software (the pullup is a good start) before designing the second version of SIMtrace,
or add a filter, cap, or pull-down if this is not possible.
Excerpts from Tom Schouten's message of 2013-08-16 17:38:52 +0200:
> Hi List,
> When the SIMtrace ciruit operates in MitM mode, the RST and VCC lines
> coming from the phone are very noisy from I/O line crosstalk in the flex
> I see about 2V peak-to-peak on the scope!
> I am expecting it leads to spurious reset/poweroff detections.
> It might be helpful to add a filter on the AT91 side for RST and VCC.
> Maye an R/C filter that can be enabled by an I/O pin using 0/HI-Z switching?
> Another idea is to do enable the internal AT91 pin pullups.
> Just loading RST and VCC a bit might be enough.
> ( Another alternative is to filter RST and VCC measurements in
> software. I tried this but results are not very meaningful at this
> point.. )
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