Please disregard previous report on noise. The signals are fine.
My scope probe handling and soldering skills are not :)
I had the probe ground connected to a 100mil header I put on BAT1 which
was badly soldered.
Taking it at or near the connector makes it all disappear.
The reset/poweroff I'm experiencing is probably still a protocol bug,
since it happens fairly predictably.
On 08/16/2013 02:01 PM, Kevin Redon wrote:
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.
Kevin
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
cable.
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.. )
Cheers,
Tom
