This is merely a historical archive of years 2008-2021, before the migration to mailman3.
A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/simtrace@lists.osmocom.org/.
Harald Welte laforge at gnumonks.orgOn Sun, May 08, 2011 at 05:00:59PM +0200, Kevin Redon wrote:
> Hi
>
> The corrections have been applied. I hope I did not forget anything.
thanks a lot.
> The main changes :
> - reset is a jumper
just to be precies: it's the TEST pin, not RESET (schematics is ok!)
> - bootloader switch added
see my comment from the last mail
> - 100k resistors used (instead of 4.7k, I hope it does not break anything)
yes, it should work. and if we run into problems, it's very easy to
solder different resistors to the same footprint.
> - jack connector added (for the debug)
> - WP from flash connected
great. Does the SAM7 have an internal pull-down on nWP? If not, we
should add one, just to be sure the power-up default state is LOW.
> - USB voltage regulator TPS73633 used (lower capacitance)
Ok, let's try that one.
> - USB buffer used instead of the openPCB solution (thus no pull-up and
> reset connection). saves space and complexity
I am not familiar with USB buffers? How do they work? I couldn't find
a data sheet for USBBUF02 or USBBUF02W6. Also, I don't see how this
solves the problem, sorry.
Some more explanation:
When the AT91SAM7 is reset (software-reset or hardware-reset), it needs
to generate a USB bus reset in order to tell the host PC to
re-enumerate. This is required as the SAM7 has no information about the
USB protocol state before the ARM CPU was reset.
The other reason is: When we switch from DFU into normal mode (or the
other way around), we again need to be able to issue a USB reset from
software (via GPIO) and ask the host to re-enumerate. This is required
as we expose different interface/configuration descriptors depending on
DFU / normal mode.
So I don't really see a choice but to have a software-controlled USB
reset option. Once again, we know that this part is working in OpenPCD
0.4 (we had a couple of earlier versions, and they all had some
shortcomings). It's really useful to have both the nRESET as well as
the GPIO controlled usb-pullup (called UDP_PUP) in OpenPCD.
If we don't do this properly, we will have to disconnect/reconnect the
device from USB very often. Doing this from software is much easier and
fail-proof.
> - QS3244 instead of QS3245 used, I/O and other pins are controlled
> separately
great.
--
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)