[ECOS] Assabet lock-up after 30 seconds

Richard Panton rpanton@3glab.com
Fri Mar 16 09:48:00 GMT 2001

We've just investigated a nasty problem with the Assabet board that I'm
quite surprised no-one has mentioned on this list before.

    After 30 seconds of inactivity, the Assabet board appears to lock up,
failing to respond to interrupts. However, pressing the STOP button in GDB
appears to unlock the system.

    The RS232 driver on Assabet has an auto-power-down mode. So, after 30
seconds of no GDB packets being transmitted, the RS232 drivers power down.
When the next packet is sent from Assabet, the first 6 characters are
corrupted because the RS232 drivers power up VERY slowly. This means that
the GDB front-end does NOT see a valid GDB packet, and so will not send an
acknowlegment (or a NAK). The code on the Assabet board sits in a loop in
the cyg_hal_diag_mangler_gdb_putc() routine, with interrupts disabled,
waiting for the ACK (or for a CTRLC, which explains why the STOP button
unlocks the system).

Does anyone have any good ideas for a solution? The only ideas I have
about this are not what I would call good:

* There's no way of forcing the RS232 drivers to stay on that we can see.

* Having a separate thread that printf()s something every 29 seconds will
work, but that requires a KERNEL and timers in the eCos build.

* Sending 6 NUL characters before each packet would work, but would
probably screw up the GDB protocol.

* Toggling the RS232 power (to power-off, then back to auto-power-off) MAY
work, provided there's a 6 character delay before transmitting the first
character of the GDB packet. Of EVERY GDB packet....

Best Regards
Richard Panton              Systems Architect          3G Lab Ltd.
richard.panton@3glab.com    http://www.3glab.org/

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