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bug #37768 Poll usbtiny 100 times at init time to handle low-clock devices 

Add a FAQ entry describing the method to connect to a device
where the firmware has reduced the internal clock speed.


git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk@1218 81a1dc3b-b13d-400b-aceb-764788c761c2
This commit is contained in:
Joerg Wunsch 2013-09-12 11:20:03 +00:00
parent 11512d89be
commit 80cec375d5
2 changed files with 25 additions and 1 deletions
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@ -1,3 +1,9 @@
2013-09-12 Joerg Wunsch <j.gnu@uriah.heep.sax.de>
bug #37768 Poll usbtiny 100 times at init time to handle low-clock devices
* doc/avrdude.texi: Add a FAQ entry about how to connect to a
target where the firmware has reduced the internal clock speed.
2013-09-11 Joerg Wunsch <j.gnu@uriah.heep.sax.de>
bug #28344 chip_erase_delay too short for ATmega324P, 644, 644P, and 1284P

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avrdude/doc/avrdude.texi
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@ -70,7 +70,7 @@ Use @uref{http://savannah.nongnu.org/bugs/?group=avrdude} to report bugs.
Copyright @copyright{} 2003,2005 Brian S. Dean
Copyright @copyright{} 2006 - 2008 J@"org Wunsch
Copyright @copyright{} 2006 - 2013 J@"org Wunsch
@sp 2
Permission is granted to make and distribute verbatim copies of
@ -2495,6 +2495,24 @@ affected by this.
See also: @url{http://www.libusb.org/ticket/6}
@item
Problem: after flashing a firmware that reduces the target's clock
speed (e.g. through the @code{CLKPR} register), further ISP connection
attempts fail.
Solution: Even though ISP starts with pulling @var{/RESET} low, the
target continues to run at the internal clock speed as defined by the
firmware running before. Therefore, the ISP clock speed must be
reduced appropriately (to less than 1/4 of the internal clock speed)
using the -B option before the ISP initialization sequence will
succeed.
As that slows down the entire subsequent ISP session, it might make
sense to just issue a @emph{chip erase} using the slow ISP clock
(option @code{-e}), and then start a new session at higher speed.
Option @code{-D} might be used there, to prevent another unneeded
erase cycle.
@end itemize