[avrdude-dev] [bug #50350] EFuse high order 4 bits writes incorrectly. Fix attached.

[anonymous]

URL:
  <http://savannah.nongnu.org/bugs/?50350>

                 Summary: EFuse high order 4 bits writes incorrectly. Fix
attached.
                 Project: AVR Downloader/UploaDEr
            Submitted by: None
            Submitted on: Sat 18 Feb 2017 05:16:06 AM UTC
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Mark
        Originator Email: address@hidden
             Open/Closed: Open
                 Release: 6.3
         Discussion Lock: Any
     Programmer hardware: STK500v2
             Device type: atmega32u4

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Details:

When programming the atmega32u4(m32u4) EFuse, AVRDude trys to write the upper
4 high bits as "0". These 4 bits are unused by the uP and are to be
unprogrammed, set to "1". This causes a mismatch when read for verification
since the uP ends up allowing 2 of these bits to be programmed:IE "1 1 0 0 i i
i i".
In the avrdude.conf file under m32u4, it is set to write "x x x x i i i i". By
updating the avrdude.conf file to "1 1 1 1 i i i i", the upper 4 bits are
properly left as a "1" while the lower 4 bits are written according to user
input. This corrects the issue.

Example: writing "F3" to the EFuse returns "C3" after programming since
AVRDude trys to write "03" and the uP mistakenly accepts 2 of the upper "0"s.
After updating the avrdude.conf to default the upper 4 bits to unprogrammed
("1"), the upper 4 bits are properly left as unprogrammed (unused) and the
EFuse properly returns as "F3".



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File Attachments:


-------------------------------------------------------
Date: Sat 18 Feb 2017 05:16:06 AM UTC  Name: m32u4 EFuse write bug.JPG  Size:
42kB   By: None
See EFuse Bug Fix.JPG for change to avrdude.conf to correct the issue.
<http://savannah.nongnu.org/bugs/download.php?file_id=39782>
-------------------------------------------------------
Date: Sat 18 Feb 2017 05:16:06 AM UTC  Name: EFuse Bug Fix.JPG  Size: 33kB  
By: None
See EFuse Bug Fix.JPG for change to avrdude.conf to correct the issue.
<http://savannah.nongnu.org/bugs/download.php?file_id=39783>

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