Hi Jim,
On 15.01.2015 02:35, Jim Paris wrote:
Hi Robin,
See doc/EEPROM-structure, and git commit a45ea32b4ffd. I believe the
existing code intentionally goes against what AN_121 describes, as
written in that doc.
After some investigation, I think there's a misunderstanding.
Yes, it appears as if 4 bytes after the serial number are reserved. This
means that the statement in AN121 "Start Address = the address following
the last byte of SerialNumber string." is wrong.
However, I think there's still 96 bytes of user area since it all adds
up nicely -- the 4 extra bytes appear to be aken care of arleady in the
48 word user area as stated by AN121.
There are 128 bytes of internal EEPROM in total (AN121).
The descriptive strings begin at byte 0x1C (=28) in the EEPROMs I have
at hand (both written with FTProg and ftdi_eeprom).
28 + 48*2 + 4 = 128
Also I found out about this because I wanted to reproduce an EEPROM
written originally with FT Prog using ftdi_eeprom. The strings initially
written by FT Prog (45 characters) turned out to be 1 character (2
bytes) too long for libftdi's userarea space check (which was 88 bytes =
44 words).
With "FT Prog" I can write up to 48 characters which is exactly what
AN121 states.
If "FT Prog" (which I assume is based on FTD2XX) doesn't get it right,
who does?
Either way, the _230X is decribed in its datasheet sa having an
identical EEPROM structure as the _R, so any patch that treats them
differently is probably not correct.
You mean this datasheet:
http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT230X.pdf
It does not say its EEPROM/MTP layout is identical to type-R chips.
It does say:
"The MTP memory on all FT-X devices can be programmed over USB. This
method is the same as for the EEPROM on other FTDI devices such as the
FT232R." (p.33)
It does not give any details about the EEPROM/MTP memory layout, not to
mention about the available user area space.
Perhaps the other chip's user area space checks in libftdi should also
be reviewed, based on what "FT Prog" or FT_EE_UASize() reports.
Jim
Best regards,
Robin
--
Robin Haberkorn
Developer
metraTec GmbH
Werner-Heisenberg-Str. 1
39106 Magdeburg
Germany
haberkorn@xxxxxxxxxxxx
www.metratec.com
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