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expansion board identification

Peter A. Bigot
Though I don't see it in any printable documentation, the u-boot source
for the Overo boards indicates a AT24C01B serial EEPROM is normally
installed on I2C2 at address 0x51 to provide information about the
expansion board.

The Tobi I have has this EEPROM and it is erased.

The Summit I have does not have this EEPROM (or it is unresponsive),
though the u-boot sources assign the Summit an ID number.

The Alto35 I have has the EEPROM and its contents are not consistent
with the usage documented in the u-boot machine file.

It would be nice if this feature could be used to determine which GPIOs
should be configured for which function (LED, button, etc). If the
contents from the factory can't be relied upon, then I'd at least like
to be able to use it for other purposes.

If you have a Summit, Tobi, or other board could you run these commands
from within u-boot and let me know what comes out? Here's what I see on
the Alto35:

Overo # i2c dev 2
Setting bus to 2
Overo # i2c probe
Valid chip addresses: 1D 51
Overo # i2c md 51 0 80
0000: 01 23 45 67 89 ab cd ef ff ff ff ff ff ff ff ff .#Eg............
0010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0020: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0040: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0050: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0060: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0070: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................

Thanks.

Peter


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Re: expansion board identification

Scott Ellis
An R3564 Tobi

Overo # i2c dev 2
Setting bus to 2
Overo # i2c probe
Valid chip addresses: 51
Overo # i2c md 51 0 80
0000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0020: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0030: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0040: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0050: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0060: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
0070: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
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Re: expansion board identification

Andy Walls
In reply to this post by Peter A. Bigot


On Tue, 2013-08-27 at 04:40 -0500, Peter A. Bigot wrote:
> Though I don't see it in any printable documentation, the u-boot source
> for the Overo boards indicates a AT24C01B serial EEPROM is normally
> installed on I2C2 at address 0x51 to provide information about the
> expansion board.
>
> The Tobi I have has this EEPROM and it is erased.

All of my Tobi's came with the EEPROM unprogrammed/erased.

Gumstix has a script to provision them:

meta-gumstix-extras/recipes-core/i2c-tools/omap3-writeprom/writeprom.sh



> It would be nice if this feature could be used to determine which GPIOs
> should be configured for which function (LED, button, etc). If the
> contents from the factory can't be relied upon, then I'd at least like
> to be able to use it for other purposes.

The defacto format of the EEPROM is documented here:

http://elinux.org/BeagleBoardPinMux#Expansion_boards

U-boot for the Overo looks for more than that - 94 bytes max - but
leaves about 162 bytes for whatever you want.


On a related note, on TV capture cards with EEPROMs, I observe vendors
using a tag-length-value format to encode information in EEPROM bytes.
Here's how linux decodes the EEPROM on Hauppauge cards:

http://www.sakoman.com/git/?p=linux.git;a=blob;f=drivers/media/video/tveeprom.c;h=6103d1b1081ee9e713746f3bd9e5dbde62e5e1ee;hb=HEAD#l419

Regards,
Andy


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Re: expansion board identification

Peter A. Bigot
On 08/27/2013 06:59 AM, Andy Walls wrote:

> All of my Tobi's came with the EEPROM unprogrammed/erased. Gumstix has
> a script to provision them:
> meta-gumstix-extras/recipes-core/i2c-tools/omap3-writeprom/writeprom.sh
>> It would be nice if this feature could be used to determine which
>> GPIOs should be configured for which function (LED, button, etc). If
>> the contents from the factory can't be relied upon, then I'd at least
>> like to be able to use it for other purposes.
> The defacto format of the EEPROM is documented here:
> http://elinux.org/BeagleBoardPinMux#Expansion_boards U-boot for the
> Overo looks for more than that - 94 bytes max - but leaves about 162
> bytes for whatever you want.

Thanks (and to Scott for the Tobi example).  Odd that the R2734 Summit I
have doesn't have an EEPROM (at least, the probe doesn't evoke a
response on any address on bus 2).

I have a u-boot patch for the Alto35 that's based on one I found in a
side branch of the gumstix u-boot fork, and have gotten it to work on
the dylan branch; all that's needed is for Gumstix to assign a device ID
so the patch can be finalized.

Peter

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Re: expansion board identification

Ash Charles
On Tue, Aug 27, 2013 at 5:21 AM, Peter A. Bigot <[hidden email]> wrote:
> I have a u-boot patch for the Alto35 that's based on one I found in a
> side branch of the gumstix u-boot fork, and have gotten it to work on
> the dylan branch; all that's needed is for Gumstix to assign a device ID
> so the patch can be finalized.

Thanks for the patch.  I've pushed this to the gumstix u-boot repo as
well as updating the meta-gumstix layer. I've also allocated some
additional EEPROM ids for Stagecoach, Thumbo and Turtlecore.

--Ash

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