[Fx30] Reading EEPROM of the expansion card


I am making use of several expansion cards on my system. I would like my application (plain C, outside Legato) to know what is the expansion card inserted.

Looking at “/sys/class/i2c-adapter/i2c-0/” I see several elements which seems to be I2C devices… but which one is the EEPROM if the expansion card? This list does not change if I insert or not an expansion card.

Using IOT_Detect (GPIO25) I can see if there is a card connected or not.

How can I read the content (from Linux terminal) of the EEPROM to get information on the expansion card connected?
I have installed “i2c-tools” but it doesn’t help.

A simple read example using C or Python or Shell would be greatly appreciated.

Thanks to help, regards, Christian.

Hi Christian,
You can determine which device the EEPROM is by checking the name of the specific device.

For example,
cat /sys/class/i2c-adapter/i2c-0/0-0020/name

will output:

which is the GPIO expander chip.

The I2C devices are present on the IOT card what’s additional to:


Hello Chris,

Thanks for the answer but I do not observe new elements appearing in the /sys/class/i2c-adapter/i2c-0 folder when I connect an expansion card… even after a power cycle.

I have tested with all expansion cards I have: Renfell GPIO / Renfell RS485 / Talon Ethernet / Energiya Converter.

I am able to see the I2C address of the EEPROM in 0x53 (for all except the Renfell GPIO Card) using “i2cdetect -y -r 0”.

As suggested in the “ Recommended EEPROM Schematic” of the " IoT Expansion Card Design Specification (Rev8) " of “http://mangoh.io” site, I see that by changing the output value to 1 of the CARD_DETECT (setting the expansion card to ACTIVE) The EEPROM address moves to 0x52.

Using the I2C dump command “i2cdump -y 0 0x52 c 0”, I can see the content of the EEPROM of Energiya Converter Expansion card, but I cannot see the EEPROM content of the other expansion cards.

I am a bit confused with this EEPROM reading and expansion card name that should appear in /sys/class/i2c-adapter/i2c-0 but does not. Could you check what’s going on.

Thanks, Christian.

P.S.: I have tested with several expansion cards and several Fx30 (including one with the reference firmware SWI9X15Y_07.11.22.00 r33729 CARMD-EV-FRMWR1 2017/01/11 18:04:06)

Hi Christian,
Sorry, I tried with an IOT card I have here and you’re right, I don’t see the card’s EEPROM in /sys/devices/i2c-0 either.

I’m not familiar with the Renfell cards, are you certain the GPIO card has an EEPROM? Have you consulted with them?

I tried a Talon ethernet card but I was only able to read all 0xFF’s.


Hello Chris,

Yes, all cards I have up to now have an EEPROM… It’s a good thing to be able to differentiate the expansion card… if we can read them. Maybe is there something I am doing wrong… please keep me updated if you manage to have it working.

Regards, Christian.