Example EEPROM¶

As noted in the Development Kit data-sheet:

A 256 Kbit EEPROM, U11, is available for user configuration information on the
MitySOM-AM57(F) Development Board. This EEPROM is accessible over the I2C5
interface to the AM57xx processor.

Goal¶

These notes indicate how to access the Baseboard EEPROM from within Linux.

Prerequisites¶

• I2C5 as indicated in the data sheet is known internally to Linux as i2c-4.
• The address of the EEPROM device is 50.
• The device file for the EEPROM is /sys/bus/i2c/devices/4-0050/eeprom

Steps¶

• Display the current values in the eeprom.
  

  root@mitysom-am57x:~# od -xc /sys/bus/i2c/devices/4-0050/eeprom
  0000000     ffff    ffff    ffff    ffff    ffff    ffff    ffff    ffff
           377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
  *
  0100000
  root@mitysom-am57x:~#
  
  # The above indicates that all of the bytes in the eeprom have values of 0xff.
  

• Write values to the eeprom.
  

  root@mitysom-am57x:~# echo Hello World > /sys/bus/i2c/devices/4-0050/eeprom
  

• Display the just written value in the eeprom
  

  root@mitysom-am57x:~# od -xc /sys/bus/i2c/devices/4-0050/eeprom
  0000000     6548    6c6c    206f    6f57    6c72    0a64    ffff    ffff
             H   e   l   l   o       W   o   r   l   d  \n 377 377 377 377
  0000020     ffff    ffff    ffff    ffff    ffff    ffff    ffff    ffff
           377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
  *
  0100000
  root@mitysom-am57x:~# 
  

• Bulk read of entire contents.
  

  root@mitysom-am57x:~# dd if=/sys/bus/i2c/devices/4-0050/eeprom of=eeprom_contents bs=4096 count=8
  8+0 records in
  8+0 records out
  
  # verify contents
  root@mitysom-am57x:~# od -cx eeprom_contents
  0000000    H   e   l   l   o       W   o   r   l   d  \n 377 377 377 377
              6548    6c6c    206f    6f57    6c72    0a64    ffff    ffff
  0000020  377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
              ffff    ffff    ffff    ffff    ffff    ffff    ffff    ffff
  *
  0100000
  root@mitysom-am57x:~#
  
  

• Writing 0's to entire contents
  

  root@mitysom-am57x:~# dd if=/dev/zero of=/sys/bus/i2c/devices/4-0050/eeprom bs=4096 count=8
  8+0 records in
  8+0 records out
  root@mitysom-am57x:~# od -cx /sys/bus/i2c/devices/4-0050/eeprom
  0000000   \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
              0000    0000    0000    0000    0000    0000    0000    0000
  *
  0100000
  root@mitysom-am57x:~#
  

• Writing 0xff to entire contents
  

  # use tr to translate the 0's to 0xff
  root@mitysom-am57x:~# cat /dev/zero | tr "\0" "\xff" | dd  of=/sys/bus/i2c/devices/4-0050/eeprom bs=4096 count=8
  8+0 records in
  8+0 records out
  root@mitysom-am57x:~# od -cx /sys/bus/i2c/devices/4-0050/eeprom
  0000000  377 377 377 377 377 377 377 377 377 377 377 377 377 377 377 377
              ffff    ffff    ffff    ffff    ffff    ffff    ffff    ffff
  *
  0100000
  root@mitysom-am57x:~#
  
  

Conclusion¶

Given one or more of the commands above, you should be able to read and write the EEPROM. Similar operations could be performed in a program.