EEPROM

EEPROM stands for Electrically Erasable Programmable Read-Only Memory. It is a non-volatile memory that can be programmed and erased electrically. The nonvolatile memory available on the phyCORE-AM62x is a 4kB EEPROM with an I2C interface. It can be accessed through the I2C0 on the phyCORE-AM62x at address 0x50. EEPROM can be used to store configuration data or other general-purpose data. This guide will show you how to access the 2kbit EEPROM featured on the phyCORE-AM62x development kit carrier board. To learn more information about the phyCORE-AM62x EEPROM system memory, please see section 6.1.2 in the Hardware Manual.

Note

The phyCORE-AM62x development kit provides access to two EEPROMs, 1x 32kbit EEPROM on the SOM and a 2kbit EEPROM on the carrier board.

EEPROM

Location	Reference	I2C Bus	Address
SOM	U20	i2c0	0x50
Carrier Board	U38	i2c1	0x51

Carrier Board EEPROM

EEPROM Initialization

• First ensure that the EEPROM is initialized correctly by checking the boot log.

  phyboard-lyra-am62xx-3:~# dmesg | grep -i "eeprom"
  [    6.049192] at24 0-0050: 4096 byte 24c32 EEPROM, writable, 32 bytes/write
  [    6.090717] at24 1-0051: 256 byte 24c02 EEPROM, writable, 16 bytes/write
  

Writing to the EEPROM

• Clear out the entirety of the EEPROM by writing zeros to it.

  phyboard-lyra-am62xx-3:~# dd if=/dev/zero of=/sys/bus/i2c/devices/1-0051/eeprom bs=256 count=1
  1+0 records in
  1+0 records out
  256 bytes copied, 0.0780454 s, 3.3 kB/s
  

• Now generate a 2kbit file with random data. This will serve as the test file:

  phyboard-lyra-am62xx-3:~# dd if=/dev/urandom of=/tmp/test.img bs=256 count=1
  1+0 records in
  1+0 records out
  256 bytes copied, 0.000466573 s, 549 kB/s
  

• Write the test file to the EEPROM

  phyboard-lyra-am62xx-3:~# dd if=/tmp/test.img of=/sys/bus/i2c/devices/1-0051/eeprom bs=256 count=1
  0+1 records in
  0+1 records out
  256 bytes copied, 0.0875027 s, 2.9 kB/s
  

Reading from EEPROM

• Read the contents of the EEPROM and store it to a file.

  phyboard-lyra-am62xx-3:~# dd if=/sys/bus/i2c/devices/1-0051/eeprom of=/tmp/test_read.img bs=256 count=1
  1+0 records in
  1+0 records out
  256 bytes copied, 0.0136441 s, 18.8 kB/s
  

• Make sure the output file was not corrupted during the transfer using md5sum.

  phyboard-lyra-am62xx-3:~# md5sum /tmp/test.img /tmp/test_read.img
  192e08b78bc0100bcff74d324d1ccbde  /tmp/test.img
  192e08b78bc0100bcff74d324d1ccbde  /tmp/test_read.img
  

SOM EEPROM (Limited Access)

PHYTEC Board Support Packages (BSPs) are equipped with extended functionality in the bootloader that allows it to read the System on Module (SOM) EEPROM. This enables the software to adjust based on the SOM configuration, allowing a single software image to work across multiple hardware configurations.

While modifying the SOM EEPROM content is not recommended, it is possible to disable this feature if needed. However, disabling it may require additional effort to support various SOM options.

You can access the SOM EEPROM content using the EEPROM Flashtool. Below is an overview of how to read the content and add new information. For further details, please refer to the official GitHub page.

Read the Content

To read the full content of the SOM EEPROM, use the pre-installed phytec_eeprom_flashtool. This tool will display all the relevant information stored in the SOM.

phyboard-lyra-am62xx-3:~# phytec_eeprom_flashtool read -som PCM-071

MAC Address

By default, the phyCORE-AM62x does not have pre-programmed MAC addresses and instead generates random MAC addresses at boot time. You can write specific MAC addresses into the SOM EEPROM using the EEPROM Flashtool, which will be read during the boot process.

Example command to set a MAC address 00:91:da:dc:1f:c5 for Ethernet interface 0:

phyboard-lyra-am62xx-3:~# phytec_eeprom_flashtool add-mac -som PCM-071 0 00:91:da:dc:1f:c5

Key Values

The SOM EEPROM can also store key-value pairs in ASCII format. These pairs will be read by the bootloader and stored in the environment, where they can be used either in the bootloader or accessed in Linux via the fw_printenv tool.

Example command to set the value CAFE1234 for the key SERIAL.

phyboard-lyra-am62xx-3:~# phytec_eeprom_flashtool add-key-value -som PCM-071 SERIAL CAFE1234