Table of Contents

Overview

This script writes TLV (Type-Length-Value) structured data into an I2C EEPROM. It supports a variety of system-specific keys that define metadata for the device.

The script:

Dependencies

To ensure all required dependencies are installed, run:

sudo apt update
sudo apt install python3 python3-smbus

this will:

Usage

python3 TLV_write.py <i2c_bus> <eeprom_address> [--yes] [-b] <key> <value> <key> <value> ...

Arguments

Argument

Description

i2c_bus

The I2C bus number.

eeprom_address

The EEPROM address (hex or decimal).

--yes
-y
--force

Automatically confirms the operation (skips user confirmation).

-b

Writes the TLV data to a binary file (/tmp/eeprom_tlv.bin) without writing to the EEPROM. You can later write it manually using dd.

<key> <value>

One or more key-value pairs to write to EEPROM.

Example Usage

For example if we want the following data to appear in DMI:

Handle 0xXXXX, DMI type 1, XX bytes
System Information
	Manufacturer: XXXXX
	Product Name: MySystem
	Version: 1.0
	Serial Number: XXXXXX
	UUID: XXXXXX-XXXXX-XXXXX-XXXXX-XXXXX
	Wake-up Type: XXXXXXXXXXXX
	SKU Number: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
	Family: XXXXXXXXXXXXXXXXXXXXXXX

We want to run the following command (Note that bus 3 address 0X50 is used in this example):

python3 TLVwriter.py 3 0x50 TLV_CODE_SYS_NAME "MySystem" TLV_CODE_SYS_VERSION "1.0"

eeprom example for this :

python3 TLVwriter.py 3 0x50 TLV_CODE_SYS_NAME "EmbeddedDevice" \
      TLV_CODE_SYS_SKU "ED-2024" \
      TLV_CODE_SYS_SERIAL_NUMBER "SN123456789" \
      TLV_CODE_SYS_VERSION "01.02" \
      TLV_CODE_FAMILY "Industrial" \
      TLV_CODE_MANUF_NAME "Solid-Run" \
      TLV_CODE_MANUF_DATE "2024-03-11" \
      TLV_CODE_PLATFORM_NAME "Bedrock-IPC"

00: 54 6c 76 49 6e 66 6f 00 01 65 00 30 0e 45 6d 62 TlvInfo.?e.0?Emb
10: 65 64 64 65 64 44 65 76 69 63 65 31 07 45 44 2d eddedDevice1?ED-
20: 32 30 32 34 32 0b 53 4e 31 32 33 34 35 36 37 38 20242?SN12345678
30: 39 33 05 30 31 2E 30 32 20 0a 49 6e 64 75 73 74 93?01.02 ?Indust
40: 72 69 61 6c 25 09 73 6f 6c 69 64 2d 72 75 6e 23 rial%.solid-run#
50: 0a 32 30 32 34 2d 30 33 2d 31 31 24 0b 42 65 64 .2024-03-11$.Bed
60: 72 6f 63 6b 2d 49 50 43 fe 04 6e 7e c0 fd 00 00 rock-IPC??n~??
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: ……

header

version

Total Payload Length (little endian)

Type

Length

Value

crc checksum TLV

Finding the I2C Bus Number

To determine the correct I2C bus number, run the following command:

sudo i2cdetect -y 1

If no EEPROM device is found, repeat the command with different bus numbers (e.g., 2, 3, 4, etc.) until you detect an address 0x50 or 0x56. Once found, use the corresponding bus number in the script.

Example:

sudo i2cdetect -y 2

If the output shows:

     0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

Then bus 2 and address 0x50 should be used in the script.

Supported TLV Keys

Each TLV Key has a Hex Code, Max Length, and belongs to a DMIDecode Type.

System Information (SMBUS Type 1)

TLV Key

Max Length (bytes)

BIOS path

TLV_CODE_FAMILY

20

-

TLV_CODE_MANUF_DATE

10

-

TLV_CODE_PLATFORM_NAME

20

-

TLV_CODE_MANUF_NAME

20

-

TLV_CODE_VENDOR_NAME

20

-

TLV_CODE_SYS_NAME

20

Main → Detailed Configuration Information → Model

TLV_CODE_SYS_SKU

20

Main screen

TLV_CODE_SYS_SERIAL_NUMBER

24

Main screen

TLV_CODE_SYS_VERSION

5

-

NIO Information (SMBUS Type 2)

TLV Key

Max Length (bytes)

TLV_CODE_NIO_NAME

20

TLV_CODE_NIO_SERIAL_NUMBER

24

TLV_CODE_NIO_VERSION

5

Chassis Information (SMBUS Type 3)

TLV Key

Max Length (bytes)

TLV_CODE_CHS_SERIAL_NUMBER

24

TLV_CODE_CHS_VERSION

5

TLV Key

Max Length (bytes)

BIOS path

TLV_CODE_CONFIG_CODE

200

Main → Detailed Configuration Information → Configuration String

Error Handling

If invalid input is provided, the script will:

Possible Errors

Error Message

Cause

Error: Unknown key

Provided TLV key is not in the supported list.

Error: Value for key 'X' is too long

Input exceeds the maximum allowed length.

Error: MAC address must have 6 parts

Incorrect MAC format.

Error: I2C write error

I2C communication issue during EEPROM write.

Error: Total TLV data length exceeds EEPROM capacity

Data is too large for EEPROM storage.