i2cdump

Dump all registers of an I2C device

$ i2cdump [i2cbus] [device_address]

$ i2cdump -y [i2cbus] [device_address]

$ i2cdump [i2cbus] [device_address] [b|w|c|s|i]

$ i2cdump -r [start]-[end] [i2cbus] [device_address]

i2cdump [-y] [-f] [-r first-last] [-V] [-l] [-u] i2c-bus address [mode]

i2c-bus
    The I2C bus number or name to scan (e.g., 0, 1, /dev/i2c-0).

address
    The 7-bit hexadecimal address of the I2C device on the bus.

mode
    The dump mode. Options include:
b: Read individual bytes (default).
w: Read 16-bit words.
s: Read SMBus blocks.
i: Read generic I2C blocks.
c: Read entire chip memory (potentially dangerous).

-y
    Disable interactive mode. Assume 'yes' for all prompts, which can be dangerous for certain operations.

-f
    Force access to the I2C bus. Useful when the kernel thinks another driver is using the bus, but use with caution.

-r first-last
    Specify a range of registers to dump (e.g., 0x00-0x1F).

-V
    Display the version information and exit.

-l
    List all supported dump modes and exit.

-u
    Do not print empty lines in the output, making the display more compact.

i2cdump is a powerful command-line utility from the i2c-tools package used for examining the contents of registers on an I2C/SMBus device. It allows users to read and display data directly from an I2C chip's memory or registers at a specified address on a given I2C bus.

This tool is invaluable for embedded systems developers and hardware engineers for debugging I2C device drivers, verifying hardware functionality, or reverse-engineering unknown I2C devices. It supports various dump modes, including byte-level, word-level, SMBus block reads, and more generic I2C reads, providing flexibility based on the device's communication protocol.

While highly useful, i2cdump interacts directly with hardware, making it a potentially dangerous tool if misused. Proper care and understanding of the target device's datasheet are essential to avoid unintended side effects or hardware damage.

Hardware Interaction: i2cdump directly interacts with I2C hardware. Incorrect usage, especially with the -f (force) or -c (chip dump) options, can lead to unpredictable device behavior, data corruption, or even permanent hardware damage.

Permissions: Accessing I2C devices typically requires root privileges (e.g., using sudo) to access the /dev/i2c-* devices.

Bus Contention: If other kernel modules or applications are actively using the I2C bus, forcing access with -f can lead to bus contention, potentially disrupting ongoing communications or causing system instability.

To dump the first 32 bytes of device at address 0x50 on bus 1 (default byte mode):

sudo i2cdump 1 0x50

To dump specific registers (0x10 to 0x1F) in word mode on bus 0, address 0x22:

sudo i2cdump -r 0x10-0x1F 0 0x22 w

To list all supported dump modes:

i2cdump -l

i2cdump is a core utility within the i2c-tools suite, a collection of userspace programs for communicating with I2C/SMBus devices. Developed initially by Frodo Looijaard and later maintained by Jean Delvare, i2c-tools has been a staple in Linux kernel development and embedded systems debugging for many years. i2cdump's role has consistently been to provide a low-level view into I2C device registers, evolving with the I2C kernel subsystem to support various bus types and communication modes.

i2cdetect(8), i2cset(8), i2cget(8), i2c-tools(7)