I2C¶
Available I2C buses¶
List of available I2C buses on VAR-SOM-MX8
# ls -l /dev/i2c-*
crw-rw---- 1 root i2c 89, 0 Jun 26 2025 /dev/i2c-0
crw-rw---- 1 root i2c 89, 1 Jun 26 2025 /dev/i2c-1
crw-rw---- 1 root i2c 89, 4 Jun 26 2025 /dev/i2c-4
System class on VAR-SOM-MX8:
List of available I2C buses on SPEAR-MX8
# ls -l /dev/i2c-*
crw------- 1 root root 89, 1 Jul 16 12:22 /dev/i2c-1
crw------- 1 root root 89, 4 Jul 16 12:22 /dev/i2c-4
System class on SPEAR-MX8:
I2C devices per bus¶
Scan bus 0:
# i2cdetect -y -r 0
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- UU -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Scan bus 1:
# i2cdetect -y -r 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- UU -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Scan bus 4:
# i2cdetect -y -r 4
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- 54 55 -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
When the device is marked with "UU" it means that a driver is using it. When the device is marked with numbers it means that no driver is using it.
Reading / Writing from an I2C device¶
Variscite includes I2CTools as a part of the default file system build, examples of optional commands: i2cdump - dump the content of an I2C device i2cset - write a single character to an I2C device i2cget - read a single character to an I2C device
In addition follow 'C' code example as describe in the linux kernel documentation : https://www.kernel.org/doc/Documentation/i2c/dev-interface
Variscite's system integrated I2C devices¶
Note: Do not write to Variscite's on-SOM EEPROM or you will damage the SOM!
Variscite devices on VAR-SOM-MX8:
I2C-0 0x1a - Audio codec on SOM
I2C-0 0x52 - EEPROM on SOM. Don't modify!
I2C-0 0x53 - EEPROM on SOM. Don't modify!
I2C-1 0x20 – GPIO expander on carrier board
I2C-1 0x3c – MIPI-CSI camera on expansion board
I2C-1 0x3d – USB Type C controller on carrier board
I2C-4 0x38 – Capacitive touch controller on kit display
I2C-4 0x54 - EEPROM on carrier board
I2C-4 0x55 - EEPROM on carrier board
I2C-4 0x68 – RTC on carrier board
Variscite devices on SPEAR-MX8:
I2C-0 0x38 – Capacitive touch controller on kit display
I2C-0 0x54 - EEPROM on carrier board
I2C-0 0x55 - EEPROM on carrier board
I2C-0 0x68 – RTC on carrier board
I2C-1 0x3d – USB Type C controller on carrier board
I2C-2 0x08 – USB3 Hub
I2C-4 0x1a - Audio codec on SOM
I2C-5 0x3c – MIPI-CSI camera on expansion board
I2C-6 0x3c – MIPI-CSI camera on expansion board