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Using I2C in Linux

Owned by Albinleo Velappan (Deactivated)

Last updated: 06. Oct 2022

3 min read

1 Using I2C in Linux
- 1.1 Myon I
- 1.2 Trizeps VII
- 1.3 Trizeps VIII
- 1.4 Trizeps VIII Mini
- 1.5 Trizeps VIII Plus
- 1.6 Myon II
- 1.7 SBCSOM
2 Use I2C from the Command Line
- 2.1 Scan for available I2C devices
- 2.2 Read from I2C device
- 2.3 Write to I2C device
- 2.4 Other I2C Commands

Using I2C in Linux

The Trizeps and Myon CPU modules may be configured to have multiple I2C busses.

Myon I

Pins	IO-Port	Driver Index	Description

Pins	IO-Port	Driver Index	Description
66,68	I2C4	3	typical connected to touch-controller
119,121	I2C6	5	I2C devices

Trizeps VII

Pins	Port	Driver Index	Description

Pins	Port	Driver Index	Description
194,196	I2C2	1	primary I2C interface
94,96	I2C1	0	secondary I2C interface

The PMFP0100 PMIC (7-bit address 0x08) of the Trizeps VII is connected to the primary I2C interface.

Trizeps VIII

Pins	Port	Driver Index	Description

Pins	Port	Driver Index	Description
194,196	I2C2	1	primary I2C interface
94,96	I2C1	0	secondary I2C interface
-	I2C3	2	internal I2C interface

The following devices are attached to the internal I2C interface:

7bit	8bit	Description

7bit	8bit	Description
0x08	0x10	PMFP0100 PMIC
0x10	0x20	MKV11 Kinetis MCU
0x1A	0x34	WM8983 Audio Codec
0x2C	0x58	MIPI to LVDS transceiver
0x40	0x80	FPGA primary config address
0x41	0x82	FPGA primary user mode
0x42	0x84	FPGA secondary user mode
0x43	0x86	FPGA primary config reset
0x60	0xC0	VDD_SOC regulatur

Trizeps VIII Mini

Pins	Port	Driver Index	Description

Pins	Port	Driver Index	Description
194,196	I2C2	1	primary I2C interface
94,96	I2C1	0	secondary I2C interface
-	I2C3	2	internal I2C interface

The following devices are attached to the internal I2C interface:

7bit	8bit	Description

7bit	8bit	Description
0x10	0x20	MKV11 Kinetis MCU
0x1A	0x34	WM8983 Audio Codec
0x2C	0x58	MIPI to LVDS transceiver
0x40	0x80	FPGA primary config address
0x41	0x82	FPGA primary user mode
0x42	0x84	FPGA secondary user mode
0x43	0x86	FPGA primary config reset
0x4B	0x96	BD71847 PMIC

Trizeps VIII Plus

Pins	Port	Driver Index	Description

Pins	Port	Driver Index	Description
194,196	I2C2	1	primary I2C interface
94,96	I2C1	0	secondary I2C interface
-	I2C3	2	internal I2C interface

The following devices are attached to the internal I2C interface:

7bit	8bit	Description

7bit	8bit	Description
0x10	0x20	MKV11 Kinetis MCU
0x1A	0x34	WM8983/WM8962B Audio Codec
0x25	0x4A	PCA9450 PMIC
0x40	0x80	FPGA primary config address
0x41	0x82	FPGA primary user mode
0x43	0x86	FPGA primary config reset
0x4A	0x94	WM8962B test functionality
0x69	0xD2	WM8962B test functionality
0x78	0xF0	???

Myon II

Pins	Port	Driver Index	Description

Pins	Port	Driver Index	Description
J70-66,68	I2C2	1	primary I2C interface
J71-67,69	I2C1	0	secondary I2C interface
J71-19,21	I2C3	2	internal I2C interface
[J70-73,75]	I2C4	3	special mounting option!

The following devices are attached to the internal I2C interface:

7bit	8bit	Description

7bit	8bit	Description
0x1A	0x34	WM8983 Audio Codec
0x2C	0x58	MIPI to LVDS transceiver
0x4B	0x96	BD71847 PMIC

SBCSOM

Pins	Port	Driver Index	Description

Pins	Port	Driver Index	Description
L.A04,A05	I2C1	0	left connector, i-MOD I2C, Mini-PCIe socket
R.A04,A05	I2C2	1	right connector, camera , KuK-MODIS
–	I2C3	2	internal I2C interface

The following devices are attached to the internal I2C interface:

7bit	8bit	Description

7bit	8bit	Description
0x1A	0x34	WM8983 Audio Codec
0x2C	0x58	MIPI to LVDS transceiver
0x39	0x72	HDMI transceiver
0x49	0x92	Secure Element
0x4B	0x96	BD71847 PMIC
0x50	0xA0	EEPROM

Use I2C from the Command Line

Please view the man-pages of the commands for details. The below instructions are only for a quick reference. On Debian, these tools are contained in the package i2c-tools. Install it with:

sudo apt install i2c-tools

Scan for available I2C devices

In this example we scan the internal I2C interface of Trizeps VIII.

$ i2cdetect -y 2

Which will output:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- 08 -- -- -- -- -- -- --
10: 10 -- -- -- -- -- -- -- -- -- 1a -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: 40 UU -- 43 -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: 60 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

The '-y' option is used to prevent the 'Continue? [Y/n]' question.
'2' is the Driver-Index of the I2C3 interface.
The output shows the found I2C-devices. 'UU' indicates that a driver for this device has been loaded. In the above case it is a driver that communicates with the Trizeps VIII FPGA.

Read from I2C device

In this example outputs the ID-register of the Trizeps VIII FPGA (depends on FPGA programming):

The '-f' option forces access to device 0x41. This is used, because a driver for this address has already been loaded and will prevent access without the force option.
The '-y' option is used to prevent the 'Continue? [Y/n]' question.
'2' is the Driver-Index of the I2C3 interface.
'0x41' is the 7bit I2C-address of the Trizeps VIII FPGA. '0' is the ID-register offset.

Write to I2C device

This will write to register 0x10 of device connected to 0x41. In this specific case it disables conversion of the MIPI-DSI stream.
The '-f' option forces access to device 0x41. This is used, because a driver for this address has already been loaded and will prevent access without the force option.
The '-y' option is used to prevent the 'Continue? [Y/n]' question.
'2' is the Driver-Index of the I2C3 interface.
'0x41' is the 7bit I2C-address of the Trizeps VIII FPGA. '0x10' is the display control register.

Other I2C Commands

'i2ctransfer' may be used to have better control on how an I2C packet is sent (Multiple bytes write & read).
'i2cdump' may be used to dump registers of an I2C device.