I2C
Accessing the external I2C bus
The i.mx 8M Plus has a number of I2C busses on board. Internally they are connected to a variety of onboard peripherals. Normally you will not need to address these peripherals directly, and they will be handled by Linux drivers.
I2C1 - SOM only for PMIC control
I2C2 - MIPI CSI1, LVDS1, DSI
I2C3 - MIPI CS2, LVDS2, PCIe
I2C4 - USB1 TCPC, USB2 TCPC, Secure Element, RTC
TCPC1 I2C ADDR: 1010001X
TCPC2 I2C ADDR: 1010010X
RTC I2C ADDR: 1010011X
PD1 I2C ADDR: 1110010X
PD2 I2C ADDR: 1110011X
SE050 I2C ADDR: 1001000X
External I2C #6 on AUX Connector
AUX connector: I2C bus #6 is pin-muxed with UART4 to the six pin JST-GH J12 connector and is the external I2C bus is enabled on the AUX port of the NavQ+. By default these are configured for I2C and not UART4 (internal MCU)
Note that UART4 typically is used to connect to the internal Microcontroller of the i.MX 8M Plus, and it is also pinmuxed on J11. The two alternative pinmuxing locations are so a custom Linux DTB could be configured depending on your needs for UART4, SPI2 or I2C.
A table of the J12 pinout is below. Note that pin 1 is on the left side of the connector:
| Pin | Function | Voltage |
|---|---|---|
1 | 5V | 5V |
2 | I2C_SDA | 3V3 |
3 | I2C_SCL | 3V3 |
4 | GPT1_CAPTURE1 | 3V3 |
5 | GPT1_CAPTURE2 | 3V3 |
6 | GND | GND |
You only need to use pins 1, 2, 3, and 6 for I2C. These GPIO are 3.3 volt tolerant only.
I2C device detection
To detect that a device is present on the bus, you can run the following command:
You may need to add the 'user' user to the i2c group to access the bus. To do this, run the following command, then log out and log back in:
Secure Element and i2ddetect
The SE050 or SE05x secure element will not respond to an i2cdetect command. "Plug and Trust" software library should be used to interface with the external Secure Element.
I2C (I2C6) Locator
Schematic
The I2C port is multiplexed with UART4 on the NavQPlus. This is configured in the Linux DTB files. Therefore the schematic below shows the UART signal names. The Multiplexed I2C signal names are shown on the far left of the image
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