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The Linux kernel provides a device driver for the I2C controller of the i.MX RT BSPs, enabled in the kernel with the CONFIG_I2C_IMX_LPI2C build-time option. Another kernel configuration option that you will require is CONFIG_I2C_CHARDEV. This option enables the kernel API that allows accessing I2C devices from user-space application code. These kernel configuration options are enabled by default in the rootfs project.

The i.MX RT1024 and i.MX RT1050 RT10XX devices provide four I2C bus controllers, while the i.MX RT1170 device provides six I2C bus controllers. The parameters of each bus controller are specified in the lpi2c* child nodes properties in the corresponding linux/arch/arm/boot/dts/<bsp>.dtsi file:

  • For the i.MX RT1024 in linux/arch/arm/boot/dts/imxrt1020.dtsi:

    Code Block
    lpi2c1: lpci2c@403f0000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403f0000 0x4000>;
    interrupts = <28>;
    clocks = <&clks IMXRT1020_CLK_LPI2C1>, <&clks IMXRT1020_CLK_PER_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c2: lpci2c@403f4000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403f4000 0x4000>;
    interrupts = <29>;
    clocks = <&clks IMXRT1020_CLK_LPI2C2>, <&clks IMXRT1020_CLK_PER_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c3: lpci2c@403f8000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403f8000 0x4000>;
    interrupts = <30>;
    clocks = <&clks IMXRT1020_CLK_LPI2C3>, <&clks IMXRT1020_CLK_PER_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c4: lpci2c@403fc000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403fc000 0x4000>;
    interrupts = <31>;
    clocks = <&clks IMXRT1020_CLK_LPI2C4>, <&clks IMXRT1020_CLK_PER_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

  • For the i.MX RT1050/RT1060 in linux/arch/arm/boot/dts/nxp/imx/imxrt1050.dtsi:

    Code Block
    lpi2c1: lpci2c@403f0000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403f0000 0x4000>;
    interrupts = <28>;
    clocks = <&clks IMXRT1050_CLK_LPI2C1>, <&clks IMXRT1050_CLK_IPG_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c2: lpci2c@403f4000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403f4000 0x4000>;
    interrupts = <29>;
    clocks = <&clks IMXRT1050_CLK_LPI2C2>,  <&clks IMXRT1050_CLK_IPG_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c3: lpci2c@403f8000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403f8000 0x4000>;
    interrupts = <30>;
    clocks = <&clks IMXRT1050_CLK_LPI2C3>,  <&clks IMXRT1050_CLK_IPG_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c4: lpci2c@403fc000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x403fc000 0x4000>;
    interrupts = <31>;
    clocks = <&clks IMXRT1050_CLK_LPI2C4>,  <&clks IMXRT1050_CLK_IPG_PODF>;
    clock-names = "per", "ipg";
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

  • For the i.MX RT1170 in linux/arch/arm/boot/dts/imxrt1170.dtsi:

    Code Block
    lpi2c1: lpci2c@40104000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x40104000 0x4000>;
    interrupts = <32>;
    clocks = <&clks IMXRT1170_CLK_LPI2C1>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c2: lpci2c@40108000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x40108000 0x4000>;
    interrupts = <33>;
    clocks = <&clks IMXRT1170_CLK_LPI2C2>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c3: lpci2c@4010c000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x4010c000 0x4000>;
    interrupts = <34>;
    clocks = <&clks IMXRT1170_CLK_LPI2C3>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

lpi2c4: lpci2c@40110000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x40110000 0x4000>;
    interrupts = <35>;
    clocks = <&clks IMXRT1170_CLK_LPI2C4>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};
lpi2c5: lpci2c@40c34000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x40c34000 0x4000>;
    interrupts = <36>;
    clocks = <&clks IMXRT1170_CLK_LPI2C5>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};
lpi2c6: lpci2c@40c38000 {
    compatible = "fsl,imx7ulp-lpi2c";
    reg = <0x40c38000 0x4000>;
    interrupts = <37>;
    clocks = <&clks IMXRT1170_CLK_LPI2C6>;
    #address-cells = <1>;
    #size-cells = <0>;
    status = "disabled";
};

Assignment of the I2C signals to specific pins is described in the pinctrl_lpi2c* child nodes of the iomuxc node in projects/rootfs/rootfs.dts.< bsp><bsp>:

  • For the i.MX RT1024:

    Code Block
    ...
    pinctrl_lpi2c1: i2c1grp {
        fsl,pins = < 
            MXRT1020_IOMUXC_GPIO_AD_B1_14_LPI2C1_SCL  MXRT10XX_PAD_CFG_I2C
            MXRT1020_IOMUXC_GPIO_AD_B1_15_LPI2C1_SDA  MXRT10XX_PAD_CFG_I2C
        >;
};
...

  • For the i.MX XRT1050/RT1060:

    Code Block
    ...
pinctrl_lpi2c1: lpi2cgrp {
        fsl,pins = < 
            MXRT1050_IOMUXC_GPIO_AD_B1_00_LPI2C1_SCL  MXRT10XX_PAD_CFG_I2C
            MXRT1050_IOMUXC_GPIO_AD_B1_01_LPI2C1_SDA  MXRT10XX_PAD_CFG_I2C
        >;
};
...

  • for the i.MX RT1170:

    Code Block
    ...
pinctrl_lpi2c5: lpi2cgrp5 {
        fsl,pins = < 
            IOMUXC_GPIO_LPSR_05_LPI2C5_SCL  (IMX_PAD_SION | \
                MXRT1170_PAD_DSE | \
                MXRT1170_PAD_PUE | \
                MXRT1170_PAD_PUS | \
                MXRT1170_PAD_SRE)
            IOMUXC_GPIO_LPSR_04_LPI2C5_SDA  (IMX_PAD_SION | \
                MXRT1170_PAD_DSE | \
                MXRT1170_PAD_PUE | \
                MXRT1170_PAD_PUS | \
                MXRT1170_PAD_SRE)
        >;
};
...

...

  • For the i.MX RT1024:

    Code Block
    &lpi2c1 {
        pinctrl-names = "default";
        pinctrl-0 =  <&pinctrl_lpi2c1>;
        status = "okay";
...
};

  • For the i.MX RT1050/RT1060:

    Code Block
    &lpi2c1 {
        pinctrl-names = "default";
        pinctrl-0 =  <&pinctrl_lpi2c1>;
        status = "okay";
...
};

  • For the i.MX RT1170:

    Code Block
    &lpi2c5 {
        pinctrl-names = "default";
        pinctrl-0 =  <&pinctrl_lpi2c5>;
        status = "okay";
...
};

...

  • Scan I2C1 bus on the i.MX RT1024 EVK board:

    Code Block
    / # i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
/ #

  • Scan I2C1 bus on the i.MX RT1050 EVK /RT1060 EVKB board:

    Code Block
    / # i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- 1f
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- 38 -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 -- -- -- -- -- -- -- 58 -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- -- 
/ #

  • Scan I2C5 bus on the i.MX RT1170 EVK board:

    Code Block
    / # i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- 1f
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
/ #

  • Scan I2C5 bus on the i.MX RT1170 EVKB board:

    Code Block
    / # i2cdetect -y 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- 4a -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
/ #

...

  • For the i.MX RT1024 EVK board:

    • SDA of EEPROM is connected to J18.10;

    • SCL of EEPROM is connected to J18.12;

    • VCC of EEPROM is connected to J19.16;

    • GND of EEPROM is connected to J18.1.

  • For the i.MX RT1050/RT1060 EVK board:

    • SDA of EEPROM is connected to J23.5;

    • SCL of EEPROM is connected to J23.6;

    • VCC of EEPROM is connected to J21.2;

    • GND of EEPROM is connected to J21.8.

  • For the i.MX RT1170 EVK or EVKB board:

    • SDA of EEPROM is connected to J10.18;

    • SCL of EEPROM is connected to J10.20;

    • VCC of EEPROM is connected to J10.16;

    • GND of EEPROM is connected to J10.14.

...