Voltage Domain Configuration

Hardware Configuration

Each project must fill out this table to ensure that the actual hardware connections match the software configuration. It is imperative to confirm the match before compiling the firmware:

IO domain Actual Voltage Used Configurable Voltage Voltage Source Remarks
PMUIO1 3.3V Fixed Group with PMU
PMUIO2 3.3V 1.8/3.3 LDO6
VCCIO1 3.3V 1.8/3.3 LDO4/VCCIO_ACODEC Group with 809Codec
VCCIO2 1.8V 1.8/3.3 BUCK5 Group with EMMC
VCCIO3 3.3V 1.8/3.3 LDO5/VCCIO_SD Group with SD card
VCCIO4 1.8V 1.8/3.3 BUCK5 Group with BT/WIFI
VCCIO5 3.3V 1.8/3.3 VCC3V3_SYS Group with PCIE
VCCIO6 1.8V 1.8/3.3 BUCK5 Group with GMAC
VCCIO7 3.3V 1.8/3.3 VCC3V3_SYS

The first compilation will prompt you to configure the voltage domain, and the options are as follows:

  • PMUIO2:3.3V

    ../../_images/iodomain_pmuio2.png

  • VCCIO1:3.3V

    ../../_images/iodomain_vccio1.png

  • VCCIO3:3.3V

    ../../_images/iodomain_vccio3.png

  • VCCIO4:1.8V

    ../../_images/iodomain_vccio4.png

  • VCCIO5:3.3V

    ../../_images/iodomain_vccio5.png

  • VCCIO6:1.8V

    ../../_images/iodomain_vccio6.png

  • VCCIO7:3.3V

    ../../_images/iodomain_vccio7.png

DTS Configuration

File path: kernel/arch/arm64/boot/dts/rockchip/rk3568-evb.dtsi

&pmu_io_domains {
        status = "okay";
        pmuio2-supply = <&vcc3v3_pmu>;
        vccio1-supply = <&vccio_acodec>;
        vccio3-supply = <&vccio_sd>;
        vccio4-supply = <&vcc_1v8>;
        vccio5-supply = <&vcc_3v3>;
        vccio6-supply = <&vcc_1v8>;
        vccio7-supply = <&vcc_3v3>;
};

VCCIO Description

VCCIO Power Supply

  • If VCCIO2is powered by 1.8V,then the FLASH_VOL_SELpin must be kept high. The chip will automatically configure VCCIO2 to 1.8V mode based on FLASH_VOL_SEL=Logic high;

  • If VCCIO2 is powered by 3.3V, then the FLASH_VOL_SEL pin must be kept low. The chip will automatically configure VCCIO2 to 3.3V mode based on FLASH_VOL_SEL=Logic low;

  • If the power voltage supplied to VCCIO2 and the FLASH_VOL_SEL do not satisfy the above relationship, functions will be abnormal (such as unable to boot normally) or the IO may be damaged.

Software Voltage Configuration

  • When the hardware IO level is connected to 1.8V, the software voltage configuration must also be set to 1.8V. If it is mistakenly configured to 3.3V, the IO functions of this power domain will be abnormal;

  • When the hardware IO level is connected to 3.3V, the software voltage configuration must also be set to 3.3V. If it is mistakenly configured to 1.8V, it will cause the IO of this power domain to be over-voltage, and the IO will be damaged if it works for a long time.

Configuration in Code

  • In the RK3568_AIoT_REF_SCH reference diagram, the VCCIO3 power domain IO is by default allocated for SD Card function, The working modes of the SD Card are: SD2.0 mode and SD3.0 mode; the IO level of SD2.0 mode is 3.3V, and the IO level of SD3.0 mode is 1.8V;

  • In actual operation, it defaults to working in SD2.0 mode, that is, 3.3V IO. If the inserted card supports SD3.0, after negotiation, the IO level will switch to 1.8V IO, and then switch to the rate of running SD3.0;

  • In the reference diagram, the VCCIO3 IO power is supplied by RK809-5 LDO5 (network name is VCCIO_SD), which defaults to 3.3V. According to the working mode of the SD Card, RK3568 will configure the output voltage of RK809-5 LDO5 through I2C0.

  • For example, the default configuration of the IO domain in rk3568-evb.dtsi is vccio3-supply = <&vccio_sd>;

  • The related configuration of sdmmc0 is as follows:

&sdmmc0 {
    max-frequency = <150000000>;
    supports-sd;
    bus-width = <4>;
    cap-mmc-highspeed;
    cap-sd-highspeed;
    disable-wp;
    sd-uhs-sdr104;
    vmmc-supply = <&vcc3v3_sd>;
    vqmmc-supply = <&vccio_sd>;
    pinctrl-names = "default";
    pinctrl-0 = <&sdmmc0_bus4 &sdmmc0_clk &sdmmc0_cmd &sdmmc0_det>;
    status = "okay";
};

  • To support the full SD Card function, this configuration is sufficient. The software will automatically switch the IO voltage and the corresponding IO domain voltage mode according to the SD Card mode.

  • If there is no need to work in SD3.0 mode， and it only needs to be fixed in SD2.0 mode（even SD3.0 cards will only work in SD2.0 mode），such as when using a discrete power supply, and you want to save the circuit that switches from 3.3V to 1.8V, the hardware VCCIO3 IO power supply will be modified to VCC_3V3，and the software needs to make the following changes: The IO domain configuration is changed to vccio3-supply = <&vcc_3v3>;

  • The related configuration of sdmmc0 is modified as follows:

&sdmmc0 {
    max-frequency = <150000000>;
    supports-sd;
    bus-width = <4>;
    cap-mmc-highspeed;
    cap-sd-highspeed;
    disable-wp;
    vmmc-supply = <&vcc3v3_sd>;
    vqmmc-supply = <&vcc_3v3>;
    pinctrl-names = "default";
    pinctrl-0 = <&sdmmc0_bus4 &sdmmc0_clk &sdmmc0_cmd &sdmmc0_det>;
    status = "okay";
};

  • It is necessary to remove sd-uhs-sdr104. If not removed, it will run in SD3.0 mode, and high-speed cards will fail to read.

  • If the VCCIO3 power domain IO is allocated to other functions, such as UART5、UART6functions, then follow the note Software Voltage Configuration