i.MX8QXP set Dual Voltage Pad Level

[nolan_zinn]

I've been working with GPIOs on an i.MX8QXP MEK with Baseboard.  The particular GPIOs I've been using are on the Audio In connector on the bottom of the Baseboard, which I am using because I have a PCIe x8 ribbon cable, and I don't currently have any of the other connectors on the baseboard.  The GPIOs on this Audio In connector currently have a high logic level of 1.8V.  From threads like i.MX8 ADC_IN0 pin can't set as GPIO function, I have seen references to dual voltage pads.  In particular, SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD is what I'm referring to, which seems to indicate that the pad can output either 1.8V or 3.3V.  In my devicetree I have the following code:

&esai0 {
 status = "disabled";
};

&iomuxc {
 pinctrl-0 = <&pinctrl_hog>, <&pinctrl_nstatus>, <&pinctrl_confdone>, <&pinctrl_initdone>, <&pinctrl_nconfig>, <&pinctrl_nce>, <&pinctrl_trgoe>;
 imx8qxp-mek {
  pinctrl_nstatus: nstatus {
   fsl,pins = <
    SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0
    SC_P_ESAI0_SCKT_LSIO_GPIO0_IO03   0xE4000020 /* gpio 483 nSTATUS  open-drain-input, pull-up, high-drive*/
   >;
   gpios = <&gpio0 3 GPIO_ACTIVE_HIGH>;
  };
  pinctrl_confdone: confdone {
   fsl,pins = <
    SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0
    SC_P_ESAI0_FST_LSIO_GPIO0_IO01   0xE4000020 /* gpio 481 CONF_DONE open-drain-input, pull-up, high-drive*/
   >;
   gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
  };
  pinctrl_initdone: initdone{
   fsl,pins = <
    SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0
    SC_P_ESAI0_TX5_RX0_LSIO_GPIO0_IO09  0xE4000020 /* gpio 489 INIT_DONE open-drain-input, pull-up, high-drive*/
   >;
   gpios = <&gpio0 9 GPIO_ACTIVE_HIGH>;
  };
  pinctrl_nconfig: nconfig{
   fsl,pins = <
    SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0
    SC_P_ESAI0_SCKR_LSIO_GPIO0_IO02   0xE6000020 /* gpio 482 nCONFIG  in-out, pull-up, high-drive*/
   >;
   gpios = <&gpio0 2 GPIO_ACTIVE_HIGH>;
  };
  pinctrl_nce: nce{
   fsl,pins = <
    SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0
    SC_P_ESAI0_TX1_LSIO_GPIO0_IO05   0xE6000020 /* gpio 485 nCE   in-out, pull-up, high-drive*/
   >;
   gpios = <&gpio0 5 GPIO_ACTIVE_HIGH>;
  };
  pinctrl_trgoe: trgoe{
   fsl,pins = <
    SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0
    SC_P_ESAI0_TX2_RX3_LSIO_GPIO0_IO06  0xE6000020 /* gpio 486 TRGOE  in-out, pull-up, high-drive*/
   >;
   gpios = <&gpio0 6 GPIO_ACTIVE_HIGH>;
  };
 };
};‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Following the example from the aforementioned thread, I added in the line "SC_P_COMP_CTL_GPIO_1V8_3V3_GPIORHB_PAD 0x000514a0" for each GPIO.  My question is if I can change the output voltage by somehow modifying the hex value at the end of the line.

Any help appreciated.  Thanks!

Nolan Z

[igorpadykov]

Hi Nolan

>question is if I can change the output voltage by somehow modifying the hex value at the end of the line.

unfortunately not, it can be changed from userspace:

MX8 GPIO - Variscite Wiki 

Best regards
igor
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