GPIO3_B0 to GPIO3_C3 always reads 0 on Luckfox Pico Pro/Max (even as input)

• Soheil_Jbbr

  Posts: 4

  Joined: 2025-12-31 5:15

  2025-12-31 5:28

  Hello Luckfox team and community,
  
  I am trying to use GPIO3_B0 ~ GPIO3_C3 pins as input on a Luckfox Pico Pro/Max (RV1106).
  
  I understand that GPIO3_B0 to GPIO3_C3 are input-only and cannot be used as output. My question is specifically about reading their input value.
  
  What I observe
  

  • The pins measure about 0.8 V when floating
    
    When I externally drive them with 1.8 V, the voltage level changes correctly on the pin
    
    However, Linux always reports the value as 0

  Example:
  
  root@rv1106:~# cat /sys/class/gpio/gpio115/direction
  in
  root@rv1106:~# cat /sys/class/gpio/gpio115/value
  0
  
  What I have already tried
  
  1.Removed pinctrl ownership by commenting out MIPI/LVDS pinctrl:
  
  &rkcif_mipi_lvds {
  pinctrl-0 = <>;
  };
  
  
  2.Disabled the full MIPI / ISP / CIF pipeline in config/dts_config:
  
  &mipi0_csi2_hw { status = "disabled"; };
  &mipi1_csi2_hw { status = "disabled"; };
  &csi2_dphy_hw { status = "disabled"; };
  &csi2_dphy0 { status = "disabled"; };
  &mipi0_csi2 { status = "disabled"; };
  &rkcif { status = "disabled"; };
  &rkcif_mipi_lvds { status = "disabled"; pinctrl-0 = <>; };
  &rkcif_mipi_lvds_sditf { status = "disabled"; };
  &rkisp { status = "disabled"; };
  &rkisp_vir0 { status = "disabled"; };
  
  
  Recompiled the kernel and reflashed the board
  
  Exported GPIO correctly using Linux sysfs (GPIO numbering verified)
  
  My question
  
  Is commenting out / disabling the MIPI-related pinctrl and nodes sufficient to read GPIO3_Bx / GPIO3_Cx inputs?
  
  Or is there any additional configuration required, such as:
  
  Special IO domain / voltage configuration
  
  Pull-up / pull-down settings
  
  GRF / PMU register configuration
  
  Or a known hardware limitation where these pins cannot be read reliably by GPIO even as inputs?
  
  Any clarification or reference to documentation would be greatly appreciated.
  
  Thank you for your time and support.

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