Peripheral Adaptation

"CAM-CRV1126S2U/CAM-C1109S2U" retains a wealth of expansion
interfaces, including "Ethernet", "USB", "Serial port", "GPIO", "I2C",
"I2S", "SPI", "SDIO", etc. Basically meet all the expansion needs of
customers. This chapter mainly describes some simple peripherals that
may be used by the gates.


Relay

The essence of the relay is to operate " GPIO", here is how to operate
" GPIO" in the system.

Check the interface definition and select the  GPIO to be manipulated,
such as  GPIO3_D6

Calculate GPIO number

   # GPIO3_D6
   3 x 32 + 3 x 8 + 6 = 126
   # Formula GPIO(X)_(Y)(Z)
   # Where the variable Y ：A = 0，B = 1，C = 2，D = 3
   X x 32 + Y x 8 + Z

Register GPIO

   echo 126 > /sys/class/gpio/export

   # Need to confirm that the GPIO is not occupied and not initialized other functions
   # If GPIO3_D6 is also the I2S_m0 port, I2S needs to be disabled in the kernel
   vim sdk/kernel/arch/arm/boot/dts/rv1109-firefly-ai-cam.dts (rv1126-firefly-ai-cam.dts)
   # Add the following code at the end
   &i2s0 {
   	status = "disabled";
   };
   # Compile and upgrade the kernel

Set GPIO to output mode

   echo out > /sys/class/gpio/gpio126/direction

Set GPIO output high/low level

   echo 1 > /sys/class/gpio/gpio126/value # high level
   echo 0 > /sys/class/gpio/gpio126/value # low level

LED

Select the GPIO port, modify the kernel device tree, and add a custom
LED device node.

   vim sdk/kernel/arch/arm/boot/dts/rv1109-firefly-ai-cam.dts (rv1126-firefly-ai-cam.dts)
   # Refer to the following configuration to add LED nodes.
    leds {
       compatible = "gpio-leds";

       user_led: user {
           label = "firefly:yellow:user";
           linux,default-trigger = "ir-user-click";
           default-state = "off";
           gpios = <&gpio3 RK_PD6 GPIO_ACTIVE_HIGH>;
           pinctrl-names = "default";
           pinctrl-0 = <&led_user>;
       };
   };

   # pinctrl needs to add GPIO multiplexing control
   led_user: led-user {
   	rockchip,pins = <3 RK_PD6 RK_FUNC_GPIO &pcfg_pull_none>;
   };

   # Compile and upgrade the kernel after modification

Control LED

   echo 1 > /sys/class/leds/firefly:yellow:user/brightness # Light up
   echo 0 > /sys/class/leds/firefly:yellow:user/brightness # Light off