A388 base control RESET# on M.2 bus

ARMADA A388
1

How do we control the I2C_IO_1_2 and I2C_IO_0_2 signals via U19 PCA9655 to the M.2 connector from userspace or via C code?

2

Can someone from SolidRun please reply? Anyone? It has been more than a month.

3

Controlling U19 IO-Expander on I2C Bus-0 at Address 0x20

The U19 IO-Expander is connected to I2C bus-0 at address 0x20. Below are the three methods to control its GPIOs:

1. Configure GPIO in DTS

  • Define the GPIO in the Device Tree (DTS) for kernel-level configuration.
  • Refer to the example from the Armada Clearfog DTS file.Example DTS node:
expander0: gpio-expander@20 {
    compatible = "nxp,pca9555";
    gpio-controller;
    #gpio-cells = <2>;
    reg = <0x20>;
};

2. Control GPIOs Using GPIOLib or Sysfs

If the IO expander GPIOs are not pre-configured in the DTS, you can manage them from user space:

a. Determine GPIO Base Offset

  • The GPIO base offset is assigned dynamically. To find it:
ls /sys/class/gpio/

Example output:

export       gpiochip0    gpiochip32   gpiochip496  unexport
  • In this example, gpiochip496 corresponds to the IO expander base.
  • Calculate GPIO numbers for individual pins:
    • I2C_IO_0_2: GPIO = 496 + 0*8 + 2 = 498
    • I2C_IO_1_2: GPIO = 496 + 1*8 + 2 = 506

b. Control GPIOs Using Sysfs

  1. Export the GPIO:
echo 498 > /sys/class/gpio/export
  1. Configure direction and value:
echo out > /sys/class/gpio/gpio498/direction
echo 1 > /sys/class/gpio/gpio498/value  # Set HIGH
echo 0 > /sys/class/gpio/gpio498/value  # Set LOW

c. Control GPIOs Using GPIOLib Utilities

use the gpiolist command to find the correct gpio class name for the IO_Exapnder (for example gpiochip496 or expander0…)

  • Use the gpioset command for modern kernels with GPIOLib support:
gpioset gpiochip496 2=1  # Set I2C_IO_0_2 HIGH
gpioset gpiochip496 2=0  # Set I2C_IO_0_2 LOW
gpioset gpiochip496 10=1 # Set I2C_IO_1_2 HIGH
gpioset gpiochip496 10=0 # Set I2C_IO_1_2 LOW

**3. Force GPIO Values Using I2C-Utils **

Note This also works when the GPIO is defined in the Device Tree (DTS)

You can directly modify the IO expander’s register values using i2c-utils.

a. Install i2c-utils

sudo apt update
sudo apt install i2c-tools

b. Modify Registers

  • Use the PCA9655 datasheet Page 9-10 to locate the direction and value registers.
  • Example commands:
    • Set direction:
i2cset -y 0 0x20 0x06 0xFB  # Set pin 2 of port 0 as output
  • Set output value:
i2cset -y 0 0x20 0x02 0x04  # Set pin 2 HIGH
i2cset -y 0 0x20 0x02 0x00  # Set pin 2 LOW

Summary

  • DTS Configuration: Best for kernel-managed GPIOs.
  • GPIOLib/Sysfs: Allows user-space control without kernel changes.
  • I2C-Utils: Provides direct hardware access for fine-grained control.
4

All of the methods provided report “Resource busy”:

root@OpenWrt:/# echo 498 > /sys/class/gpio/export
ash: write error: Resource busy
root@OpenWrt:/# i2cset -y 0 0x20 0x06 0xFB
Error: Could not set address to 0x20: Resource busy

5

can you run rfkill list and post the results?

6

How do I add rfkill to openwrt?