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Configuring USB Ports in Mecha Hardware

In this tutorial, we'll walk through the steps to check and set the modes of the USB ports on Mecha hardware, which has two Type-A USB ports that can be configured as either host or gadget modes using sysfs entries. By default, USB-1 (J214) operates in gadget mode, and USB-2 (J213) operates in host mode.

1. Check the Current Mode of USB Ports​

Before making any changes, it's important to know the current mode of the USB ports. You can do this by reading the role file for each port in the sysfs.

Check Mode for USB-1 (J214):

cat /sys/class/udc/ci_hdrc.0/device/role

Check Mode for USB-2 (J213):

cat /sys/class/udc/ci_hdrc.1/device/role

These commands will output either host or gadget, indicating the current mode of each USB port.

2. Set Host Mode for USB Ports​

If you want to configure the USB ports to operate as a host, you can set the role to host. This mode allows the USB port to control other devices (e.g., USB drives, keyboards).

Set Host Mode for USB-1 (J214):

echo host > /sys/class/udc/ci_hdrc.0/device/role

Set Host Mode for USB-2 (J213):

echo host > /sys/class/udc/ci_hdrc.1/device/role

After running these commands, the USB ports will be switched to host mode.

3. Set Gadget Mode for USB Ports​

To switch the USB ports to gadget mode, where they can act as USB devices (e.g., appearing as storage devices or network interfaces when connected to a host), set the role to gadget.

Set Gadget Mode for USB-1 (J214):

echo gadget > /sys/class/udc/ci_hdrc.0/device/role

Set Gadget Mode for USB-2 (J213):

echo gadget > /sys/class/udc/ci_hdrc.1/device/role

After these commands, the USB ports will function in gadget mode.

4. Verify the Changes​

After setting the modes, it's a good practice to verify that the changes have taken effect.

Verify Mode for USB-1 (J214):

cat /sys/class/udc/ci_hdrc.0/device/role

Verify Mode for USB-2 (J213):

cat /sys/class/udc/ci_hdrc.1/device/role

The output should reflect the new mode (host or gadget) based on the changes you made.

How to use USB on Linux machine​

1. Plug in the USB Device​

Insert the USB device into a USB port on your Linux machine.

2. Check if the USB Device is Detected​

Open a terminal and type the following command to list all connected storage devices:

lsblk

This will display a list of all block devices. Look for your USB device, typically labeled as /dev/sdX (where X is a letter like a, b, etc.). You can also use:

dmesg | tail

This will show the latest kernel messages, which should include information about the connected USB device.

3. Create a Mount Point (if necessary)​

Create a directory where you can mount the USB device, for example:

sudo mkdir /mnt/usb

4. Mount the USB Device​

Mount the USB drive to the directory you just created. Replace /dev/sdX1 with the correct partition (e.g., /dev/sdb1):

sudo mount /dev/sdX1 /mnt/usb

After mounting, you can access the files on the USB drive using:

cd /mnt/usb
ls

5. Access and Manage Files​

You can now copy, move, delete, or edit files on the USB drive using standard Linux commands like cp, mv, rm, etc. Example:

cp /path/to/file /mnt/usb/

6. Safely Unmount the USB Device​

Before removing the USB device, unmount it to ensure that all data is properly written and to avoid file system corruption:

sudo umount /mnt/usb

If you get a "device is busy" error, it means some process is still using the USB device. You can use the lsof command to find out what is using the device:

lsof +f -- /mnt/usb

After resolving the issue, try unmounting again.

7. Remove the USB Device​

Once unmounted, you can safely remove the USB device from the port.

8. Additional Tips​

Formatting the USB Drive​

If you need to format the USB drive, you can use mkfs for various file systems like FAT32, NTFS, or ext4:

sudo mkfs.vfat /dev/sdX1    # For FAT32
sudo mkfs.ntfs /dev/sdX1    # For NTFS
sudo mkfs.ext4 /dev/sdX1    # For ext4

Checking Disk Usage​

To see how much space is used or free on the USB drive:

df -h /mnt/usb

9. Auto-mount USB Devices​

Most modern Linux distributions automatically mount USB devices when plugged in. If this doesn't happen, you can add an entry to the /etc/fstab file for auto-mounting.

Example entry in /etc/fstab:

/dev/sdX1 /mnt/usb <vfat> defaults 0 0

This guide should help you get started with using USB devices on a Linux system, whether you're accessing files, managing partitions, or safely removing the device.