Linux USB OTG: Difference between revisions
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For example, there is an Ethernet gadget module called g_ether, a mass storage gadget called g_mass_storage, a serial gadget called g_serial, etc.<br> | For example, there is an Ethernet gadget module called g_ether, a mass storage gadget called g_mass_storage, a serial gadget called g_serial, etc.<br> | ||
<br> | <br> | ||
===Examples=== | |||
Connect a type-C plug to Standard-A plug cable between the board and a PC, and run the following on the board: | |||
Connect a type-C plug to Standard-A plug cable between the board and a host PC, and run the following examples on the target board: | |||
==== Mass Storage Device ==== | |||
The following uses the g_mass_storage module to expose the root partition on eMMC to a PC while booting from recovery SD card:<br> | |||
# umount /dev/{{#var:EMMC_ROOTFS_DEV}}p1 | # umount /dev/{{#var:EMMC_ROOTFS_DEV}}p1 | ||
# modprobe g_mass_storage file=/dev/{{#var:EMMC_ROOTFS_DEV}}p1 | # modprobe g_mass_storage file=/dev/{{#var:EMMC_ROOTFS_DEV}}p1 | ||
The partition should be loaded on the PC as a mass storage device. | The partition should be loaded on the PC as a mass storage device. | ||
==== USB Debug Console ==== | |||
The following uses the g_serial module to spawn a new debug console over USB: | |||
On target: | |||
# echo g_serial > /etc/modules-load.d/g_serial.conf | |||
# sudo systemctl enable getty@ttyGS0.service | |||
# reboot | |||
On Host: | |||
$ minicom -D /dev/ttyACM0 | |||
}} | }} | ||
Revision as of 19:56, 9 June 2022
Configuring the USB OTG port under Linux
By default, the USB OTG port is configured as OTG in the device tree, and a USB type-C receptacle is assembled on the DART-MX8M custom board.
To use it as host only or peripheral only you need to change the value of the dr_mode property under the USB node in the device tree.
dr_mode: One of "host", "peripheral" or "otg". Defaults to "otg"
For example:
Follow either the "Build the Linux kernel from source code" or "Customizing the Linux kernel" Wiki pages and edit the following device tree file:
arch/arm64/boot/dts/freescale/fsl-imx8mq-var-dart-common.dtsi
&usb_dwc3_0 {
status = "okay";
extcon = <&typec_ptn5150>;
- dr_mode = "otg";
+ dr_mode = "host";
};
If you build the kernel manually from source code, you should build only the device trees and copy them to your SD card or eMMC.
Note: You can read the current dr_mode value on a running target, by executing the following command:
# cat /sys/firmware/devicetree/base/usb@38100000/dwc3/dr_mode;
Using the USB OTG port under Linux
As host (default)
As peripheral
In order to use the board as a peripheral, an appropriate module needs to be loaded.
For example, there is an Ethernet gadget module called g_ether, a mass storage gadget called g_mass_storage, a serial gadget called g_serial, etc.
Examples
Connect a type-C plug to Standard-A plug cable between the board and a host PC, and run the following examples on the target board:
Mass Storage Device
The following uses the g_mass_storage module to expose the root partition on eMMC to a PC while booting from recovery SD card:
# umount /dev/mmcblk0p1 # modprobe g_mass_storage file=/dev/mmcblk0p1
The partition should be loaded on the PC as a mass storage device.
USB Debug Console
The following uses the g_serial module to spawn a new debug console over USB:
On target:
# echo g_serial > /etc/modules-load.d/g_serial.conf # sudo systemctl enable getty@ttyGS0.service # reboot
On Host:
$ minicom -D /dev/ttyACM0
As OTG
With OTG, the board can be either a host, or a peripheral.
In order to use it as a host and connect a peripheral (e.g. a USB flash drive) to it, either use a peripheral with type-C connector or use type-C to type-A adapter.
In order to use it as a peripheral and connect it to a PC, for example, a cable with a type-C plug on one end and a Standard-A plug on the other is needed.