DART-6UL USB OTG
Configuring the USB1 port under Linux
By default, the USB1 port is configured as host in the device tree, and a USB type-A receptacle is assembled on the VAR-6ULCustomBoard.
To use it as peripheral (OTG is not supported in the VAR-6ULCustomBoard) you need to change the value of the dr_mode property under the usbotg1 node in the device tree, and assemble a USB Micro-AB receptacle at J23 on the bottom of the VAR-6ULCustomBoard.
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/arm/boot/dts/imx6ul-imx6ull-var-dart-common.dtsi
(in very old kernel releases where this file is not available, you should edit arch/arm/boot/dts/imx6ul-var-dart.dtsi instead)
&usbotg1 {
- dr_mode = "host";
+ dr_mode = "peripheral";
disable-over-current;
status = "okay";
};
If you build the kernel manually from source code, you should build only the device trees and copy them to your SD card.
Note: You can read the current dr_mode value on a running target, by executing the following command:
# cat /sys/firmware/devicetree/base/soc/aips-bus@02100000/usb@02184000/dr_mode; echo
Using the USB1 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.
Example using the g_mass_storage module to expose the BOOT partition on our recovery SD card to a PC:
Connect a micro-B plug to Standard-A plug cable between the board and a PC, and run the following on the board:
# umount /dev/mmcblk0p1 # modprobe g_mass_storage file=/dev/mmcblk0p1
The partition should be loaded on the PC as a mass storage device.