OTG Test
From ESS-WIKI
If you are using RSB-4220, please test it as follows:
Connect 1 and 2 on cn25
If you want to test the slave mode, please execute the following instructions：
echo "peripheral" > /sys/devices/platform/ocp/47400000.usb/47401400.usb/musb-hdrc.0.auto/mode
If you want to test the host mode, please execute the following instructions：
echo "host" > /sys/devices/platform/ocp/47400000.usb/47401400.usb/musb-hdrc.0.auto/mode