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How to use the USB On The Go (OTG) port of the Armadeus boards under Linux.


The USB OTG feature allows you to use the USB Mini-AB connector of your APFDev board to connect at any time a USB device (by acting as a USB Host) or to connect your system to your Host PC and be seen as a USB device (gadget). OTG is automatically doing the right mode selection depending on the cable you are connecting to the APFDev OTG connector. This of course require that the cable your are using is OTG compatible. Otherwise you may end up continuing to force the OTG connector mode manually.


The USB OTG is available on the:

  • APF28Dev board (since revision 2 of the board == with the USB mini-AB connector),
  • APF6Dev

We also have plan to support this feature on the APF51Dev, as soon as some project members can start this development.


In order to activate the OTG mode, no specific mode should be enforced by the U-Boot otg_mode bootargs parameter:

 BIOS> setenv extrabootargs
 BIOS> saveenv
 BIOS> boot

Your port is now ready to act as an USB OTG connector under linux. Once you have loaded your preferred gadget driver, you are ready to connect and use at any time an USB device or a host PC without rebooting the board to use the USB OTG feature.

Known issues

You can use USB mini A male - USB A female adapter to connect regular USB peripherals to your board with the following limitation:

  • Connect first the USB device to the adaptor before connecting them to the board.
  • Disconnect first the adapter from the board instead of disconnecting the USB device from the adapter.

This is a limitation of current implementation on the 2.6.35 linux USB drivers