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Does the architecture of the Compute Module (when mounted in a Compute Module IO Board) support simultaneous USB host and device/client port operation? This post suggests that a BeagleBlack Bone board is more suitable (because previous RPi only allowed host or device, but not both at the same time).

As a simple experiment, I tried connecting the USB host port to the slave port on the CMIO board (via a hub that also had a wi-fi adapter)-- this seemed to disrupt the entire USB (disconnecting all devices) until the slave port was disconnected.

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jhfrontz
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No it does not unfortunately. The client mode is only used when flashing the eMMC with a new image. When Linux has booted normally there is USB hos only.

Ronny Nilsson
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  • Right, but is that because of an architectural limitation or because an appropriate driver/configuration isn't in place? – jhfrontz May 07 '15 at 12:43
  • To my knowledge it's architectural. OTG controllers act either as host OR device. You haven't said what you wan't to achieve, but if it's to connect RPi to a PC I can recommend a USB Null modem cable:
    http://www.ftdichip.com/Products/Cables/USBtoUSB.htm Works for host-to-host connections.     – Ronny Nilsson May 07 '15 at 16:18
  • Something I read made me think that only one of the ports was OTG and that the other was a pure device port-- I guess maybe that's the question: does the Broadcom SoC on the RPi CM have a single USB bus or are there two? – jhfrontz May 07 '15 at 20:28
  • There is a single USB port only. – Ronny Nilsson May 07 '15 at 21:07
  • On the compute module IO board there are two physical USB connectors (in the pic at https://www.raspberrypi.org/wp-content/uploads/2014/06/cm-devkit-boards-500x287.jpg, one a host at center bottom and one a device "slave" at bottom left). Are you saying that they are the same USB port? – jhfrontz May 08 '15 at 20:10
  • Yes, it's the same (logical) USB port. There is a switch in the board to mux the two physical connectors. If you want to know the details it can be seen in the HW schematic available at raspberrypi.org – Ronny Nilsson May 08 '15 at 22:31
  • Aha, found it at the bottom of https://www.raspberrypi.org/wp-content/uploads/2014/04/RPI-CMIO-V1_2-SCHEMATIC.pdf. tnx. – jhfrontz May 12 '15 at 05:21