USB port

[VincentChou1z]

Hi!  All,

We are working on a new design based on i.MX53QSB.  I have one question regarding USB ports.  There are one USB OTG and one USB Host port on i.MX53 chips as well as the QSB.  However, QSB specifically design the board not to allow both USB ports to be connected in the same time.  Does anyone know there are any issues inside USB ports of i.MX53 we have to avoid?  We would like to prevent any drawback as early as possible.  Any suggestion is well appreciated!

Vincent

[VincentChou1z]

Hi! Scott,

It has been some time!  I wonder freescale has fixed this bug or not.  Do you have any update on that?  How about changing OTG into USB Device only?  Is this kind of a workaround for that?  Any suggestion is appreciated!

Vincent

[ken_sun-b03826]

Hi Vincent,

could you describe the bug a little detail?

OTG in MX53 can be configured as Host only or Device only, base on the ID value.

Ken

[drscott]

Chou,

We have briefly looked at the OTG bug - lots of interconnected sub-system driver pieces to wade through before the bug source is located.  Therefore we are testing a few other platforms (first one will be gumstik TI3530) we have laying around to see if these work to perhaps do differential code checking to determine the source of the problem.  Anything USB is difficult to troubleshoot and OTG just adds more layers of difficulty...I'll keep you informed.  We have expertise here with host USB but little in OTG so we're learning as we go.

Scott

[VincentChou1z]

Hi! Scott,

Thanks for the info!  Do you know the OTG bug will be fixed in the future or not?  Any way to fix it by ourselve?  Thanks for the info anyway!

Vincent

[drscott]

The 'middle' USB type A port is a traditional host USB and we typically will have this port connected to a hub for mouse/keyboard support (and/or thumb drive connection).  The "bottom" type A connection is also parallel connected to the usb otg connection - they are not independent!  To use OTG, you need to modprobe one of the three otg drivers (g_ether, g_file_storage, g_serial).  We have 'successfully' tried both the g_ether and g_file_storage drivers.  One word of caution; there is a bug in OTG support in general with the BSP - you cannot unplug and re-plug the usb cable and maintain otg support...hope this helps.

Scott

[VincentChou1z]

Hi! Vladan,

I revisited the schematic of SMD and QSB.  I discovered both use USB OTG and USB HS1 only.  I do know they want to save cost to build these two designs.  If we add two USB PHY to attach two additional USB socket to the platforms, is there going to be a performance bottleneck on the CPU end?  What would be the PHY you may prefer?  USB3317?  Also, Is it better to use multiple USB ports in i.MX53 instead of adding a USB hub if multiple USB devices are required in the design?

Vincent 

[VincentChou1z]

Ok!  Got it!  Thanks a lot!  By the way, if I want to utilize all 4 USB ports, what would be the interface I may need to sacrifice?  I probably need to add two additional USB PHY as well.  Am I right?

[VladanJovanovic]

Let's be precise first: on i.MX53 there's one USB OTG and three USB host ports. There's no reason why you couldn't use all of them at the same time.

However, i.MX53 quick start board design is such that signals from USB OTG controller are connected to two connectors - one is micro USB and other is host connector. Naturally, you can't use these two at the same time. You can use other host controller on i.MX53QSB (connected to USB HOST 1) at the same time with USB OTG, no issue with that.