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Original question:

CCS/TM4C129XNCZAD: TM4C129 device USB is not working

CCS/TM4C129XNCZAD: TM4C129XN USB not working properly

Mourad Jelili
Prodigy 180 points
Part Number: TM4C129XNCZAD

Tool/software: Code Composer Studio

Dear Sir,

We have an issue with TM4C129XN USB not working properly with Michrochip USB HUB part number USB2512.  Here is the details of the trace:

from our USB HUB expert below : 
=============================================================================================== Details
If you open the trace and scroll to the bottom, you will see the problem. 

This host is attempting to INITIATE communication with a Complete Split packet. You cannot do that. 
Every SPLIT transaction must start with a Start Split packet, then to complete the transaction, a follow up Complete Split packet is sent. 

You cannot start a transaction with a Complete SPLIT. That is why the device is sending a STALL. 
Please find herewith an internal Microchip training document which explains SPLIT transactions. 
===============================================================================================

Microchip has answered as follow:

Based on the log that you provided to use we can confirm an unproper handling from the HOST transactions in the USB HOST processor stack. 
the log shows that there is no issue with our HUB device.It reacts as expected by the USB protocole. 
You need to correct the USB HOST stack in order to follow the USB protocole. 
As this is not a Microchip processor / USB HOST processor stack, you'll need to get TI support on this to fix the SPLIT transactions 

========================================================

Could you please help what other alternatives/options/solution to fix this issue? Is there anything in USB Hub configuration that can fix this issue? Thanks

Kind regards,
Mourad

  • 0
    TI__Guru 72500 points
    Would you please describe what hardware (custom board or TI Launchpad) you are using and what software is programmed into the TM4C129 device?
  • 0
    TI__Guru 72500 points
    See this post about USBLIB and split transactions:
    e2e.ti.com/.../2789359
  • 0 in reply to Bob Crosby
    Prodigy 180 points
    Hi Bob,
    Thank you.
    Is not TI going to implement SPLIT transaction to use the USB Host stack? Normally it’s part of USB standard. If not, is it easy to implement? Is there any example of code or configuration to add this function?
    What other options we have TI fix the design? Many thanks
    Regards,
    Mourad
  • 0 in reply to Mourad Jelili
    TI__Guru*** 128155 points
    Hello Mourad,

    We do not have any plans to support SPLIT transactions for the USB stack and have not done any assessment to the ease or difficulty to implement this feature.

    It simply has not come up enough to warrant further investigation from our end as this is only the second case I am aware of.

    If there continues to be a trend for needing this feature, we may re-assess that stance in the future, but as of now there are no plans to support SPLIT transactions.
  • 0 in reply to Ralph Jacobi
    Prodigy 180 points
    Hello Ralph,

    Thank you for message.

    The thing that I have already designed PCB based on HUB circuit and we are in phase of re-spin of PCB to take a decision to go in production. Your answer does not left me an option. Is there any other TI MCU with this feature implemented?
    There is a case an old one "how to generate a split start packet and a split complete packet" related to split for USB packet, is it the same issue?

    Kind regards
    Mourad
  • 0 in reply to Mourad Jelili
    TI__Guru*** 128155 points
    Hello Mourad,

    I am only an expert on TM4C devices so I am not aware what support is available on other TI MCU's. There are definitely MSP430 devices with USB support but whether they support SPLIT transactions is not knowledge I have.

    Those two packets I referred to are the basis of a SPLIT transaction per USB standard. To have SPLIT transaction support, you must have support for those two types of packets implemented.