• State TI Thinks Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 2 answers
  • Subscribers 30 subscribers
  • Views 222 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCM2704C: Whether the USB bus is working in UXB2.0 or USB1.1 state

Alan Xia
Expert 4415 points
Part Number: PCM2704C
Other Parts Discussed in Thread: PCM2704,

Hi team，

Customers encountered problems when using this chip to transmit audio, and felt that the entire usb2.0 bus was pulled down to usb1.1 mode.

Need to confirm whether it is working in usb2.0 mode or in usb1.1?

  • 0
    TI__Genius 11210 points

    Hi Alan,

    USB 2.0 and USB 1.1 are compatible in the sense that they share the same port connection, what the datasheet is outlining is that the descriptors provided to host are in USB 1.1 format (9.5 of d/s). The audio will not change for either USB because both bits/sampling rates are supported

  • 0 in reply to Daveon Douglas
    TI__Expert 4415 points

    Hi Daveon，

    The customer is using a usb hub, and 12 PCM2704Cs are connected to one of the usbs. When using it, I found that only 8 channels can be used at the same time. There was a problem when the 9th channel was turned on. Later they calculated that the 8th channel just reached the upper limit of usb1.1.

    Now the customer thinks that it is usb1.1 that pcm2704 is working on, so the whole usb can only work in usb1.1 mode, resulting in the speed not reaching.

  • 0 in reply to Alan Xia
    TI__Expert 4415 points

    By the way,Is there any way for us to know whether the USB port is in USB2.0 or USB1.1.

  • 0 in reply to Alan Xia
    TI__Genius 11210 points

    Hi Alan,

    To my knowledge USB2.0 and USB1.1 cables are the same, the only difference would be the specifications of the devices (i.e how fast data is transferred). PCM2704 is a USB2.0 device and if the USB HUB is a USB2.0 device, USB2.0 is the mode of operation.

    If the USB HUB is not recognizing 4 PCM27xx devices, is it 4 together like I highlighted below or clustered as shown in red X's? From here I would troubleshoot disconnecting devices to see if this is a limitation of the HUB. I would also check the clocking specifications of the main USBHUB to make sure it can support as well

  • 0 in reply to Daveon Douglas
    TI__Expert 4415 points

    Hi Daveon,

    My customer directly connects PCM2704C to the OTG port of IMX8, and finds that PCM2704C will be recognized as a USB1.1 device.

    Customers have a lot of doubts about this, PCM2704C should be a 2.0 device, do you need to do some settings?

  • 0 in reply to Alan Xia
    TI__Genius 11210 points

    Hi Alan,

    This is because the descriptors for the IC is USB 1.1 format, but it will still execute USB2.0 performance as expected.

  • 0 in reply to Daveon Douglas
    TI__Expert 4415 points

    Hi Daveon，

    1、The customer said that if the descriptor recognized by the system is in USB1.1 format, the system will automatically limit the bandwidth of the device to USB1.1, making it unable to run on USB2.0. Is this part a system that can only be modified by the client area?

    2、Can PCM2704C support the expansion of one USB channel to more than 8 channels? 12 channels?

  • 0 in reply to Daveon Douglas
    TI__Expert 4415 points

    Does TI have devices with USB2.0 descriptors?

  • 0 in reply to Alan Xia
    TI__Genius 11210 points

    Hi Alan,

    Unfortunately our portfolio of USB audio converters/DACs is very limited, PCM270(4/6)c are the only devices that are compliant with USB2.0 specification. Since the descriptors of USB bus is 1.1 the host controller may be limiting bandwidth like customer suspects due to this.

    I would try testing a third party USB2.0 device to see if this truly is a descriptor/HUB issue or the HUB is not performing as expected