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EK-TM4C1294XL: USB 2.0 only with ext. PHY?

Part Number: EK-TM4C1294XL
Other Parts Discussed in Thread: TPS2052B, TM4C1294NCPDT

Hi all,


I am a bit confused. The SPMU365C_EK-TM4C1294XL_Users Guide says:


"2.1.3 USB Connectivity
The Connected LaunchPad is designed to be USB 2.0 ready. A TPS2052B load switch is connected to and controlled by the microcontroller USB peripheral, which manages power to the USB micro A/B connector when functioning in a USB host. When functioning as a USB device, the entire Connected LaunchPad can be powered directly from the USB micro A/B connector. Use JP1 to select the desired power source. USB 2.0 functionality is provided and supported directly out of the box with the target USB micro A/B connector. High-speed USB 3.0 functionality can be enabled by adding an external USB PHY. The USB external PHY control and data signals are provided on the breadboard expansion header X11."


But the SPMS386C_TM4C1294NCPDT_Microcontroller_Datasheet says:

"The TM4C1294NCPDT USB module has the following features:
...
USB 2.0 high-speed (480 Mbps) operation with the integrated ULPI interface communicating
with an external PHY
..."

I'm wondering which datasheet contains the correct information?

I set up a TIRTOS USB firmware together with the USBCDCD driver. On the host I run a small Qt console application to determine the average triptime of 64 byte dummy data blocks. The ping pong works fine but the traffic is very slow (~700kB/s).
The device descriptor for the Virtual COM Port contains "USB Spec 1.1" in the bcdUSB field (determined with USBlyzer). For me it seems, as if the SPMS386C_TM4C1294NCPDT_Microcontroller_Datasheet contains the correct information. USB 2.0 is only working with the ext. PHY.

Am I right? If yes, does it also work with a ext. PHY for USB 3.0? If not, what am I doing wrong not beeing able to establish a USB 2.0 connection?

Thanks for your answer(s).

Regards, Miguel

  • The datasheet is correct as far as I am aware. There's no support for USB 3.0 on the TM4C series. They support USB 2.0 (15Mbps) with the internal PHY, but to get 480Mbps you need an external PHY such as TUSB1210BRHBR connected by ULPI.
  • Hello Miguel,

    The answer is both contain correct information.

    The datasheet of TM4C1294NCPDT is the official device datasheet, that is correct and accurate regarding the silicon in question.

    Now then to be clear on this next part: the SPMU365C document is not a datasheet!! It is a User Guide for the EK-TM4C1294XL LaunchPad to describe the features the LaunchPad can demonstrated based on how it was built. There is a big difference in terms with that, at least from our perspective, and it would be irresponsible to myself to acknowledge SPMU365C as a 'device datasheet'.

    With that said, the SPMU365C User's Guide is accurate about USB 2.0 as well. Note that the User's Guide does not list of a specification for speed capable with USB 2.0, but just calls out the LaunchPad as being USB 2.0 compliant, with no mention of high speed.

    This is because a device can be USB 2.0 compliant without being high speed.

    This mentioned in another line also from TM4C1294NCPDT datasheet: "USB 2.0 Controller OTG/Host/Device with optional high speed using external PHY through ULPI interface"

    This is where the LaunchPad statement of being USB 2.0 Compliant can be made, while still not natively supporting high speed with the hardware on it.

    Sorry you were mislead, but the 'devil is in the details' at times.
  • Hello Matt,

    thanks for your answer. It was partially helpful. There is still one aspect that is not clear to me. As mentioned above, USBlyzer shows a connected USB 1.1 device. Is there a certain register I have to set to change from USB 1.1 to USB 2.0 (15Mbps)?

    Best Regards, Miguel
  • Hello Ralph,

    thanks for your answer. Many things are clearer now. So what you're saying is, that the Users Guide (SPMU365C) is also correct and therefore it's even possible to connect an external USB 3.0 compliant PHY through ULPI interface?

    Exist any reference designs and code examples for external USB 2.0 (high speed) or USB 3.0?

    Best Regards, Miguel
  • Hi Miguel

    There is a reference design for USB 2.0 high speed: http://www.ti.com/tool/TIDM-TM4C129USBHS

    Somebody may have a USB 3.0 PHY that supports ULPI, but ULPI only supports USB 2.0 High Speed data rate anyways so I'm not sure what benefit you get. I believe the User's Guide SPMU365C is in error in mentioning USB 3.0.

    Matt

  • Hello Miguel,

    Not sure which example you are using as well as which port you are using (ICDI vs Target USB) which is reporting the USB 1.1. My first guess is that may be an application thing. I can look into it more if you give me details on how to replicate your setup.

    As far as PHY's for high speed USB 2.0, the following TI design is available for reference: 

    USB 3.0 (super speed) is not supported by the TM4C devices. Only USB 2.0 High Speed.

  • Hi Matt,

    thanks for your answer. This is what I was looking for.

    Best Regards, Miguel