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[kiyoshi]

We are conducting a USB Compliance test on a custom board with a Toradex module for our customer.

We are discussing whether this is a problem because the USB SSTX is outputting some signal all the time even though there is no other device connected to it, and we do not know what happens.

When we checked with Toradex, they replied that all of their SoC-based products (and your BSP) have the same behavior, so Toradex does not know what is going on.

Is the above behavior actually within the scope of the specifications?

We would appreciate it if you could provide us with some clarification.

Subject product: Apalis iMX8 QuadMax 4GB Wi-Fi / Bluetooth IT

PN: 0037

https://www.toradex.com/ja-jp/computer-on-modules/apalis-arm-family/nxp-imx-8?_gl=1%2A2d4ypx%2A_up%2...

Please download the documents from the following URL.

◇Link URL

https://link.directcloud.jp/kjqbm9Co1u

◇password

EA7T84IC

Thank you for your cooperation.

[Rita_Wang]

Which product are you using?

[alvaro_tx]

MIMX8QM6AVUFFAx

[Rita_Wang]

We have the AN here I can share to you https://www.nxp.com/docs/en/application-note/AN12409.pdf

[alvaro_tx]

Hi Rita, the question is not related to USB compliance setup but about how the USBH4_SSTX signal is outputting pulses while no USB device connected to it. 

Please find a video here: https://share.toradex.com/sh0019vd2vy585v

As you can see, as the kernel (imx 5.15) boot, the blue signal (USBH4_SSTX_N) is all over the place. We have no idea why. According to the USB 3.0 specification, there should be no activity in the SSTX as long as there is no device connected. 

We have made no changes to the USB Drivers and there are no downstream devices connected to USBH4, just a USB 3.0 connector. 

[Rita_Wang]

How about your USBH4_SSTX_N design, I do not see in our reference design. Or can you share us your design schematic to us, for just the video it is hardly to know what is the root cause.

[alvaro_tx]

My hope was that you could confirm this phenomenon in NXP iMX8 EVK as we don't have one here. 

Our USBH4 design is essentially some overvoltage protections and the connector directly from the SOM/SOC. 

[Rita_Wang]

Hi @alvaro_tx @kiyoshi ,

I will take two week sick day leave, so for your update I maybe can not follow, sorry about it. I already ask for help to my colleague Joan she have more experience, she will give support to you. I help create new case 00620541 to her, do not worry we will support you. Thanks a lot for your kindly understandings

Keep happy and health

Wish you have a nice day

Best Regard

Rita

[alvaro_tx]

Dear @Rita_Wang @joanxie , any update in this matter? Thanks a lot 

[Rita_Wang]

@alvaro_tx Please update in the 00620541, Joan will following it there. Thanks

[alvaro_tx]

Sorry @Rita_Wang but what is 00620541? How can I check its updates?

[Rita_Wang]

@alvaro_tx For the @kiyoshi can receive the email from the case, you can ask him to add you,

As you can see, as the kernel (imx 5.15) boot, the blue signal (USBH4_SSTX_N) is all over the place. 

>what blue signal do you mean? pls show me again, and I don't find this pins from nxp lpddr4 board, which detailed pin do you mean? maybe you use the third party company board, I need to know which pin in nxp board you mentioned

For this, @kiyoshi do not give the update to us in the case.

[alvaro_tx]

Hi @Rita_Wang 

The signals in the NXP iMX8QM EVK are USB_SS3_TX_N (B32) and USB3_MUX_TX_P (A33)

I believe these signals go to the USB Type C connector DX07S024JJ2R1300 (J17) as SS_TX1_P and SS_TX1_N after going to U36 and U38 (protection and level shifter). 

Alvaro.