topic Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0 in i.MX Processors

Communicating with external storage SSD with only using RX and TX line of the USB3.0

Parag1 — Thu, 21 Sep 2023 07:54:17 GMT

Hello Team,

I am using imx8m plus processor , and want to connect external storage SSD

Above is the block diagram of the IC i am going to use for the SSD Connection and Communication.
In this IC as you can see both USB3.0 and USB2.0 of the imx8m are connected to the SATA Gen1/2 .
But in my case USB2.0 will not be available we are using it for different application , so only TX and RX pins of the USB3.0 will be there . so will it possible to establish the connection with SSD using only TX and RX pins or do we required DP and DM ?
Please provide your response on this query.

Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0

riteshmpatel — Thu, 21 Sep 2023 11:21:22 GMT

Hi @Parag1,

I hope you are doing well.

DP and DM pins are necessary for USB enumeration and speed detection. So, they cannot be omitted from the USB 3.0 connections.

I hope it helps!

Thanks & Regards,
Ritesh M Patel

Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0

Parag1 — Fri, 22 Sep 2023 06:28:49 GMT

Hello Ritesh,

Thank you or the Response,

What i think USB3.0 will Use Rx and TX first for the USB enumeration and speed detection, then it will switch to DP and DM if RX and Tx are busy .So it may possible to communicate with Rx and Tx lines of USB3.0 between imx8m and SSD.
Please let me know if i am wrong

Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0

riteshmpatel — Fri, 22 Sep 2023 10:46:29 GMT

Hi @Parag1,

Apologies for the inconvenience caused.
I discussed this with my internal team. Please see the response below:

DP/DM is used for USB 2.0. Normally, to make it compatible with USB 2.0. DP/DM, SS_Txp/Txn, and SS_Rxp/Rxn will be connected to the same port. That is DP/DM is not used in super-speed communication.

Thanks & Regards,
Ritesh M Patel

Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0

Parag1 — Fri, 22 Sep 2023 12:51:49 GMT

Hi Ritesh,

Thank you for the clarification

I need to confirm one thing , are there different USB2.0 PHY and USB3.0 PHY ?or the single USB PHY which controlled both USB2.0 and USB3.0?
Basically i am uing USB2.0 for the flashing and debugging and USB3.0 Rx and Tx for the SSD , so whether both the things can run simultaneously ?

above image is from the imx8m reference manual . here they have mentionUSB2.0 PHy and USB3.0 PHY , so i think there will be different phy for the both ,So according to this i can use USB2.0 for flashing and debugging and USB3.0 for the SSD at the same time.

Please let me know on this topic

Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0

Parag1 — Mon, 25 Sep 2023 07:11:41 GMT

Hi Ritesh,

Can you please quickly update here

Thank you for your support

Re: Communicating with external storage SSD with only using RX and TX line of the USB3.0

riteshmpatel — Tue, 26 Sep 2023 09:21:19 GMT

Hi @Parag1,

USB port cannot be used for debugging. For debugging, one can use the UART port as mentioned in the Reference Manual.

In addition to that, flashing via USB 2.0 and using RX & TX for USB 3.0 cannot happen at the same time, since while flashing the processor, only ROM code will run.

I hope it helps!

Thanks & Regards,
Ritesh M Patel