How many devices can it be connected on AM335x USB I/F?

RY9983

Other Parts Discussed in Thread: DA8XX

Hello.

One of our customer would like to use the AM335x USB I/F.
Their requirement is that USB is used as host.
And, they would like to connect more than twenty USB peripherals via USB hub to AM335x USB I/F.

They are concerned whether it is supported on AM335x.
I confirmed that there are no restriction on AM335x datasheet, TRM and silicon errata like that.
But, they are sensitive about this.

Because it could not be supported on other MPU vendor.
And they had great pains in the past production.
It is most important key point of their processor determining.

In order to dispel the concerns of their:
- Are there any restrictions when many USB devices connect to AM335x host?

Best regards, RY

over 12 years ago

0 Bin Liu over 12 years ago

TI__Guru**** 167581 points

Do you know what kind of USB devices which will be plugged into AM335x host? What type of USB transfer does the device use? How many pipes does each device have?

0 RY9983 over 12 years ago in reply to Bin Liu

Guru 10570 points

Bin-san,
Thank you for your response. I will check about your question.
Before checking, can I confirm following?

Bin Liu said:

Do you know what kind of USB devices which will be plugged into AM335x host?

This means : USB Memory, USB Camera, USB other devices etc.. Right?

Bin Liu said:

What type of USB transfer does the device use?

This means : Control / Bulk / Interrupt / Isochronous transfer. Right?

Best regards, RY

0 Bin Liu over 12 years ago in reply to RY9983

TI__Guru**** 167581 points

yes, those are right.

0 RY9983 over 12 years ago in reply to Bin Liu

Guru 10570 points

Bin-san,
OK. I will get back to you. RY

0 Ravi B over 12 years ago

TI__Expert 7885 points

Unlike in old davinci or da8xx SoCs (which has only 4Tx/Rx endpoints), the AM335x has more eps, 15 Tx and 15 RX endpoint resources, in host mode these eps are allocated/freed dynamically for active usb request for connected devices. This can cater for most of typical host mode use cases.

What is the use case you are looking for and what kind of devices you want to connect in host mode.

Regards

Ravi B

0 RY9983 over 12 years ago in reply to Ravi B

Guru 10570 points

Bin-san, Ravi-san,
Sorry.
Although I asked them about USB usage of them, they could not disclose.
So, I tell them that AM335x has 15 Tx and 15 Rx endpoints and USB device counts depend on it.

Thank you very much for your support.
I would like to close this question.
Best regards, RY

0 Bin Liu over 12 years ago in reply to RY9983

TI__Guru**** 167581 points

Ok, as long as the use case does not use more than 15 Interrupt transfers simultaneously, the MUSB controller can support up to 126 devices in the topology defined in the USB 2.0 spec.

0 RY9983 over 12 years ago in reply to Bin Liu

Guru 10570 points

Bin-san,

Thank you so much for kindness.
But, I think USB spec specifies 127 devices.
I am refering below url.
http://en.wikipedia.org/wiki/Usb#System_design

Thank you again.

Best regards, RY

0 Bin Liu over 12 years ago in reply to RY9983

TI__Guru**** 167581 points

The root hub built in the MUSB driver is counted as one, so only 126 left.

0 RY9983 over 12 years ago in reply to Bin Liu

Guru 10570 points

Bin-san,
Great thanks!! I have been able to understand.
Best regards, RY

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How many devices can it be connected on AM335x USB I/F?