AM3358: USB VBUS connection

weiji jiang

Expert 2040 points

Part Number: AM3358
Other Parts Discussed in Thread: AMIC110

Hi TI Folks,

Good day to you.

In my customer's design, the AM3358's USB1 works as host, it connects to a USB modem which has separated 3.3V power supply, there is no power supply connect to AM3358's USB1_VBUS. From datasheet, it shows the USB1_VBUS is the Supply voltage for USB VBUS comparator input. Do the USB1_VBUS must connect to power supplier? If yes, Is there any idea to solve this problem by S/W without modify the circuit connection..

Best regards

Jiang WeiJi

over 8 years ago

0 Biser Gatchev-XID over 8 years ago

TI__Guru**** 393215 points

Hi,

Please follow this checklist:

A simple transistor circuit can be used instead of a VBUS switch:

0 weiji jiang over 8 years ago in reply to Biser Gatchev-XID

Expert 2040 points

Hi Biser,
Good day to you.
Thanks for your sharing. Do the VUSB_VBUS1 above be the same to AM3358's USB1_VBUS?
Please correct me if I am wrong: Simply to say, the AM3358's USB1_VBUS pin must be connected to V5_0D power supply ether through mosfet or load switch.

best regards
Jiang WeiJi

0 Biser Gatchev-XID over 8 years ago in reply to weiji jiang

TI__Guru**** 393215 points

Yes, this is correct.

0 weiji jiang over 8 years ago in reply to Biser Gatchev-XID

Expert 2040 points

Hi Biser,

In the design, the USB device is a modem which mounted at the same PCBA with AM3358 together, and it was permanently connected to AM3358's USB1 directly.

Looks like the USB can be configured to a host by software, which mentioned in page No.2504 of "AM335x and AMIC110 Sitara™ Processors Technical Reference Manual" (16.2.7 USB Controller Host and Peripheral Modes Operation).

Please share the details, how to directly configure the USB as a host in AM3358's USB1.

best regards

Jiang WeiJi

0 Biser Gatchev-XID over 8 years ago in reply to weiji jiang

TI__Guru**** 393215 points

What software are you using? Which version?

0 weiji jiang over 8 years ago in reply to Biser Gatchev-XID

Expert 2040 points

Hi Biser,

Below mentioned Uboot and kernel version is used:
U-Boot:
From git://git.ti.com/ti-u-boot/ti-u-boot.git Base on 2017/05/02 version

Kernel:
From git://github.com/beagleboard/linux.git Base on 2017/05/03 version

best regards
Jiang WeiJi

0 Bin Liu over 8 years ago in reply to weiji jiang

TI__Guru**** 168141 points

No matter what mode the musb controller will work on, the USB1_VBUS pin has to be connected, there is no software workaround for it. For host-only mode, you can connect USB1_VBUS to 5V power rail directly, and set dr_mode="host" in your board dts file.

Here are a couple things to pay attention please.

- Only the TI processor SDK is supported by TI, we are unable to support any issue you would have with a community kernel.

- I am not familiar with the modem device you use, but it sounds like the modem on PCB doesn't have VBUS input. According to the USB protocol defined in the USB Specs, an USB device should pull up DP/DM after sensed VBUS. So you have to ensure the modem brings up its DP/DM pullup at the right timing; otherwise, the host will fail to enumerate it.

0 weiji jiang over 8 years ago in reply to Bin Liu

Expert 2040 points

Hi Bin Liu,

Good day to you.

Thanks for your reply.

Best regards

Jiang WeiJi

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AM3358: USB VBUS connection