TUSB2077 enumeration without Host PC

Phillip Crosby

Other Parts Discussed in Thread: TUSB2077A

Hello,
I am designing a USB hub around the TUSB2077APT and I have questions regarding the enumeration of downstream devices.

For 90% of the time the hub is used it will not be connected to a host (upstream) computer, and the downstream devices will be charging on the hub. The TUSB2077APT is set up for Self-Powered mode without the use of the _PWRONx ports (or the use the _OVRCURx ports).

The question I have is, if there is no host (upstream) computer, will the TUSB2077APT enumerate to the devices attached downstream? The reason for this is the downstream devices are intelligent enough to notice enumeration to an upstream device (host or hub) and choose a higher charging current rate. This is preffered so the downstream devices take a shorter time to fully charge.

Kind Regards,

Phillip

over 10 years ago

0 Elias Villegas M. over 10 years ago

TI__Guru* 76130 points

Moving to the correct forum.

0 Joel Jimenez0 over 10 years ago

TI__Mastermind 18655 points

Hello Phillip,

No, per USB spec, a HUB should be fully under the control of an USB host system.
The USB host controls the port power of a USB hub using power commands that are sent during system power on / off, reboot, sleep and resume as needed.
Please, provide more details on your application, then I will be able to provide another solution.

Regards.

0 Phillip Crosby over 10 years ago in reply to Joel Jimenez0

Prodigy 55 points

To clarify, the TUSB2077 will not recognize downstream devices without an upstream host while being powered by a secondary source (Self-Powered not bus-powered)?

0 Joel Jimenez0 over 10 years ago in reply to Phillip Crosby

TI__Mastermind 18655 points

No, it will not. The USB host controls the downstream-port power of a USB hub using the SET PORT FEATURE (PORT POWER) and CLEAR PORT FEATURE (PORT POWER) commands, these commands cause the TUSB2077A to assert or dessert the PWRONz outputs.

Regards

0 Phillip Crosby over 10 years ago in reply to Joel Jimenez0

Prodigy 55 points

Joel,
I am not using the PWRONx outputs nor the OVRCURx outputs. None of the power circuitry for down stream ports use these ports.

Interface

Interface forum

TUSB2077 enumeration without Host PC