TS3USB221: Using TS3USB221 to switch between (2) hosts to downstream device

Gary Beck

Part Number: TS3USB221

We are using a TS3USB221 to switch between (2) hosts and a downstream device. Host #1 is connected to the 1D+/- pins. Host #2 is connected to the 2D+/- pins. The downstream device is connected to the D+/- pins. Upon power application the OE input pin is pulled low and the S input pin is pulled high connecting Host #2 to the downstream device. To perform a switch over to Host #1 software clears the S input pin leaving the OE input pin low. Each host computer is running Windows 10. Switching from Host #2 to Host #1 rarely works however switching back from Host #1 to Host #2 always works. Does anyone see an issue with this dessign approach?

over 2 years ago

0 Stanton Weaver over 2 years ago

TI__Intellectual 2850 points

Hi Gary,

Thank you for your question. Can you please provide a block diagram?

Best,

SLW

0 Gary Beck over 2 years ago

Prodigy 10 points

See below for the block diagram of the implementation. Currently the OE pin is kept low during a switch over event as initiated by the micro-controller.

0 Gary Beck over 2 years ago in reply to Gary Beck

Prodigy 10 points

Do you have any feedback to the implementation described above?

0 Stanton Weaver over 2 years ago in reply to Gary Beck

TI__Intellectual 2850 points

Hi Gary,

Sorry for the delayed response. We had a holiday weekend.

What is the vbus status when you switch from host 1 to host 2?

Best,

Stanton

0 Gary Beck over 2 years ago in reply to Stanton Weaver

Prodigy 10 points

Hope your holiday was relaxing.

VBUS remains constantly applied during a switch over.

0 Stanton Weaver over 2 years ago in reply to Gary Beck

TI__Intellectual 2850 points

Hi Gary,

Thank you! It was :)

Once you switch host, you need to switch Vbus as well. VBUS cannot remain constantly applied. Please let me know if this fixes the problem.

Best,

Stanton

0 Gary Beck over 2 years ago in reply to Stanton Weaver

Prodigy 10 points

Stanton,

We will have to modify the design to be able to switch VBUS. The downstream device includes a USB hub. After reviewing the datasheet it makes sense that VBUS needs to be disabled then re-enabled to ensure the connected device signals a connect event.

0 Stanton Weaver over 2 years ago in reply to Gary Beck

TI__Intellectual 2850 points

Gary,

Please keep me updated if you have further questions once you modify the design.

Best,

Stanton

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TS3USB221: Using TS3USB221 to switch between (2) hosts to downstream device