TUSB2046B: hub enters SUSPND mode

ROHIT GARG

Part Number: TUSB2046B

Hi,

I have been testing the TUSB2046 with a custom PCB. I am using only 2 downstream devices.

When I power on and connect the hub to my Windows laptop, I only get 'Generic USB hub' in the USB enumeration. I dont get any downstream device enumeration. When I probed the SUSPND pin, it was pulled high.

I have attached my schematic(I have a small stub on the upstream USB for an optional 2nd USB connector).

Please help.TUSB2046_test.pdf

Thanks,

Rohit

over 6 years ago

0 JMMN over 6 years ago

TI__Guru 60870 points

Please remove the 1.5K series resistors, those should not be installed. Can you check VBUS and DP/DM levels on the downteam ports?

Regards,
JMMN

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

I'm sorry, those are 22 ohms, forgot to change that on schematic.

0 JMMN over 6 years ago in reply to ROHIT GARG

TI__Guru 60870 points

Ok, check the line states and VBUS on the downstream ports.

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

So the downstream ports are self-powered through a supply. I'll check DP/DM levels.

0 ROHIT GARG over 6 years ago in reply to ROHIT GARG

Prodigy 120 points

I don't see any activity on downstream DP/DM lines.
But before that, what I notice is hub goes into SUSPND mode(and clock stops) few seconds after it's powered, while it's connected to the PC upstream.

0 JMMN over 6 years ago in reply to ROHIT GARG

TI__Guru 60870 points

A hub will be suspended by the host if it doesn't see any downstream devices connected. When the hub enters supsend, you should see DP or DM be pulled high on the populated downstream ports. Does this occur?

Does providing a manual reset tot he TUSB2046B result in the downstream devices connecting?

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

I have been playing with the RC network on the RESET line.
Initially, I used 47k, 0.1uF as found in the schematic here: www.ti.com/.../TIDM-3LC-METER-CONV

Then I changed to 15k, 1uF as found here: e2e.ti.com/.../476641
Now, I don't see the hub going to into SUSPND, and clock remains running. But now the PC doesn't recognize the USB device(hub). I get an 'unknown USB device' message now.

Any idea about the correct RC circuit?

Even with a manual reset in both cases I couldn't see downstream devices connecting.

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

DP/DM are not pulled high when hub enters suspend.
What can be the issue?

0 JMMN over 6 years ago in reply to ROHIT GARG

TI__Guru 60870 points

What's the voltage on VCC on the downstream ports? Wither DP or DM should be pulled high if the downstream ports are connected and powered.

0 JMMN over 6 years ago in reply to JMMN

TI__Guru 60870 points

VBUS on USB cables is typically 5V. A Full Speed or High Speed USB device should have DP high, a Low Speed USB device should have DM high.

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

My downstream devices are self powered. But still, I tried supplying 5V to downstream devices via VBUS.

The DP line does go high. The computer cannot recognize any downstream device.

Also, could you clarify the RC circuit on RESET pin?

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

UPDATE: now my hub does not go into Suspend mode. I realized my PC was forcing it into suspend as the Power management option was enabled.

So the hub enumerates as a 'generic USB device' on the PC.

However, downstream devices are not detected/enumerated on PC. I have externally supplied 5V on the downstream VBUS too.

What might be happening?

0 JMMN over 6 years ago in reply to ROHIT GARG

TI__Guru 60870 points

What is occurring on the downstream DP/DM lines? Can you confirm that the overcurrent inputs are high?

Can you provide a screenshot of the device manager window?

0 ROHIT GARG over 6 years ago in reply to JMMN

Prodigy 120 points

The downstream DP is pulled up to 3.3V. DM is low. Overcurrent inputs are high.

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TUSB2046B: hub enters SUSPND mode