TUSB8041: Start-up Configuration Question

Ken W

Part Number: TUSB8041

We are using the TUSB8041 as a 2.0 Hub. My assumption from reading the data sheet was that with the configuration shown below, that the hub would boot up using the strapped pins sampled at reset deassertion and then we could access the part via the SMBUS pins. What we see is that when we power up (GRSTz meets the power on timing requirements), the hub does not come up and u-boot does not find the device. If we remove R227 and R228 (the SMBUS), the part powers up fine. We can install a USB stick down stream and u-boot finds the hub as well as the down stream memory stick. The SMBUS is at a normal idle state with SCL/SDA pulled up to 3.3V. Am I reading the data sheet incorrectly?

over 6 years ago

0 Ken W over 6 years ago

Prodigy 40 points

It appears that the schematic did not show up in the initial post. I'm giving it a second go.

0 JMMN over 6 years ago in reply to Ken W

TI__Guru 60865 points

Hi Ken,

Your schematic did not show up yet, however, the TUSB8041 will not connect to the USB host if SMBUSz is asserted until the CFGACTIVE bit is cleared by writing a 1 to bit 0 of register 0xF8h.

Regards,

JMMN

0 JMMN over 6 years ago in reply to JMMN

TI__Guru 60865 points

Hi Ken,

I received your schematic through an internal email, but the SMBUSz setting is still the most probable cause of the issue. Was the issue resolved?

Thanks,
JMMN

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TUSB8041: Start-up Configuration Question