TUSB8042A: It's not working with SMBUS.

Hi Hiroshi 

    in SMBUS mode, SMBUSz should be low and SCL/SDA should be pulled up to 3.3v?

   does SMBUS address correct?

Best

Brian

Hi Brian,

Thank you for your comment.

There is no problem in confirming the points raised.

Even if the sub address is incorrect, wouldn't the write data from the master still be output?

As for future confirmation, what will be the behavior if it is not possible to ensure a delay of 3ms or more for VDD and GRSTz with "Power-Up Timing Requirements"?

Best regards, 

Hiroshi Yamada

Hi Brian,

I checked the GRSTz waveform.

I believe 3 ms is secured, but just to be sure I changed the external capacitor from 1uF to 2uF, but the phenomenon did not change.

Will it be a problem if VDD rises slower than VDD33?

Will it be a problem if GRSTz is released more than 3ms later using an RC circuit after VDD has stabilized at 1.1V and VDD33 at 3.3V?

Do I need to make changes to the active reset circuit?

Best regards,

Hiroshi Yamada

Hello,

Today is a US National Holiday, as a result, responses may be delayed. Thank you for understanding!

Regards,

Jack

Hi Hiroshi : 

    Please set SMBUSz pin floating ( I2C mode) to make sure hub works in normal I2C mode.

  If I2C was not work, check 1.1v/3.3v/GRSt wavform to make sure pwoer on sequence is correct.

   If I2C mode works, then pulldown SMBUS pin and pullup on SCL/SDA  to make hub into SMBUS mode.

  in SMBUS mode, make sure address is correct based on xyz setting.

   Here is the debug procedure if hub does not not work.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1343233/faq-tusb8041a-debug-procedure-if-ti-tusb80xx-or-tusb40xx-hub-can-not-be-detected-by-usb-host?tisearch=e2e-sitesearch&keymatch=TUSB8042A#

Regards

Brian