TUSB8042A: Recognition issue

Shota Mago

Part Number: TUSB8042A

Tool/software:

Hi team,

My customer made prototype board using TUSB8042A, but it needs reset(toggling GRSTz) multiple times to be recognized by host CPU.

The number of reset cycle until the device is recognized by host is not consistent.

Once the device is recognized, even after reset again, the device is recognized properly again.

He confirmed his design follows power-up sequence requirement.

From console screen of the CPU, 80ff is shown as idPproduct whenever recognition fails. Meanwhile, 8240 is shown whenever the device is recognized properly.

What should he check so that the device is recognized successfully from the beginning?

Best regards,

Shota Mago

7 months ago

0 Brian Zhou 7 months ago

TI__Guru*** 148430 points

HI Shota:

Can I review your schematic first?

Best

Brian

0 Shota Mago 7 months ago in reply to Brian Zhou

TI__Expert 8250 points

Hi Brian,

I sent you the schematic which was provided from the customer, but the customer said when EEPROM is written properly, it seems that the device is recognized from beginning as expected.

If I receive additional question, I'll let you know.

Best regards,

Shota Mago

0 Brian Zhou 7 months ago in reply to Shota Mago

TI__Guru*** 148430 points

Hi Shota:

It seems pin 39 (SMBUSz) is pulldown, does customer really need SMBUS mode, if not just floating pin 39.

Best

Brian

0 Shota Mago 7 months ago in reply to Brian Zhou

TI__Expert 8250 points

Hi Brian,

Thanks for reviewing the schematic. Pulldown resistor for pin 39 is not populated. Only pad is prepared for just in case.

Best regards,

Shoat Mago

0 Brian Zhou 7 months ago in reply to Shota Mago

TI__Guru*** 148430 points

are there any other device share the same I2C bus?

Regards

Brian

0 Shota Mago 7 months ago in reply to Brian Zhou

TI__Expert 8250 points

Hi Brian,

There is no other device on same I2C bus.

The customer programmed EEPROM as default setting of TUSB8042A and it worked properly. So it seems that EEPROM must be used so that TUSB8042A is recognized properly.

The customer also noticed that on CPU console, it shows TUSB804"1" for TUSB8042A.

Best regards,

Shota Mago

0 Brian Zhou 7 months ago in reply to Shota Mago

TI__Guru*** 148430 points

Maybe PID/VID in EEPROM file is not correct?

it was correct before.

Best

Brian

0 Shota Mago 7 months ago in reply to Brian Zhou

TI__Expert 8250 points

Hi Brian,

Thanks for your suggestion.

The customer confirmed "8041" was disappeared on the console after he modified from 0x04 to 0x82.

Just to make sure, is TUSB8042A possible to use without external EEPROM?

To use TUSB8042A without EEPROM, is factory programming/special part number needed?

Best regards,

Shota Mago

+1 Brian Zhou 6 months ago in reply to Shota Mago

TI__Guru*** 148430 points

Shota Mago said:
Just to make sure, is TUSB8042A possible to use without external EEPROM?

yes, TUSB8042A will work in default mode without EEPROM.

This is correct.

Best

Brian

0 Shota Mago 6 months ago in reply to Brian Zhou

TI__Expert 8250 points

Hi Brian,

We found that recognition error issue was caused by connecting blank EEPROM. When he removed 0ohm resistor between EEPROM and TUSB8042A, the device starts up properly.

While, the customer would like to make sure behavior of OVERCURz/PWRCTL pin.

When OVERCURz is asserted to Low and overcurrent condition is removed(back go high state) after it, is PWRCTRL pin latched to Low state(disabling power switch)? Or does PWRCTRL pin just follow state of OVERCURz(no latch)?
When OVERCURz is asserted, does it affect(open) communication line such as DP/DM pins? Or does it only control PWRCTRL pin?

Best regards,

Shota Mago

+1 Brian Zhou 6 months ago in reply to Shota Mago

TI__Guru*** 148430 points

Shota Mago said:
When OVERCURz is asserted to Low and overcurrent condition is removed(back go high state) after it, is PWRCTRL pin latched to Low state(disabling power switch)? Or does PWRCTRL pin just follow state of OVERCURz(no latch)?

PWRCTRL will back to enable state once OVERCURRENT condition is cleared.OC

Shota Mago said:
When OVERCURz is asserted, does it affect(open) communication line such as DP/DM pins? Or does it only control PWRCTRL pin?

OVERCURz only affect PWRCTRL pin.

Best

Brian

Interface

Interface forum

TUSB8042A: Recognition issue