• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 62 subscribers
  • Views 302 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ76942EVM: No communication to PC via USB

AhtoM
Prodigy 40 points
Part Number: BQ76942EVM
Other Parts Discussed in Thread: BQSTUDIO, , BQ76942

Greetings,

Out of ideas here.
Our BQ76942EVM board has been working previously but now after sitting on a table for about a month (until I got time to go at it again) I cannot seem to connect to it via BQStudio anymore, as if there's no communication via USB.
Usually I press WAKE button and I could connect through BQStudio. Now BQStudio won't detect the chip after pressing WAKE.

I'm using an actual 6-series-cell battery (26V) to connect to the EVM in such configuration on the EVM:


Measured some relevant signals:

TP2 BAT - 22.9V (correct for current SOC level).
TP3 CP1 - 33.7V (charge pump seems to work)
TP10 REG18 - 1.8V (REG 1.8V is functional once balancing cable is connected).

I was suspecting that perhaps chip is stuck in somekind of SLEEP mode.
I've exhausted some of the SLEEP mode topics here on the forum:
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1273424/faq-bq76952-how-does-shutdown-mode-work?tisearch=e2e-sitesearch&keymatch=bq76952%2520faq
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1273427/faq-bq76952-what-is-the-soft-shutdown-state
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1181117/faq-bq76952-how-do-i-reset-the-bq769x2-device

One post refers to doing a partial reset by pressing RESET button. So I measured the relevant signals:

TP11 TS2 - 0.05V (floating)  0V when WAKE button held down.
-  Perhaps multimeter may pull it low when trying to measure this?
TP7 REG1 - 0.618V
- REG1 has no significant output voltage to pull RST_SHUT up to !? Thus reset may not work at all...
BREG and REGIN are 0V

Are these levels expected ?
As of context, I have no other external circuitry attached to REG1 or TS2 pin.
I have also tried replacing the BQ76942 chip on the EVM, no change.

Connecting EVM via PSU and using the on-board cell simulation, only enables the FUSE LED and still no communication.

How would You suggest to go further to debug this ? As it worked some time before...

  • 0
    Prodigy 40 points

    I would also add that for the USB connection, the USB chip M430F5529 seems to work. LEDs are all on, (meaning 5V is coming in and 3.3V is regulated). I suspect that there's no connection to the BQ chip itself...

  • 0 in reply to AhtoM
    TI__Mastermind 25980 points

    Hi Ahto,

    If the device is unable to communicate, but REG18 is high, the device is likely in soft-shutdown. You may want to check the voltage at the LD pin to see if it is still high. You may also check that the shunts for the I2C line are installed properly.

    If the FUSE pin is being asserted, then that indicates a secondary protection has triggered. You may try looking through Section 5.3 of the TRM to see if any secondary protection has been triggered.

    Regards,

    Max Verboncoeur

  • +1 in reply to Max Verboncoeur
    Prodigy 40 points

    Thank you for your reply.

    Well, the LD pin is always 'low' since I have not hooked up any charger, right ? (BQ is also not outputting any battery voltage to PACK).
    Thus I don't see how LD pin can go high when hooking up the battery only, with no load.

    For my setup currently, I am only hooking up the battery with balancing cable and a USB cable to PC.
    Shunts are present on J11, J14 for Pull-Ups.

    I tried different scenarios and

    When I removed the shunts on J11 and J14 - sure enough, BQStudio started to communicate via USB !

    Truthully, 'no shunts' are kind of shown in the EVM user manual, when not using external MCU, but it's not clearly mentioned that with on-board USB connection only, these must be removed...

    // removed follow-up question, which was not so related anymore.

  • +1 in reply to AhtoM
    TI__Mastermind 25980 points

    Hi Ahto,

    If the issue was the placement of the shunts and you're able to communicate now, then soft-shutdown was not the problem. It sounds like everything is solved now.

    Regards,

    Max Verboncoeur