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Original question:

BQ76920EVM: Device won't boot/work with bqStudio

BQ76920EVM: Boot button not working

Justin Ochoa
Prodigy 130 points
Part Number: BQ76920EVM
Other Parts Discussed in Thread: BQ78350, BQSTUDIO, , EV2400, BQ76920, BQ78350-R1

Hi, I am having trouble with the boot button on one of the bq76920EVM devices that we ordered. The dashboard shows the EV2400 is connected but the bq78350 is grayed out on bqStudio (using SMB). The bottom status bar also shows that there is "no acknowledgement from device". I have collected some voltage measurements as shown below.

VC1: 3.769V
VC2: 7.54V
VC3: 11.31V
VC4: 15.08V
VC5: 18.85V
BAT: 18.28V
CAP1: 3.292V
BAT+: 18.85V
REGOUT: 2.523V

I have also tried testing the bq76920EVM board using the evaluation software but still having problems with the boot button. Are there any troubleshooting steps that you suggest we should try to fix this board.

Thanks,

Justin

  • 0
    TI__Guru 54715 points

    Hi Justin,

    The boot button has worked since REGOUT is 2.5V.  If you remove power and re-apply, check REGOUT, it should be 0.  Press the boot button and it should go to 2.5.

    You will need shunts for the pull ups when using the gauge, as well as the 4 shunts to connect the REGOUT, ALERT and I2C to the gauge.  Be sure you measure 2.5V at the GG_PWR test point also.  Use the SMB connectors.

    If not using the gauge, remove the 4 shunts to connecting the gauge.  Remove the pull up shunts if using the EV2400 since it has internal pull ups to 3.3V.  Use the I2C connectors.

    See the EVM user guide for operating information.

  • 0 in reply to WM5295
    Prodigy 130 points

    I removed and reapplied power as you mentioned and saw the value for REGOUT go from 0 to 2.5V after pressing the boot button. GG_PWR is also showing 2.5V. I am mainly using the gauging functionality of this board with bqStudio.

    When selecting the "Register" tab to view the values, I am seeing an error that says "No acknowledgement from device".

    When selecting the "Data Memory" tab, I am seeing an error that says "Operation failed because initial read of all data flash failed".

    When selecting the "Firmware" tab, I am seeing an error that says "Program Srec: No acknowledgement from device".

    When selecting the "Errors" tab, I am seeing errors that say "Message: No acknowledgement from device;    View: Register;    Operation: Refresh".

    Are there any additional steps that you suggest I can try?

    - Justin

  • 0 in reply to Justin Ochoa
    TI__Guru 54715 points

    Hi Justin,

    It sounds like the gauge won't talk to you.

    With the gauge powered and the board booted, look at the I2C with a scope.  If the lines are low the pull ups may be missing.  If the lines pulse every 250 ms, perhaps in some groups, the gauge it is talking normally.  If the lines are continuously toggling the gauge can't find the BQ76920 and will ignore SMBus trying to talk to the BQ76920.  If I2C is high it would seem the gauge is no talking.  Look for damaged shunts, traces, or contamination.  You mention GG_PWR is ok so that shunt must be OK.

    If the I2C looks normal with bursts of traffic, check the SMBus lines with a scope.  If they are not high (pull ups come from the EV2400) check for a bad cable or contamination on the board shorting the lines low. When you try a register read you should see a burst of traffic.  If you have the lines pulled high and a burst of traffic but no response, check that the shunt is installed on J13 pins 2-3 for the normal SMBus address.

  • 0 in reply to WM5295
    Prodigy 130 points

    Sorry for the delay, I just got access to an oscilloscope today and was able to test measurements based on your troubleshooting steps.

    On one of the working EVMs, I was able to see the pulses (every 250 ms) on the I2C lines that you mentioned. I was also able to see the burst of traffic on the SMB lines of the working EVM when collecting data on bqStudio.

    On the non-working EVM, I only saw a constant signal of 2.5V on the I2C lines. I have attached a screenshot with the output from the I2C lines. I have checked the board and there doesn't appear to be any damaged shunts or contamination. Unfortunately, I was unable to test the SMB lines since the board is not communicating with bqStudio.

    Is it possible that this can be a firmware issue? Based on the Gauge Quick Start section of the User's Guide, I downloaded and installed the bq78350R1 Firmware Bundle (ver1.04) in the "sluc594a.zip" file, but there was an error when installing. I don't recall what the exact error was and now I can't reinstall the firmware because of the "No acknowledgement from device" error message. Are there any steps to reinstall or rollback the firmware to factory settings?

  • 0 in reply to Justin Ochoa
    TI__Guru 54715 points

    Hi Justin,

    Sounds like the gauge has corrupt firmware and is in ROM mode, it will not talk on I2C.  It will error on many normal commands. Usually it can be reprogrammed.  Be sure the firmware installer ran correctly so that the firmware file is complete.  A little more commentary than is in the EVM user guide http://www.ti.com/lit/ug/slvu924d/slvu924d.pdf :

    • On the board, connect the gauge to the monitor/AFE with the 4 shunts, and install the pull up shunts. 
    • Connect the SMB connector to the interface. 
    • Power the board and boot. Be sure you have a stable supply and connection for operation but especially for programming.
    • Confirm you have 2.5V on GG_PWR.
    • Start BQStudio and select the BQ78350-R1.  
    • Go to the Advanced Comm SMB tab, Read Word 0D.  You should be able to scope the SMB lines for this transaction and read repeatedly as needed.  

    If it responds you should be able to program the firmware with the Firmware tab.  If it gives some response other than the 303 shown below, you can send MAC command 0F00 with the Write Word tool, see the technical reference manual section 17.2.58. The 0F00 command only works from normal mode, in ROM mode with the 303 response at 0D it will show an error. If you have entered ROM mode manually, you may get a message in the firmware tab that it is already in ROM mode, acknowledge if necessary.

    If the gauge won't ack the SMB read of 0x0D, and GG_PWR is 2.5V, check for contamination, shorts, or opens.  If all is good the BQ78350-R1 is probably dead, I don't know what would have happened to it, but if it has power, connections and won't talk, it is dead.