BQ78350-R1: bqStudio is not showing cell voltages

Hello Mike

Did you follow making right connection for J14 ?

Hi Jessica,

Thanks for the suggestion.  I forgot to mention the state of the jumpers in my original post, but can confirm that all 4 jumpers are enabled on J14.

I've attached a photo of the board showing the removed diodes, the shorted cells, and the jumpers in position.

I don't know if this is relevant, but in the documentation for the EVM on p19 it mentions the default configuration of the firmware for the bq78350 is for 3 cells.  It goes on to say that 'The device must be configured for operation with other cell counts, this includes basic operation of the EVM.'  I haven't carried out any 'cell count' configuration - despite looking through the documentation I can't find any reference on how to do this.  The only related(?) step I've done is to set the Ext Average Cell Voltage to 3353mV.  This step was successful but it didn't result in the individual cell voltages being displayed.

I've just found out how to configure the bq78350 for 8 cells.  For anyone interested, the configuration is done via the Data Memory tab of the bqStudio.  Under Settings, select the AFE Cell Map and then select the cells you have connected.  In my case, having an 8 cell battery,  the battery cells from 1-8 are connected to input cell connectors 1, 2, 3, 5, 6, 7, 8, 10 (as per the bq76930 documentation).  This results in the map settings value of 0x02f7.  Attached is a picture of the screen and my new settings.

However, this has NOT resolved my original issue, namely the cell voltages are not being displayed when I run the EVM in the gauge mode.

Hi Mike,

Can you send a screen capture of the Register screen now that the AFE Cell Map is configured? It would be good to see if there are any faults present that are preventing the voltage readings. It looks like the AFE_OVRD bit was set in the previous screen capture. Also, you may have already done this, but after setting the AFE Cell Map, it is necessary to execute a Reset command (click Reset button on right hand panel) and then click the Refresh button on the Registers screen to update the cell voltage readings.

Best regards,
Matt

Hi Matt

I'm attaching a few screen shots of the registers because they keep changing.

From what I can tell, this is what they are doing.

Safety Alert A+B (High) is toggling between 0x0000 and 0x10000.

Safety Status A+B (High) is toggling between 0x12f1, 0x02f1 0x02a1, and 0x0251.

I tried the RESET button and it returned a result value of N/A - not sure if this is what you expected.  Regardless, this, and the subsequent Refresh did not fix the issue.

Hi Mike,

It looks like you are using the 'LT_RESET' command. This command resets the values stored in the Lifetime data. If you scroll down the list of Commands, there should be a different 'RESET' button. This one should reset the device so that the new AFE cell map settings take effect.

Best regards,
Matt

Hi Matt,

You're correct in that I did use the 'LT_RESET' button, but I then found the 'RESET' button a bit later.  

I've tried the sequence you suggested again, but still having the same issue.  

I've attached screenshots showing the steps I took - perhaps one of these will help show what is going wrong.

I might be mistaken, but it seemed that the 'RESET' only took effect after I had pressed 'UNSEAL' - is the chip normally in a sealed state?

Once 'RESET' had occurred, the AFE Cell map was empty.

I then set the cells as shown in the following screen shot.

The new cell settings were written to DF using the 'Write_All' button, and I then checked that they had been successfully stored by reloading all settings.

I then calibrated the gauge, setting the average cell voltage to 3.328V.

In the Registers window, I pressed Refresh (and also had rebooted the board previously), but again, no cell voltages displayed.

Hi Mike,

It looks like there must be a communication problem between the BQ78350-R1 and the BQ76930.

Can you try to install the jumpers on the SCL and SDA pull-up headers? - it looks like they are not installed in the picture.

Another possibility that could cause the 0mV readings is an XREADY fault from the BQ76930. XREADY indicates that something is not powered correctly on the BQ76930. You can measure the CAP1, CAP2, REGOUT, VC5X, and VC10 test point to see if the expected voltages are present.

One other unlikely possibility is that the I2C address of the BQ76930 is not 0x08. From your screen capture of the BQ769x0 GUI, it appears to be correct with this value. If the device on the EVM has been changed and the address is different, the BQ78350-R1 will not be able to communicate with the BQ76930. Like I said, I think this is unlikely.

Matt