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BQ27541 I2C OK, no HDQ

mtucker
Prodigy 130 points
Other Parts Discussed in Thread: BQ27541, BQ27010

Part: BQ27541

Interface to Windows computer: EV2300 and TI bq Evaluation Software

Part environment: bq27541 TI circuit module (demo board) and our own board (both work fine I2C, but not HDQ)

Both the demo board and our board have the same problem.  I can read current and voltage (very accurate) via I2C, but when I tell the part to go to HDQ mode the part seems to stop working.   Here is the scenario.  Using I2C, I read the voltage and current with the BQ Evaluation software.  All is fine.  Then I use the BQ Eval software to tell the IC to go into HDQ mode.  HDQ is what we need in our product.  I get warnings saying that I can't go back to I2C once I switch to HDQ.  I have it proceed.  I then turn off power to the board/BQ27541.  I move the cable to the EV2300 HDQ connector and do the same on the demo board.    I quit the BQ Eval software and then restart it.  I apply power to the circuit.  Nothing.  Monitoring the HDQ line shows me there is a pull up R in the EV2300.  The HDQ line sits near 3.3V.   I get an error message from the BQ Eval software about not connecting and the HDQ line does not pull low (not even once).  It doesn't seem like it is trying to talk.

I have not done/made any configuration files (DFI,  .CHEM, .ENCR, .EZY) since I am only using the voltage and current reading capability of the BQ27541.  I do not need impedance tracking or any other smart features of the IC. .  Since my votlage/current readings work great with I2C, I wouldn't think I would need to program those files to get the same results using HDQ.

Thanks,

Matt

 

  • 0
    TI__Intellectual 940 points

    Matt,

    It's clear that the issue is NOT with the part, since you say that the HDQ line never pulses low.  The HDQ line from the EV2300 should output the HDQ address, even with nothing connected to the HDQ line.  I expect your issue is that you are still using the same evaluation software after converting the part to HDQ.  The evaluation software for HDQ is different.  When you start the evaluation software, make sure you choose the HDQ version that matches the firmware version in the bq27541.

    Bill

  • 0 in reply to Bill J10799
    Prodigy 130 points

    Bill,

    Thanks for the reply.  Right.  When the BQ eval software starts, there are three options, "all", one with HDQ in the name, and one with HDQ not in the name.  I chose the one with HDQ in the name..... and then eventually the other two options since HDQ wasn't working with the HDQ option.

    Matt

  • 0 in reply to mtucker
    TI__Intellectual 940 points

    Matt,

    I assume that you have done a power reset of the bq27541 after sending the command to convert it to HDQ.  I also assume you have moved the communication connector to the HDQ position on the EVM as well as the EV2300.  If the HDQ line is constantly high and you are getting no pulses at all when scoping the HDQ line and you have polling enabled with the evaluation software, then I would question whether the EV2300 or evaluation software installation has a problem.  You might contact your local TI  AFA and ask him whether he has a different EV2300 that you could try.  You could even download evaluation software for a different gauge, such as the bq27010 and scope the HDQ line after selecting EV2300 and HDQ options from the pull down menu.  Actually, the bq27010 software should be able to read voltage from the bq27541, as the address and units are the same for both parts.  This would help confirm whether your issue it is a problem with your evaluation software or EV2300 installation.

    Once you have established communication, you may want to make sure that your pullup resistor is small enough.  The rise time needs to be less than 1usec for proper communications and depending on the capacitance on your HDQ line, even the pullup that is in the EV2300 may not be small enough.  You can add an externa parallel pullup resistor of about 10k from the HDQ pin to the VCC pin of the EV2300 connector to easily.do this.  However, this isn't going to fix you issue of not seeing any pulses at all.

    Bill 

  • 0 in reply to Bill J10799
    Prodigy 130 points

    Bill J said:
    I assume that you have done a power reset of the bq27541 after sending the command to convert it to HDQ.  I also assume you have moved the communication connector to the HDQ position on the EVM as well as the EV2300. ..................Bill

    No need to assume.
    MTUCKER said:
    I then turn off power to the board/BQ27541.  I move the cable to the EV2300 HDQ connector and do the same on the demo board.    I quit the BQ Eval software and then restart it.  I apply power to the circuit.

    Neither the TI eval board nor our board has a pull up R on it.   I am relying on the EV2300 pull-up R for now.  Once we get communication going, I will keep that in mind (adding another pull-up). 

    I talked to the Systems person working on the project with me.  He said he also noticed the HDQ line not doing anything when the BQ Eval software gives the ACK error (saying it isn't finding a BQ27541), but he said that if he ignored that and then tells the BQ Eval software (PC) to try to read voltage that he DID see the HDQ line go low.  So it does sound like the EV2300 interface is capable of toggling the HDQ line.  I'll look at the HDQ line more and confirm what he saw.

    Thanks,

    Matt

     

     

     

     

     

  • 0 in reply to mtucker
    Prodigy 130 points

    Bill,

    You hit it with the pull-up R advice. 

    I did not see HDQ data on the startup of the program before I got the ACK warning, but if I hit OK and let the program start I saw data when it was polling.  I then tried the  bq27010 software as you suggested.  I could tell I had partial communication because three or so boxes had data in them and occasionally I would see "communication OK" at the bottom left corner.  It worked enough for me to see that the BQ27541 was trying to talk back.  The BQ27541 pulses were only going up to about 2V.   I tacked a 10K ohm pull-up R on our board and BAM!.... she was talking. 

    It is interesting that neither our board nor the TI eval board worked.  It seems like the TI eval board needs the additional pull up R to work properly.

     

    Thanks,

    Matt