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LTC6813 Cell voltages Read - Command Sequence

Category: Software
Product Number: LTC6813 ADC

Hi 

I'm trying to Communicate LTC6813 using Arduino over the SPI Communication with (LTSketchbook) Examples over the SPI Communication.

Please share the Sequence which i need to follow to get the Cell Voltages of the connected Battery.

Suggest the options which i need to select for get the Cell volatages.

Note: Every power ON the Same Sequence is mandatory For Register Writings or one time is enough(EEPROM Savings are there?) 

  • Suggest the options which i need to select for get the Cell volatages.

    You should first send (3) Start Cell Voltage Conversions, this will send the ADCV Command to the device which will start the Cell voltage conversions in the device. Once this option is executed, you need to send (4) Read Cell Voltages to read the conversion results from the device. If you want continuous measurements then you can use the Loop Measurements option.

    Note: Every power ON the Same Sequence is mandatory For Register Writings or one time is enough(EEPROM Savings are there?) 


    No. The power cycle will reset the registers of the device. 

  • Hi Thanks for the Reply

    Please find the attachment for Commands which we are sending to ADC and getting responses from ADC.

    I hope we are able to communicate ADC over the SPI(based on Read Registers info available on attachment) but unable to get cell voltages.

    Please give the suggestions to debug to get the cell voltages.

    Also I'm attaching the Own developed PCB schematic please verify and give the feedback/suggestions to resolve this issue.PDF

    DOCX

  • From the captures you attached, I could notice that you are sending an All channels conversion request in Normal 7kHz Mode(MD[1:0]=10) thru ADCV. But on assuming you sent the PLADC Command immediately after the ADCV, the polling time it took(SDO line being pulled low by the device) seems very less considering it should have taken nearly 2.3ms to complete all channels conversion in Normal 7kHz Mode.
    I think you are not holding the CS low until the SDO is pulled back high by the device after PLADC to denote that the conversions are over.

    You can read more about using the polling commands in the Polling Methods section under Operations on Page no.56 of the datasheet.

  • Hi,

    Thanks for the Reply.

    I'll try as per your inputs,

    It means i need to hold the CS Pin Low until the SDO is Pulled Low to High by the ADC Device(Same condition applies for both after ADCV and PLADC Commands sent to ADC Device)

    Can you please check the Schematic once(available in my last message) and give the Confirmation/Feedback.

  • Can you please check the Schematic once(available in my last message) and give the Confirmation/Feedback.

    I don't see any issues in the Schematic that could have caused a problem in reading the correct cell voltages in your case.

  • Hi,

    I'll try as per your inputs,

    It means i need to hold the CS Pin Low until the SDO is Pulled Low to High by the ADC Device(Same condition applies for both after ADCV and PLADC Commands sent to ADC Device)-Correct?

  • It's either of those two.
    If you poll thru SDO directly after ADCV then you need not even send a PLADC command.
    Since ADC Conversions are already over when SDO is pulled high by the device after ADCV, you can directly read result registers after that.
    But in this way, you keep your controller busy checking the SDO line by waiting until conversions are over after ADCV, instead, you can send ADCV to the device and relieve control over SPI in your controller and when you need results, just to confirm whether conversions are over, you can provide PLADC and wait until SDO goes high and then read result registers.

  • Hi,

    Thanks for the Reply.

    As per your previous reply I maintained some delay for the ADC Measurements to finish then we are reading the Cell Voltages.
    PFA for the Captured State Machines for your reference.DOCX
  • Hi,

    Please find the attachment below for Cell Voltages Read State Machines.
    Observations:
    Case1: 
    1.Sent ADC Start Command(ADCV).
    2.Sent POLL ADC Converter Command(PLADC) to determine the status of the ADC Conversion.
    3.After Sending the PLADC Command SDO status changes from low to high after some delay (approx 1.59ms)
    4.The result of the Read cell voltage registers was 0xFF.
    Case2: 
    1.Sent ADC Start Command(ADCV).
    2. Wait for 5ms Delay
    3.After Sending the PLADC Command SDO status changes from low to high.
    4.The result of the Read  Cell voltages read were not the same as measured at the battery cells.
  • .The result of the Read cell voltage registers was 0xFF.

    What is the delay between the end of polling and reading back results from cell voltage registers?
    If it is greater than 2secs and there's no valid command being sent in that time period then the device will go to sleep resulting in all result registers getting reset to 0xFF.

    The result of the Read  Cell voltages read were not the same as measured at the battery cells.

    How much is the difference here?