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BQ79656EVM-021: BQ79656EVM-021

Vaishali Balakrishna Shetty
Prodigy 115 points
Part Number: BQ79656EVM-021

Hi,

I am trying to wakeup bq79656 from sleep mode. 

I have configured the CONTROL1 register to set the SEND_SLPTOACT bit to 1, but the device does not wake up from sleep mode.

  • 0
    TI__Expert 6710 points

    Vaishali,

    Setting the bit CONTROL1[SEND_SLPTOACT] makes the device send SleepToActive tones up the daisy chain to other stack devices and will not change the functional mode of the device the bit is set in. Do note that in SLEEP mode the device cannot read normal UART and so sending a write command to the device in SLEEP mode will do nothing. You must send a SleepToActive ping, which is similar to the wake ping used to turn on the device but is only 275 us long. You can read more about this in section 9.4 of the datasheet.

    Regards,

    Ben

  • 0 in reply to Benjamin Luty
    Prodigy 115 points

    Based on the datasheet, I understand that sending a WAKE ping to the BQ79656 will wake it up from SLEEP mode. After sending the WAKE ping, is it necessary to perform a digital reset of the device? Are there any specific commands or procedures that need to be followed.

    Thank you 

  • 0 in reply to Vaishali Balakrishna Shetty
    TI__Expert 6710 points

    Vaishali, 

    Sending a WAKE ping to a device in SLEEP mode will bring it into ACTIVE mode. Receiving a WAKE ping also forces the device to perform a digital reset, changing all registers back to their default setting, potentially forcing you to redo auto-addressing, starting the ADCs, and other configurations. 

    You can also send a SLEEPtoACTIVE ping, which is different to the WAKE ping. This will bring the device from SLEEP mode to ACTIVE mode without resetting all of the registers.  

    Regards,

    Ben

  • 0 in reply to Benjamin Luty
    Prodigy 115 points

    Can you provide details for sending the SLEEPtoACTIVE ping to the BQ79656? Where can I find this information in the datasheet

    Thank you

  • +1 in reply to Vaishali Balakrishna Shetty
    TI__Expert 6710 points

    Vaishali,

    As mentioned previously, you can find this information in section 9.4 of the datasheet. Pings are specifically in section 9.4.3.1 and are all high-low-high signals to the RX pin of the device. The SLEEPtoACTIVE ping, specifically, is between 250 and 300 us long. You can find the timing information in section 8.6 under "PING SIGNAL TIMING".

    Regards,

    Ben