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BQ79600EVM: Sending Wake Command to Bq79616EVM Not Working - UART

Braden Sunwold
Prodigy 150 points
Part Number: BQ79600EVM
Other Parts Discussed in Thread: LAUNCHXL-F28379D, BQ79616,

Hello, 

I am trying to complete the initialization of the Bq79600EVM with one Bq79616EVM. When I send the wake pulse to the Bq79600, I see the D2 LED turn green and the D3 LED turn red. After this, I try to send the wake up command CONTROL1[SEND_WAKE]=1 to the Bq79600 in order to wake up the Bq79616 but no lights turn on on the Bq79616EVM and I don't see any activity on the daisy chain when probing it. I am using the LAUNCHXL-F28379D dev kit as the host microcontroller.

At first I was initially setting the UART baud rate to 250Kb/s and did confirm that I was sending the correct data to the CONTROL1 reg, "90 00 03 09 20 13 95". I then realized that the Bq79600 defaults to 1Mb/s baud rate so I updated that but am still seeing no activity or lights come on. R7 and R9 are populated with 0 ohms and R8 and R10 are de-populated. I am powering the EVM off 5V from the LAUNCHXL-F28379D dev kit and have the J1 and J3 jumpers set to 5V. J10, J11 and J12 are all set to UART.

What does it mean that the red D3 LED is on after I send the wake up pulse to Bq79600EVM? 

  • 0
    TI__Genius 17440 points

    Hi Braden,

    If the red LED is on that means there are faults present. This isn't cause for alarm; this is common when first waking the EVM. I suggest reading the fault_summary register to make sure there aren't any major issues. If not, go ahead and clear the faults. 

    Can you share how you are powering the BQ79616EVM and how it is connected to the BQ79600EVM? Sometimes I have seen that the devices will not wake if the power supply is too current limited. What may be happening is that the launchpad's 5V power supply cannot supply enough current for the VIF communication (it requires ~10mA). I also recommend probing CVDD to make sure it is within the datasheet specs (4.9V - 5.1V in active mode).

    Another good thing to check is that the BQ79600 COMH path is connected to the BQ79616 COML path, and that the DIR_SEL bit in the CONTROL1 register is set to 0.

    Best Regards,

    Kristin Jones

  • 0 in reply to Kristin Jones93
    Prodigy 150 points

    Hi Kristin, 

    Thanks for the quick reply. I had the Bq79616 powered from a desktop power supply of 40V connected from the PWR pin to the GND Pin. Then I have the COMH from the Bq79600 connected to the COML of the Bq79616. 

    I just grabbed another power supply and ran the Bq79600 on 5V and 12V and measured CVDD of 5V so the power doesn't seem to be the issue.

    Instead of sending the wake up command to CONTROL1, I tried to clear all the faults FAULT_RST = 0xFF first but I still see the red fault light on so it appears my commands are not being interpreted. Like I said, I verified that my serial data was correct at 250Kb/s but I have not probed it at 1Mb/s so I will verify that the data is still correct and go from there I guess. 

  • 0 in reply to Braden Sunwold
    TI__Genius 17440 points

    Hi Braden,

    Thanks for checking out the supplies. A quick check to see if the BQ79600 understands the communication is a read of any register. If you get data back then your command structure is okay, at least for the read command. If there's a fault still present when you try to reset them, the LED may not go off, because the fault will immediately be set again. 

    Best Regards,

    Kristin Jones