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BQ79614-Q1: Not getting any responses from 2nd BQ79614-Q1 connected in daisy chain

Abhijith Kannan
Prodigy 70 points
Part Number: BQ79614-Q1
Other Parts Discussed in Thread: BQ79616-Q1

I have connected 2 BQ79614-Q1 in daisy chain configuration. The COMH of the base device is connected via Capacitor Isolation to the COML of the 2nd device. COML of the base device is left unconnected and the COMH of the 2nd device is connected to 1k resistor. Both devices wake up after the wake ping is given to the base device. I am able to successfully communicate with the base device but not with the second device. Here are the commands send to base device from the microcontroller :

90 00 03 09 20 13 95                                 // Wake Up Device 2
D7 03 43 00 00 00 00 00 00 00 00 61 6F  // broadcast write to write 0x00 to ECC_DATA1 to ECC_DATA8 registers
D0 03 09 01 0F 74                                     // broadcast write to set CONTROL1[ADDR_WR] = 1.
D0 03 06 00 CB 44                                    // broadcast write to DIR0_ADDR register with data 0x00
D0 03 06 01 0A 84                                     // broadcast write to DIR0_ADDR register with data 0x01
D0 03 08 02 4E E5                                    // broadcast write to set all devices to stack
90 00 03 08 00 13 DD                                // Set the base device
90 01 03 08 03 52 20                                 // Set the top of the stack
C0 03 43 07 BC D6                                    // broadcast read ECC_DATA1 to ECC_DATA8 registers
80 00 05 2D 00 28 8F                                // Data is received from base device
80 01 05 2D 00 29 73                                 // No data is received

Also the 2nd device wake's up even when 90 00 03 09 20 13 95 command is not send and also it does not goto shutdown even if i gave 90 00 03 09 40 13 BD to base device.

  • 0
    TI__Prodigy 440 points

    Good morning, 

    Thank you for reaching out to us. A few questions to better help you with your set up. Are you using the BQ79614 EVM? If so, does the issue also happen when you reverse the position of the EVMs? (i.e., Device 2 be the base and Device 1 top of stack) Please verify your components and isolation set up match the ones from the datasheet under section 10.2.1.2.7 Daisy Chain Isolation. It shows the isolation components for devices connected on the same PCB and on different PCBs.

    As for the device waking up without the wake command, check that the NPN Q1 or Q2 (depending on which one is populated) voltages are following the datasheet. This could have damaged the unit if not working properly. ESD damage could have also damaged the unit causing it to stop working as intended. 

    Best,

    Fernando Dominguez

  • 0 in reply to Fernando Dominguez
    Prodigy 70 points

    Its a custom PCB board. After reading through datasheet once more, I understood that, WAKE up ping propagates. So that explains why the 2nd device wake up soon after the wake ping is given. But don't understand why it isn't going to shutdown mode when I have instructed base device to send the shutdown tone. I could see the tone being sent to the 2nd device through the oscilloscope. I could also see the broadcast write commands being send to the 2nd device but when I send a single read command with device id 0x1, I get nothing in return. I did replaced the chip but I am getting the same result.

  • 0 in reply to Abhijith Kannan
    Prodigy 70 points

    Also I couldn't make the 2nd device shutdown using the broadcast write command D0 03 09 08 CF 72. Only device 1 shutdowns 

  • 0 in reply to Abhijith Kannan
    TI__Prodigy 440 points

    Good morning, 

    You state that you can see the tone being sent to the device. We would like to ask if we could see the logic analyzer logs from the receiving side of the second 79614 device to further debug this issue. There could be an issue with the timing of the commands, or the isolation components being used to communicate between devices. 

    Are you able to communicate to the second device individually? and/or set the second device as the base device? 

    Which microcontroller and program are you using to send these commands? 

    Best,

    Fernando Dominguez. 

  • 0 in reply to Fernando Dominguez
    Prodigy 70 points

    Oscilloscope : SDS 1202X-E
    Probe : 10x 1Mohm / 18pF

    I have upload Images of signals across COML pins of 2nd device when wakeup ping is applied to the base and when a goto shutdown broadcast write  command to control1 registers sent.

    https://drive.google.com/drive/folders/1rtkZ4zUSUuMojqaWU906SCYe_g4So544?usp=sharing

    I have also uploaded the schematics of the circuit.

    Please Note : Capacitors C112 to C118 have been removed from the PCB as its connected to the wrong ground. Also R14 is removed from the base device. 

    The STACK RX and STACK TX of the base device is connected to a VCCB (5V) channel output pins of the voltage translator NXB0104PW-Q100J.

    The commands is send by DSPIC33EP128GP504 to VCCA(3.3V) input pins of the voltage translator.

    As of now we are using BQ79614-Q1 instead of BQ79616-Q1 and 10 cells are connected to each BQ79614-Q1. So all other pins to which cells can be connected are left unconnected.

  • 0 in reply to Abhijith Kannan
    Prodigy 70 points

    I am able to communicate with the 2nd device when it is set as the base device. I connected another microcontroller to TX and RX of 2nd device (I replaced the 0 ohm to 100k and also added a 100k pull up resistors to TX pin) and I was able to assign it an address and read cell voltages of all connected cells.

  • +1 in reply to Abhijith Kannan
    TI__Prodigy 440 points

    Good morning, 

    Thank you for sharing this information. While reviewing your schematic, I noticed that you reversed the pin connection for COMLN and COMLP  

    This may be the root of the issue as why the device is not properly receiving the commands you are sending.

    Best,

    Fernando Dominguez. 

  • 0 in reply to Fernando Dominguez
    Prodigy 70 points

    It was indeed the problem. We reversed the PCB traces to COML of the 2nd device and we were able to communicate with the device. Thanks for the help.