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BQ79731Q1EVM-060: SPI fail using TC377 demo board.

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Prodigy 20 points
Part Number: BQ79731Q1EVM-060

Hi,

We directly connect pins on TC377 demo board to 79731 EVM J16 (no stack device).

We use the same 5V pin on MCU as supply for EVM J16 and 5V_LV and use GND pin on MCU as ground for GNDLV.

The jumper selection follows the datasheet for SPI. And the rest of configuration is default.

We send WAKE ping (2750ms), and DVDD LED is on.

After 10ms, we send a single device read command to read REG 0x311

0x80 0x00 0x03 0x11 0x00 0xD9 0x8E

After delay 200us, we can not receive the response frame (only 0xFF).

Is any step missing in SW for communication?

Or any other points in HW configuration should be noticed?

Is there any effective way to analyze the problem?

We configure MOSI/MISO pins in PUSH_PULL mode and direct connect the MOSI/MISO pins between two boards without pulling up to VIO. Is this necessary?

The output state of the MOSI pin during idle is determined by the state of the last bit of data sent by the host. (Not always HIGH in idle).

     

       

Thank you in advance for your help.

  • 0
    TI__Expert 7020 points

    Hi Kunling,

    Chip Select should be pulled low for the whole duration the read frame and the response frame. The clock should also be sampling the response. 

    Pulling chip select back up indicates the entire frame has ended. Pulsing nCS in the moddle of a command frame is not supported.

    Master shall always drive MOSI to '1' when not sending cmd into device. This would mean that the output state TC377 state of idling its output as it's last output state would not be supported.

    J6 should not be populated as the following configuration for spi should be followed from the EVM user guide:

    Regards,

    David