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TCAN4550EVM: spi communication

Ankit Rajput
Prodigy 10 points
Part Number: TCAN4550EVM
Other Parts Discussed in Thread: TCAN4550

Hey there,

I am using TCAN4550EVM and connected with host MCU interface through SPI. I am sending the Read sequence but in response I am not getting any signal output on MISO line.

Please look into the snapshot attached and resolve.

  • 0
    TI__Mastermind 33400 points

    Hi Ankit,

    Can you verify the voltage on the VSUP, VIO, and VCCOUT pins?  Also, can you verify the voltage on the RST pin?  It should be LOW for normal operation.

    If possible, can you provide a picture of the EVM so I can see the jumper and switch position settings?

    Thanks for the SPI Read plot.  Can you try reading register 0x0000 which is the Device_ID1 register?  It should have a default value of 0x414354.

    I'm curious to see if there can be any activity detected on the SDO (MISO) net.  This plot is of register 0x0820 which is an interrupt register that typically would return 0's unless interrupt bits had been set.  Register 0x0820 requires the digital core of the TCAN4550 to be functioning which requires both the power and the clock (crystal) to be good. 

    However, the Device_ID1 register only requires the device to have good power and does not require the clock (crystal) to be functioning.  This register only operates off of the SPI Clock.  Therefore, if we see a response from a read of 0x0000 and not from 0x0820, then this may indicate a clock (crystal) related issue.  However, it it too does not return a value, then there may be some other issue.

    If possible, can you also provide a picture of the EVM so I can see the jumper and switch position settings?

    Regards,

    Jonathan

  • +1 in reply to Jonathan Nerger
    Prodigy 10 points

    Hi Jonathan,

    Thank you for your response.

    The voltages on the desired pins are as follows:

    VSUP: 13.01V, VIO: 4.96V, VCCOUT: 9.28V, RST Pin: 0.1V.

    Please have a look at the attached picture of board.

    Moreover, I am reading the same response from Register 0x0000.

    Regards,

    Ankit

  • +1 in reply to Ankit Rajput
    TI__Mastermind 33400 points

    Hello Ankit,

    The VCCOUT voltage of 9.28V troubles me.  This is supposed to be a 5V LDO that has an absolute max voltage of 6V.  If the VCCOUT voltage really is 9.28V, then the device is likely damaged which is why it is not responding to your SPI messages.  Please double check the VCCOUT voltage and if it is high, then the TCAN4550 device will need to be replaced.

    Regards,

    Jonathan

  • 0 in reply to Jonathan Nerger
    Prodigy 10 points

    Hi Jonathan,

    Actually, the device got damaged not knowing specifically but probably there might be some transient voltage in input power supply (VBAT) that caused the failure. Although now I am able to receive the data on MISO line.

    I am receiving first byte either 'E0' or 'A0'. I want to know, what is the meaning of this byte? 

    Thanks & Regards,

    Ankit 

  • 0 in reply to Ankit Rajput
    TI__Mastermind 33400 points

    Hi Ankit,

    I'm sorry to hear that the device was damaged, but I'm glad that you have been able to make progress.

    On every SPI Read/Write transaction, the device returns the "Global Fault Flag status" on the first 8 SPI Clock cycles immediately following the SPI Chip Select signal transitioning low.  This is to allow the MCU to monitor whether any immediate attention is needed without requiring the MCU to read the full interrupt registers.  The Global Fault Flag is the same as register 0x0820[7:0].

    A value of 0xA0 has the CANERR and GLOBALERR flags set.  The CANERR bit is set either from a CAN Silent or CAN Stuck Dominant condition.  Likely you are also getting a CAN Silent error which occurs when no CAN bus activity is detected for approximately 1 second.  This bit will also set the GLOBAL Error bit.

    A value of 0xE0 has the additional WKRQ (Wake Request) bit set which indicates that the device likely woke up.

    None of these bits indicate a true error condition and I would say they are just bits used for information while you are getting the device up and running.  Once the device is up and running, a normal application may not want to see a CAN Error because this could indicate a problem with the device's ability to communicate on the bus.

    Regards,

    Jonathan