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LMK04832: Device not responding to SPI commands

Part Number: LMK04832

Hi there,

I have been working with a custom development PCB that has an LMK04832 on board. I have been attempting to program the LMK04832 over SPI for a little while now, but have failed to get any response even from the simplest of tests.

I have fully verified that the chip is getting power and all of the SPI control wires are in the right places. I've stripped back my test as much as possible - the below scope outputs are from sending just two packets, 500 ms apart. All signals are 3.3 Vpk-pk and the SCLK is around 166 kHz. The first is the RESET cmd (write val 0x80 to addr 0x0000) and the second is simply trying to read back the value of the LSB of ID_PROD (expecting val 0x63 from addr 0x0005). As you can see, there is no response from the LMK04832.

I have also attempted to switch on an LED attached to Status_LD2, by writing value 0x04 to addr 0x016E (needing logic high, due to how it was wired), and also have monitored the power while shutting it down (POWERDOWN, writing value 0x01 to addr 0x0002), which made no change in the power consumption.

All of these tests lead me to believe that the LMK04832 IC is just not working on this board. Is there anything else it looks like I missed or that you suggest I test before I attempt to replace the IC?

Thanks for any help you can provide,

Anthony

  • Hi Anthony,

    We will get back to you the next business day.

    Regards,
    Hao

  • Hi Anthony,

    Any chance your RESET pin is asserted (high)?

    As long as RESET pin is high, the register state will be fixed in the reset state and you won't be able to program.

    73,
    Timothy

  • Hi Timothy,

    That's a very good question - thanks for pointing that out, I had not been paying attention to the RESET pin. Unfortunately, even after pulling it low, I still can't communicate with the device using the same two SPI commands as above.

    I don't have my power meter on me at the moment to check if changing the RESET pin state changes the current draw, but I will test that the next chance I get.

    Cheers,

    Anthony

  • Hello Anthony,

    Is there any way, like with a curve tracer, to confirm the solderdown of the IC is good?  Is this problem occurring on multiple boards, or do you just have the one?

    The plots you show above, you mention they are scope outputs... I don't see a voltage.  I presume this is some SPI bus analysis mode.  What is the threshold set to/what is the high voltage the waveform actually achieves?

    73,
    Timothy

  • Hi Timothy,

    Thanks for all of the help - I think my main issue was the RESET pin after all. I did some more testing today and it appears I was also having some issues with the programmer I was using, it seemed to be loading the SDIO pin more than it should've while taking input.

    After changing to another programmer and pulling RESET low everything was all sorted - which is really great to see. Thanks again for your help with this.

    Cheers,

    Anthony

  • Great Anthony,

    Glad to hear things are working for you.  If you have any different questions please open a new thread.

    73,
    Timothy