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Crystals for CC2540 does not work

user4299831
Prodigy 20 points
Other Parts Discussed in Thread: CC2540

I designed and made a CC2540 board following TI's reference design. 

However, CC debugger does not recognize the chip. When I checked the board, I found the crytals(both of 32.768kHz and 32MHz) does not oscillate. 

I have connected 9th pin of CON1(from debugger) to ON_VBAT, and power seems work properly.

All power pins come 3.3V, 30th pin comes 1.232V, 40th pin comes 1.8V. 

When I check 32kHz crystal, pin 1 and 2 are high, but does not oscillate.

And 32MHz crytal, pin 2 and 4 are connected to ground, and pin 1 and 3 are just low..(but not connected to ground). 

still it does not oscillate. 

Could you please check the schematic and give me a advice...?

I have no idea why the oscillator does not work....T.T

CC2540_v1.pdf

  • 0
    TI__Mastermind 29650 points

    Hi,

    The crystal oscillators will not be enabled when there is no program running on the device.

    You might have an error for VDD_SOC in your schematic. This should be the same supply as your DVDD connections and should be connected to ON_VBAT. As the schematic is right now this pin is floating though you will probably see a voltage on it due to leakage through the ESD diodes from other supply pins on the board.

    Edit:

    I didn't see that VDD_SOC was connected already. The schematic looks OK so it is hard to say what is wrong here. I would double-check the connections to the debugger and make sure you don't use too long cables (try keeping them <15cm). 


    Regards,
    Svend

  • 0
    Prodigy 20 points
    Dear Svend,

    Thank you for rapid check and kind reply.
    I just found the error in my schematic !!
    I connected the reset_n to a pull-up..and that makes the debugger cannot reset or connect my CC2540..
    I removed R3 which is 0 ohm res, and the board works properly.
    Anyway, Thank you so much! and have good day!

    -Jin-
  • 0 in reply to svendbt
    Intellectual 425 points
    Hi Svend,
    I have the same problem with both crystals not working. It sounds like I need to program the device to make them work? Is the chip not programmed when it comes from the factory? Do I need to program it for the crystals to turn on?

    thanks very much!
  • 0 in reply to Yoo Hsiu Yeh
    TI__Mastermind 29650 points

    Hi Yoo,

    When the chip is unprogrammed it will power up into ROM boot loader mode. No crystals will be enabled before application software enables them.

    Edit: The CC2540 does not have ROM boot loader. The rest is still true, without any application code, the device will not fire up the crystals.


    Regards,
    Svend

  • 0 in reply to svendbt
    Intellectual 425 points
    thank you very much! this means i don't have to try to debug the crystals not working, at least not until after i have flashed a program onto the device. thank you for clarifying.