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Using only one crystal to run CC2500 and MSP430F2274

Yu Zhang10589
Expert 1100 points

Other Parts Discussed in Thread: MSP430F2274, CC2500

Hi all:

I am planning to run CC2500 and MSP430F2274. Up to now, I think I need to connect GDO0 to Xin and GDO2 to Xout. My question is: what are the register values for GDO0 and GDO2?

For GDO0, I am sure it will be 0x3F (CLK_XOSC/192), not sure what value I should write for GDO2.

Can anyone help?

Thanks

  • 0
    TI__Guru 65000 points

    It is unclear what you are trying to do.  There is an example circuit from the eZ430-RF2500 kit in the eZ430-RF2500 Development Tool User's Guide (SLAU227).

    In addition, the Wireless Sensor Demo (SLAC139) on the eZ430-RF2500 Product Folder would have examples of how to configure the MSP430F2274 registers relative to the eZ430-RF2500 kit.

  • 0
    TI__Genius 16215 points

    There is no options of wiring an external crystal to the eZ430RF because GDO2 is a dedicated output pin and you cannot insert an external crystal.

    However, there is a solution of using the output of the divided clock from the CC2500 GDO0 pin. GDO0 (CC2500) pin is hardwired to XIN (MSP430) pin. At reset, the CC2500 will output a 135-141kHz clock out on GDO0. The eZ430RF will output 135kHz because it uses a 26MHz cyrstal. By default, it divides the clock down by 192, which can be adjusted in software. This is a very stable clock out. You can use that clock as an input to the MSP430.

         P2SEL |= 0x40; // configure XIN (P2.6) by setting the SEL

    In this case, you don't have to configure XOUT.

    Regards,

    William

  • 0 in reply to William Goh
    Prodigy 30 points

    Hi!

    How could I change the divider from 192 to 4? The max input frequency on the MSP is 12MHz isn't it? Is not possible to use the pure 26MHz, right?

     

    Thanks!

  • 0 in reply to Vitor Silva
    Prodigy 210 points

    Hello, I was wondering the same thing... How can I change the prescaler value from 192 to 6?

    Thank you!

    Julie

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