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Reg: toggle frequency of GPIO pins on MSP430F5529 ...

zubin kumar
Prodigy 40 points
Other Parts Discussed in Thread: MSP430F5529

Hi all. 

I was using the MSP430F5529 eval board and I had set the mclk to around 33 MHz. What I am trying to do is toggle a GPIO pin (or any other pin) on the  micro at a frequency as close to 20MHz as possible. The code I use for toggling is - 

for (; ;)

P1OUT ^= BIT0;                          

One of the previous posts say that the for and the toggle statement will take around 12 to 15 cycles to execute so the max. toggle frequency I am looking at is 33/15 = around 2 MHz. 

I know this is a limitation of the micro, but is there any other way of increasing the toggle frequency of the I/O pins to bring it upto 20 MHz, maybe like using a timerA on an I/O pin etc.? I know I can set the MClk to 20MHz and bring it out on a pin, but I need to do some more calculations with the toggle freq. (phase shift etc.) so I need to toggle a GPIO pin that I can control easily by keeping it in a for loop.  Also, is 50MHz the max. MClk freq for the MSP430F5529?

Do let me know. Help will be greatly appreciated ...

Thanks ...

z.

  • 0
    TI__Expert 6140 points

    Zubin,

     

    Firstly that device is spec'd to run no faster than 25 MHz so running the part at 33MHz is out of spec.

    If you would like to toggle a pin as fast as possible I would use a timer in a PWM fashion. Please see the various code examples we have to implement something like this:

    http://www.ti.com/litv/zip/slac300d

    If you would like a faster toggle rate take a look at the MSP430F51x1/51x2 devices which have two TimerD units supporting up to 256MHz operation.

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