Alex Bell

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7 years, 8 months ago.

Generate 13.56MHz Sine Wave with FRDM K64F

Does anybody know if/how I can generate a 13.56MHz sine wave on the FRDM K64F and output it to the DAC? When I run the example code (https://developer.mbed.org/handbook/AnalogOut) in a loop only get 50Hz. Thanks

2 Answers

Tomislav Arnaudov
7 years, 8 months ago.

or you can use separate DDS (as example AD9951) chip / module

Accepted Answer

And send it the digital out/PWM signal?

posted by Alex Bell 12 Apr 2017

DDS is a circuit which you can controll trough spi/i2c on one side and it generate direct sine wave on other side with pwm is realy hard to make nice and smooth sine wave in such a high frequencies ... try to google datasheet to mentioned AD9951 ic :)

posted by Tomislav Arnaudov 12 Apr 2017
Erik -
7 years, 8 months ago.

There is no way you get a sine wave at that frequency. Only realistic option is using PWM for example to get it, and putting a low-pass filter after it to make it a bit sine like.

Thanks for replying. Why can't the K64F output a sine wave this frequency? Is the clock speed of the DAC not fast enough? Thanks

posted by Alex Bell 23 Apr 2017

Yes, it does not even get close to being fast enough. Remember you also need at least a few samples per period to get benefit from using the DAC over just using PWM.

posted by Erik - 23 Apr 2017