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Problem in calculation of sampling frequency using TIMAC

Other Parts Discussed in Thread: TIMAC, MSP430F5438, CC2520

Hi,

I am working on TIMAC. I am using MSP430F5438 experimenter board and CC2520 trans receiver.

I am sending a  sine wave signal from transmitter and reconstructing the digital signal on receiver side on pc by sending the data through UART.

I have taken following settngs:

System Clock: 12MHz

ADC Sampling rate: 5791Hz

UART Baud Rate: 460800

Number of data bytes per packet : 2

Wait period between two packets: 6ms

On python to perform fft I have taken timestamp as 0.0048sec ( means 208.33Hz sampling frequency)

I am getting good signal upto 30Hz.

My doubt is that all these parameters which I have set although serve my purpose but I am not able to determine a relation between them.

For eg. I should have taken timestamp( inverse of sampling frequency) on python as either 5791Hz or according to transmission rate as 333.33Hz but I am getting wrong frequency so to get the peak at correct position I took the timestamp as 208.33Hz.

Please can anyone suggest me where I am going wrong?

Thanks

  • Hi Pratap,

    I hope someone from the forum will help you on this.

    But as you know this is a zigBee/TIMAC/6LoWPAN forum, I would like to point you to wiki page http://en.wikipedia.org/wiki/Fourier_transform which may be useful for study.

    Regards,

    Suyash Jain

  • Hi Suyash,

    Thanks for the reply.

    Can you please explain me one thing that what is the relation between ADC sampling rate and the transmission rate( which is dependent on wait period and number of data bytes in packet length).

    I am asking this because if I take ADC sampling rate equal to TRANSMISSION rate then the wave which I reconstruct at receiver in not proper( it gets clipped and also there are some abnormalities in between too) but when I take sampling frequency around 5791Hz then I get good wave.

    Also if I take sampling frequency even higher around 10K then wave starts getting distorted even bad than when the sampling frequency was low ( 360Hz equal to transmission rate)

    All these settings are on controller side and they have got nothing to do with python script. So can you please help me understand this part.

    Thanks

    P.S. : one more thing my name is yuvraj not pratap