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ADC10 MSP430F2274

Luca Apolito
Prodigy 90 points

Other Parts Discussed in Thread: MSP430F2274

hi people

I would need to transform a signal coming from a sensor to around 4 Mhz with positive and negative points in digital with the msp430f2274 climbed on on the eZ430-RF2500. I know that this ADC don't traformes negative values but with a offeset I can resolve such drawback.  Besides I should transfer the results of such transformation with a peripheral SPI, but initially I have started for trying with a normal peripheral UART. the problem that I have found in exit is that the transformed signal is alone that of the positive semiondes even if the signal comes figurative so that there is no negative values of the signal. The thing is that with the signal coming from the sensor I have this problem, instead if I try with a generic signal given by a generator of signals with offset, the conversion it perfectly happens.

Now explained my problem the question, it is: is the problem given by the ADC, from the peripheral one, from the speed of the sensor or from the program in matlab built for the visualization of the transformed signal? how can I resolve such inconvenience?

thanks in advance for your help.

Regards Luca

  • 0
    Guru 227245 points

    ADC conversion takes time. None of the MSPs has an ADC that is fast enough to sample values at 8MHz sampling frequency.

    The maximum conversion speed of the ADC10 is ~300kHz. So you simply cannot analyze any signal faster than ~150kHz. And even then, you'll have to be lucky to hit the peak value. Usually you'll need to oversample by 20 to 50 times to get a good representation of a waveform, including peak and zero crossing.

    Not to mention the problem of sending data. The maximum speed you can transfer data on the MSP is ~3MB/s. And then the CPU is 100% busy stuffing data to the SPI conroller.

    Luca Apolito said:
    the transformed signal is alone that of the positive semiondes even if the signal comes figurative so that there is no negative values of the signal.

    Sure of that? Maybe your level-shifting fails and cuts the negative parts before the shift. How do you shift the signal? What voltage range? What is your supply voltage?

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