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MSP430F1611 ADC12 Sampling rate

MNK
Prodigy 10 points


First, I am very new to MSP430 programming so excuse my ignorance.

The problem: I am trying to sample four ADC channels using the internal 2.5V reference and external 6MHz crystal. My analog input voltage range is from 0-2.5V and 0 - 20Hz. I need to sample all four channels three times (i.e. each time I generate one of three "stimuli" on GPIO pins) and then send the results via UART to PC (via RS232).

Is this feasible/possible using the ADC12 in 1611? The best sampling I could achieve was for 0-1Hz analog signal and amplitude of about 2Vpp. I varied the sample-and-hold times as well as sampling periods but to no avail (I am using TimerA for period generation and ADC12SC bit for sampling/conversion).

Any help, hints, or comments (or sample code) would be greatly appreciated!

Thanks,

Mark

  • 0
    Guru 227245 points

    There are several reasons why it fails.
    The minimum conversion time you can get with SHTx and 12 bit resolution and 6MHz clock is 17/6M = 2.833µs = 353kHz. Single channel. For more than one channel, it goes a little bit own if you correctly programmed a sequence.

    However, there' smuch you can do wrong. Wrong sampling mode, wrong trigger (so you start only one conversion and not a chain), wrong clock selection, and, and, and.

    It's best you post your code here and someone ( me? ) will look onto it and perhaps tell you what's wrong.

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