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Synchronous start of conversion for several MSP430AFE222

Vyacheslav Prokopiy
Expert 1305 points
Other Parts Discussed in Thread: MSP430AFE222

Hello.

I'm going to design a precision device for measurements. I would like to implement this device on several MSP430AFE222.

Device will contain 4 items of MSP430AFE222. Each of the ICs will measure 2 channels. I need to sample and convert several input signals - up to 8 - simultaneously with minimal possible delay between start of conversion event on every MSP430AFE222. In ideal case - without delays at all.

So, it seems, that I must implement a common clocking system for all of 4 MSP430AFE222 to make all of SD_24 modules work in synchronous mode with minimal delays between starts of conversion on each of them.
Are my conclusions correct and whether there are other ways to start A-D conversions simultaneously?

If so, where I can find some recommendations on how to implement a common clocking scheme for several MCUs? Or what is the alternative method to resolve my problem?

  • 0
    Guru 243110 points

    It is certainly possible to use a clock signal instead of crystal (just connect it to XIN).
    The SD24_A module also can use the external TACLK signal as clock (if you don't want to run the rest of the chip from the same clock).

    As far as I can see, the SD24_A cannot trigger the ADC from an external signal.
    It might be possible to synchronize the actual conversion start by disabling the ADC's clock signal until the SD24SC bits of all four chips have been set.

  • 0
    Guru 46710 points
    You shall run one chip on XT2 oscillator, output it's clock on "SMCLK out" pin and run " slave chips" in external clock source from this signal.

    Unfortunately I can't think of truly hardware-way to start all the ADC's simultaneously, thou you could think of using GPIO interrupt signalling - to start all ADC' s including master, in the GPIO ISR. It could be so that error is no more than one ADC clock period which possibly is acceptable for desired application.

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