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Three simultaneous or not task

felipe paulo
Intellectual 410 points

Other Parts Discussed in Thread: MSP430G2553

I need do this:

1º : execute one table with values that will upgrade pins of msp and with external dac will compose one sine wave

2º read one keybord 4x4 that will indicate the output frequency

3º show the frequency value in lcd

I can do this task separated, but i can´t do this without harming the sine wave because in right interval of time the msp will not goes upgrade the pins.


How I can do it?

  • 0
    Guru 227245 points

    Yes, undistorted DAC output is not easy.

    You don't write which MSP you use. Many MSPs have a DMA channel available. You can use it to transfer one byte or word triggered by a timer from memory to DAC (or port pins).
    If you allow the DMA to interrupt a processor instruction, the transfers will go without any jitter. And the other tasks are not time-critical.

    However, the update of the external DAC must be doable with a single transfer to make it work. So no 'output new value, then pull and release trigger signal' type of DAC programming.

  • 0 in reply to Jens-Michael Gross
    Intellectual 410 points

    one RTOS can do this tasks?
    exist RTOS for msp430g2553?

  • 0 in reply to felipe paulo
    Guru 227245 points

    felipe paulo said:
    one RTOS can do this tasks?

    Well, an RTOS can manage multiple threads of execution. However, it rather adds to jitter and latency due to the organizational overhead.

    felipe paulo said:
    exist RTOS for msp430g2553?

    With only 512 bytes of ram, there is not much 'working space' for an OS. Especially fo multi-threading, which requires multiple stack areas. Maybe you can compile an RTOS for thsi chip, but I dubt there's much space left to actually do anything on this MSP then.

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