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external ADC and DAC

Robin_Hood
Prodigy 50 points


Hey guys,

I'm new to the MSP430. 

Is it possible to interface an external 16bit ADC and an external 16bit DAC with the MSP430( one of the MSP430 family)? 

The 16 output bits of the ADC should be transferred parallel to 16 IO's and enter the MSP430 parallel. Is this possible? 

And otherwise for the DAC?

Thank you

  • 0
    Mastermind 7395 points

    It depends on the speed of the external DAC / ADC

    Usually in these cases it is preferred to use a DAC/ADC with serial interface, like SPI.

    Regards,

    Avi

  • 0 in reply to Avi Chami1
    Prodigy 50 points

    Hi Avi,

    thank you for your reply. 

    i want use an ADC/DAC with 200kSamples - 1M-Samples

  • 0 in reply to Robin_Hood
    Prodigy 50 points

    Can you tell me why it is preferred to use a serial( SPI, I2C) interface?

    I thought a paralell interface is much faster. 

    Thank you

  • 0 in reply to Robin_Hood
    Mastermind 7395 points

    A parallel interface would have been faster... if the MSP430 had one.

    As far as I know, there aren't MSPs with external parallel buses.

  • 0 in reply to Avi Chami1
    Guru 46710 points

    Avi Chami1 said:
    As far as I know, there aren't MSPs with external parallel buses.

    Parallel bus can be emulated using port i/o, but I don't see msp430 as right choice to handle 16bit 1Msps ADC/DAC such way. 1Msps is quite high sample rate for 16..25MHz CPU, especially if DMA can't be used as in the case of msp430.

  • 0 in reply to Ilmars
    Prodigy 50 points

    Thanks for the reply IIImars,

    can you suggest me another microcontroller which fits for my project?

  • 0 in reply to Robin_Hood
    Guru 46710 points

    Well... Cant's say because I don't know anything about your project except ADC choice. This is insufficient. Main question - what is your project?

    Any continuous sampling? If bursts - then how many samples? How many ADC and DAC channels ? How many math operations per sample - if any?

  • 0 in reply to Ilmars
    Prodigy 50 points

    I want to digitalize 10 analog voltages coming from a positioning detector of a laser system. On the other hand I want to control some components of the system( eg. mirrors). I calculated that I need 16bit resolution for the DAC and ADC and 10:1 Multiplexer/Demultiplexer. Sampling rate of ADC/DAC 200kS\s - 1MS\s. 

    I'm a student and I do an internship, my task is to check which microcontroller and adc\dac's fit for this project. A lot of things are new to me. 

    Thank you for your patience.

  • 0 in reply to Robin_Hood
    Guru 46710 points

    Robin_Hood said:
    I want to digitalize 10 analog voltages coming from a positioning detector of a laser system. On the other hand I want to control some components of the system( eg. mirrors). I calculated that I need 16bit resolution for the DAC and ADC and 10:1 Multiplexer/Demultiplexer. Sampling rate of ADC/DAC 200kS\s - 1MS\s. 

    Check ARM and DSP microcontrollers then.

    Are you absolutely sure you need 16 bits? I am asking because TI ARM mcu's happen to have 12bit 1Msps ADC built-in.

  • 0 in reply to Robin_Hood
    Guru 227245 points

    Robin_Hood said:
    i want use an ADC/DAC with 200kSamples - 1M-Samples

    1M samples on 16 bit ADC means 16MBaud transfer rate. And, on 16MHz CPu clock, one word every 16 CPU cycles. What do you expect to do in these few 16 cycles?
    Of course you may read a bunch of data using DMA into a RAM buffer and then work on it while not sampling at all.

    But for conuous opearation, this sample rate makes no sense.

    Just a sanity check.

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