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processor with two UART and two CAN interfaces

aim
Prodigy 140 points

Hi,

     I am doing a project on developing Universal Analog Input Module(with four channels,each channel capable of accepting inputs from thermocouple,RTD(2,3 and 4 wire),upto ±10V bipolar analog voltage input and 4 to 20mA current input.I need to select a microcontroller that has two UART and two CAN interfaces.I am planning to use a  Σ-Δ ADC in the circuit.So can you help me regarding the microcontroller selection?

Regards,

Divya

  • 0
    TI__Guru**** 244400 points

    Hello Divya,

    The TM4C123 devices have 5V tolerant IO's. But it does not mean that it will correctly for 5V sensing. You will need to scale down the range to 0 to 3.3V. TM4C123 has 3 CAN's and more than 2 UART's for use. The ADC is 1MSPS unless there is a requirement for your project of higher sampling rate.

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Prodigy 140 points

    Hi, 

         Thanks for the fast reply.But TM4C123 is a DSP processor right?Can you help with some other processors other than DSP processors?Besides ,I am planning to use a Σ-Δ  ADC ,which would be good for thermocouple measurements.So,what about the on chip ADC on the processor?

    Regards,

    Divya

  • 0 in reply to aim
    TI__Guru**** 244400 points

    Hello Divya

    TM4C123 is not a DSP processor. It is a Cortex M4F processor

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Prodigy 140 points

    Hi,

         Thanks for your quick response.I require a Σ-Δ ADC for precision thermocouple measurements.Is the ADC of TM4C123  of Σ-Δ type?Or is it possible to use a Σ-Δ ADC separately ?If so,what about the ADC of TM4C123?Please help.

    Regards,

    Divya

  • 0 in reply to aim
    Guru 27665 points

    Why so insistent on sigma delta?

     

    Other than, perhaps, lab assignments I've not seen a valid case for specifying conversion architecture ahead of converter performance characteristics.  And all architectures have advantages and drawbacks,  Implementations even more so.

    Usually the better questions to ask are about speed, resolution, accuracy (yes, that's a different parameter), linearity, interfaces (both analog and digital) and cost.

    Robert

  • 0 in reply to Robert Adsett
    TI__Guru**** 244400 points

    Hello Divya

    It is a SAR ADC. As Robert mentioned very aptly, there are more criteria's to select an ADC than just the architecture. It depends on the application requirement you plan to develop.

    If you still need a sigma-delta, then you can interface using I2C or SPI and external ADC. Again selecting the external ADC will depend on the application requirements.

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Prodigy 140 points

    Hi,

         Thanks.Σ-Δ ADC(with on chip PGA. Eg:AD7193) would help in precision thermocouple measurements,right?

    Regards,

    Divya

  • 0 in reply to aim
    TI__Guru**** 244400 points

    Hello Divya,

    Back to the basic question. Does it meet the application requirement in terms of SNR, linearity, speed of conversion.

    Regards

    Amit

  • 0 in reply to aim
    Guru 27665 points

    You might get more precise than some other unspecified A/D but not necessarily more accurate.

    Also you are dealing with temperature so the immediate question is how accurate and stable is your source?  Not much sense going to extra trouble to get 16 bits of accuracy if the source is only good to 8.  Check up on the accuracy of your thermocouple, I doubt that it justifies a highly accurate measurement subsystem.  I would not be surprised if 10 bits was more accurate than the sensor supported.

    A few notes on your selected A/D.  First it has a PGA.  That in combination with the conversion architecture suggests that it is optimized for dynamic range (indeed the data sheet title also suggests that).  Thermocouples do not have a wide dynamic range.  You would be better off with a thermocouple specific amplifier arrangement.

    Second, like many A/Ds it relies on an external reference for accuracy. It is difficult to find references better than 12 bits accurate, indeed there is a good chance they will be more expensive than the A/D.  You will note that this A/Ds data sheet's application section neatly sidesteps the issue of reference accuracy  by turning the whole system into a ratiometric conversion so they do not need absolute accuracy.

    At one time TI offered a course on A/D, D/A etc.. Other companies have as well.  If you get a chance I suggest you take the opportunity.  There is a lot more to A/D conversion than the converter.

    Robert