How to coordinate with Smartpin in NCO mode? IN not working?

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  • Reinhard wrote: »
    And probably the biggest mistake:
    I have not specified GND-ref and VCC-ref.
    As I see now GND-ref and VCC-ref is used to scale the raw adc to [mV]
    Can read the raw Values w/o scaling.

    Anyway
    Thanks
    @Ariba and @evanh

  • Yeah, it's not so easy at the moment. It's hard to follow the smartpin description, and you never know if it may be the compiler that has a bug.
    For example the _wrpin / _wxpin / _wypin in flex-C have the pin and value parameters in reverse order to the Assembler commands. Not sure if this is intentional, I had to check the listing to find that out.
    Cool is that flex-C allows underscores in binary constants (0b011_0000), like Spin does.

    You can for sure also use inline assembly instead of _wrpin, _dirl and so on, as you have done.

    My testcode reads the GND and VCC reference values only once at begin, for a serious program, you need to recalibrate them from time to time.
    It's amazing how stable the raw ADC value is with Sinc2 filtering, compared to other microcontrollers. Also at 13 bits resolution the values differ only marginally. But for an exact measurement you need to know the ADC value for 0V and 3.3V, they are not 0 and 1023 as you would expect with a 10bit SAR ADC.
  • Ariba wrote: »
    Cool is that flex-C allows underscores in binary constants (0b011_0000), like Spin does.
    yes , this is pretty cool.

    Ariba wrote: »
    My testcode reads the GND and VCC reference values only once at begin, for a serious program, you need to recalibrate them from time to time.
    thank you for this hint. Comes it from temperature effects ?

  • ReinhardReinhard Posts: 384
    edited 2020-01-23 - 17:15:25
    @Ariba , another question
    in your pinconfig (....) you set x = 9 for the adc
    void pinconfig(int pin, int mode, int x, int y)
    {
      _dirl(pin);
      _wrpin(pin,mode);
      _wxpin(pin,x);
      _wypin(pin,y);
      _pinl(pin);
    }
    
    count from 0 ... 9 is 10 counts
    is this the reason for 10bit adc ?

    with other words can I say adc - resolution = 2 ^ (x+1) (in a meaningful x-range)
  • @Rayman sorry for hitchhiking your thread, but I think the problems are similar.
  • Reinhard wrote: »
    @Ariba , another question
    in your pinconfig (....) you set x = 9 for the adc
    void pinconfig(int pin, int mode, int x, int y)
    {
      _dirl(pin);
      _wrpin(pin,mode);
      _wxpin(pin,x);
      _wypin(pin,y);
      _pinl(pin);
    }
    
    count from 0 ... 9 is 10 counts
    is this the reason for 10bit adc ?

    with other words can I say adc - resolution = 2 ^ (x+1) (in a meaningful x-range)

    Do you have the newest document, that describes the Rev-B silicon? There is a table on page 72, which shows possible resolution and sample modes you can set with the X value.
    Yes for 'SINC2 sampling' it's just the number of bits -1, you write into the X parameter. Works up to value 13, you have then 14 bits for the full range. But in praxis only a part of the full range fits into the -0.3V ... 3.6V that a pin can handle with an ADC gain of 1.
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