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CC2530 Single-ended mode configuration

Jose Faria
Intellectual 510 points
Other Parts Discussed in Thread: CC2530

Hello,

I'm new in CC2530 and I'm facing some problems with ADC.

From the User's Manual we get:

"The digital conversion result is represented in 2s-complement form. For single-ended configurations, the
result can be expected to be positive. This is because the result is the difference between the input signal
and ground, which is always positively signed (Vconv = Vinp – Vinn, where Vinn = 0 V). The maximum
value is reached when the input signal is equal to VREF, the selected voltage reference."

So my main question is: How do I configure the single-ended mode?

I'm using AVDD reference voltage (2,5V). For V=142mV in the channel 2, I get only around 116 in the ADC (In 12 bits I'd expect twice). For V=~0V sometimes I get small negative values. This makes me believe that the ADC is, somehow, mid-scaled. Is it so?

I'm getting the adc result from:

  reading = (int16) (ADCL);

  reading |= (int16) (ADCH << 8);

  reading >>= 4;

I'd really apreciate some fast help.

Best regards,

Jose Faria

  • 0
    Intellectual 510 points

    Hello again,

    Anyone available to give me a hand?

    Many thanks in advance

    Jose Faria

  • 0 in reply to Jose Faria
    Guru 31280 points

    Hi,

    http://e2e.ti.com/support/low_power_rf/f/155/t/185525.aspx

  • 0 in reply to Igor Sherer
    Intellectual 510 points

    Thanks for your answer Igor,

    Your answer got me into a code example where I couldn't find a direct answer to my question. To continue my work, I assumed that there is not a way to configure single-ended mode bacause this is done when we choose the channel to read.

    As a consequence, in the single mode (that now I assume to mean "in a single-ended channel"), the result can give small negative values (this means that a 1bit is always spent to give us information about the sign of the result). There were no problems for me assuming this.

    My main concern is: When there are 0V in the ADC input, in some chips I get, for instance, the value "+"1 (which I consider to be acceptable) but in a different chip I get "-7" (considering a range a -4095 to +4095). I tried 3 different chips CC2530 and always got different result for 0V.

    Are theese differences between chips normal in CC2530?

    Thanks in advance,

    J. Faria

  • 0 in reply to Jose Faria
    Guru 735685 points

    Dears,

    It is normal to have little differences in ADC reading from different chips CC2530.

  • 0 in reply to Jose Faria
    Prodigy 60 points

    Hi, i face the same problem with Jose. It seems that the single ended conversion result is 1/2 expected value.