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ADC to DMA example for Delfino F28335

Adre Neethling
Prodigy 60 points
Other Parts Discussed in Thread: CONTROLSUITE

Good day

Needless to say, I am new at CCS and I am just running through some of the examples that come with controlSuite. One of these examples is the ADC to DMA  conversion example:

Original source by: M.P.
TI Release: DSP2833x/DSP2823x C/C++ Header Files V1.31
Release Date: August 4, 2009

I've read through the description in "Example_2833xAdcToDMA.c" and configured the clock in the correct way. I have connected my analog supply to pin A0. According to the description, I should watch the "DMABuf1" variable. Only problem is, when I debug, that variable doesn't show up as one I can watch.

And when I select the ADC_Result registers to watch, I can see that it initializes to a value. But when I run the program, I get the following error: "Error: unable to read".

So, my question has two parts: Firstly, which register/variable should I watch in order to see the result of the A to D conversion and secondly, what can I do to solve the "Error: unable to read" error?

Regards

Adre Neethling

  • 0
    Prodigy 60 points

    Nevermind, I figured it out after some time.

    However, I have run into a new problem. According to your datasheets, the ADCResult register's value should not exceed 4096, yet I get 51520, for an input voltage of 2.3 V. I am currently "exploring" the functionality of the spra958k.zip examples. Thus, I am running the ADC on the non_Bios flash example.

    Regards

    AD Neethling

  • 0 in reply to Adre Neethling
    TI__Guru 60865 points

    The values in the ADC result registers are left aligned.  Your 51520 is 0xC940 in hex.  Take the left 12 bits and you get 0xC94, which is 3220 in decimal.  Convert this to voltage by doing (3220/4096)*3 = 2.358V, which is close to what you expected.

    There are also ADC result mirror registers, which are right aligned.

  • 0 in reply to Devin Cottier
    Prodigy 60 points

    Thank you for the speedy reply. I also just realized that the ADC might be set up for 16-bit conversion. Doing the calculation yields the same result. Sorry for not thinking... I did bad and I should feel bad.

    By the way, thank you for the excellent examples (especially spra958k). They really help alot.

    Regards

    Adre Neethling