On Mon, Feb 6, 2017 at 4:21 AM, <mesquita.rodrig...@gmail.com> wrote:
> Hello Mr. TJF
>
> First of All, thank you so much for providing support on real-time tasks
> using a low cost plataform.
> I'm trying to apply the libary "libpruio" to make a system for energy
> meansurement using the beaglebone black. To do this, I need to enable 2
> ADC channels, set a sample time, fil a buffer with the samples and make
> some calculation that includes the FFT. I'm really newbie on
> microprocessors, but i wrote a simple C code. The idea of this code is just
> to make 128 samples os the two channels and print the values. Just it:
>
> #include "unistd.h"
> #include "../c_wrapper/pruio.h" // include header
> #include "time.h"
>
>
> //! The main function.
> int main(/*int argc, char **argv*/)
> {
> float n[256];
> int a[256];
> int i=0;
>
>
> pruIo *io = pruio_new(PRUIO_DEF_ACTIVE, 0x98, 0, 1); //! create new
> driver structure
> pruio_adc_setStep(io, 9, 1, 0, 0, 0);
> // step 9, AIN-0
> pruio_adc_setStep(io, 10, 2, 0, 0, 0);
>
>
> if (pruio_config(io, 128, 9<<10 , 156250, 4)){ // upload (default)
> settings, start IO mode
> printf("config failed (%s)\n", io->Errr);}
> else {
>
>
> if (pruio_rb_start(io)) printf("rb_start failed (%s)\n", io->Errr); //
> start measurement
>
>
> else{
> sleep(1);
>
>
> i=io->DRam[0];
> a[i] = i;
> n[i] = io->Adc->Value[i];
> do{
> if(i != io->DRam[0]){
> i=io->DRam[0];
> a[i] = i;
> n[i] = io->Adc->Value[i];
> }
> }while(io->DRam[0] < 126);
> a[io->DRam[0]] = io->DRam[0];
> n[io->DRam[0]] = io->Adc->Value[io->DRam[0]];
>
> for(i = 0; i<=127; i++ ){
> printf("amostra %d ----- %f \n",
> a[i], (n[i]/65536)*1.8);
> }
>
> }
> /* we're done */
> }
> pruio_destroy(io); /* destroy driver structure */
> return 0;
> }
>
> Right from the start I see several problems with your code.
125 zero based indexes. Or is it 128 ? Or do you really want 127 indexes ?
It's impossible for us to know.
do{
. . .
}while(io->DRam[0] < 126);
This is inconsistent with:
for(i = 0; i<=127; i++ ){
. . .
}
So, I have no clue what io-DRam[] *is*, but I can assume, somehow, you're
storing ADC values in DRAM *somehow* Based on your comments. However, first
off, your indexes to not match one another from buffer "packaging" to
buffer "unpacking". Secondly, you're not clearing your buffers(arrays)
before using them. This is what the "garbage" numbers are coming from. It's
just random values in memory, which by the way is very bad from a couple
perspectives. But this also leaves these arrays without a NULL termination
at the end. Which is very unsafe, as a potential stack overflow. At least
this applies for type char[], I'd have to double check the C standard that
you're using for your particular case to make sure. Which you can do more
easily than I.
Additionally, your code is hard to follow. With variable names such as a,
n, and i, and zero helpful comments. The code is not exactly self
documenting. But here is what seems to be happening. You're only storing
one ADC channel value into the first half of your array. Or maybe the
conditional if statement is testing for this somehow( unclear ), and taking
care of that ?
Assuming what you really want is 128 samples of the two ADC channels you
mention, your code needs to change. You need to check and make sure you're
never going to overflow from your arrays. Which may mean your arrays need
be of size 256 + 1 for each given type. Secondly, your loops need to be
consistent at whichever number of values you wish to store. Thirdly, you
need to clear your arrays before you use them, which can be done at array
initialization, or by using memset(), after initialization.
A couple of things worth mentioning. In your printf() statement I'm not
sure of libpruio's implementation, but from my experience with the
beaglebone's ADC, this does not seem right ---> (n[i]/65536)*1.8) Values
output from the ADC are in range 0-4095, I'd double check to make sure that
is correct. It could be that libpruio's values are different in
implementation through some sort of conversation. Secondly, for some
reason, it may become readily apparent that your index value may contain a
lot of zero's in the middle indexes. You're going to need to look into why
that it happening after you clean your code up some. As I said above. I am
not familiar with libpruio's implementation, and the rest of your code is
not clear enough to make a determination at a glance.
--
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