#include "math.h"



#define TRUE 1
#define FALSE 0
#define COUNT(some_array) ( sizeof(some_array)/sizeof(some_array[0]) )
#define M_PI 3.14159265358979323846



/*******************************************************
* Method related *
*******************************************************/
typedef struct tagV_CHANNEL
{
float Sum;
float K;
float Vdet;
float LastSample;
int nSamples;
int Active;

} V_CHANNEL, *PV_CHANNEL;


V_CHANNEL chanA;


void vChanPrepare(PV_CHANNEL pChan)
{
pChan->LastSample = -1;
pChan->nSamples = 0;
pChan->Active = FALSE;
pChan->Vdet = 0;
pChan->Sum = 0;
}

void vChanUpdate( PV_CHANNEL pChan, float CurrentSample )
{
// try to detect start of the positive sample to activate integrator
if (CurrentSample > 0 && pChan->LastSample <= 0)
pChan->Active = TRUE;

if (pChan->Active)
{
pChan->nSamples += 1;
pChan->Sum += CurrentSample;

// detect start of the negative sample
if (CurrentSample <= 0 && pChan->LastSample > 0)
{
pChan->Active = FALSE;
pChan->Vdet = pChan->Sum / pChan->nSamples / pChan->K;
pChan->Sum = 0;
pChan->nSamples = 0;
}

}

pChan->LastSample = CurrentSample;

}

/*******************************************************
* Signal simulation *
*******************************************************/
float Vref[ 240 ];

void BuildReferenceSignal( float Vrms )
{
for( int i = 0; i < COUNT( Vref ); i++)
{
Vref [ i ] = (Vrms / 0.707) * sin( 2 * M_PI * i / (COUNT( Vref) / 3) );
}
}


/*******************************************************
* ADC sampling simulation *
*******************************************************/
void RunAlg(void)
{
vChanPrepare( &chanA );

// feed reference data in.
for( int i = 0; i < COUNT( Vref); i++)
vChanUpdate( &chanA, Vref[ i ] );
}



/*******************************************************
* Does calibrating *
* and then estimating error of the *
* RMS calculation method w/o squares *
*******************************************************/
int main(void)
{
float err;

printf("Building reference signal Vrms=220V\r\n");
BuildReferenceSignal( 220.0 );
printf("Calibrating....");
chanA.K = 1;

RunAlg();

chanA.K = chanA.Vdet / 220.0;
printf("OK, K = Ves / Vref, K=%0.3f, Ves=%0.3f, Vref=%0.3f\r\n", chanA.K, chanA.Vdet, 220.0);


// now when K is calibrated, lets estimate method error on signals with diff rms (from 40V to 380V)
for( float i = 40; i < 380; i += 2.5)
{
BuildReferenceSignal( (float)i );

RunAlg();
err = abs( chanA.Vdet - i) * 100 / i; // error in percent
printf("Vref=%0.6fV, Vdet=%0.6fV, error - %0.6f%%\r\n", (float)i, chanA.Vdet, err );
}

printf("\r\nenjoy the simplicity, no squares no square root calculation, 0% RMS error ...\r\n");

return 0;
}