'
' readADCtoArray(INPUT_PIN,Buffer(),buffersize,delay)
'
' "sampletime" is ~250 ticks. For debugging purposes.
'
' Return value is the time in ticks (core timer ticks = 2 CPU cycles =
' 41,666ns @48MHz, i.e. 24000 ticks = 1ms - theoretical) for
' 295 samples (buffersize).
'
' All buffer values are only raw integers. They need to be corrected
' depending on your voltage divider etc. with VCorr.
'
' Known issue:
' It seems the _measurment_ of time is not really correct (diff. ~15%)
' if we read the ADC too/very fast (without waitstates).
' I have no idea why. Maybe the core timer and ExtInp(pin) are somehow connect
'
' written 21-Oct-2015 23:57:37
'
CFunction readADCtoArray
00000000
27BDFFC8 AFBF0034 AFB70030 AFB6002C AFB50028 AFB40024 AFB30020 AFB2001C
AFB10018 AFB00014 00C08821 8C960000 8CF00000 40024800 8CC20004 0440001B
0000A021 00A09021 00009821 3C159D00 0000B821 8EA20018 0040F809 02C02021
AE420000 000217C3 AE420004 40024800 0050182B 1460FFFD 00000000 0282A021
40024800 26730001 8E220004 04400007 26520008 5457FFF0 8EA20018 8E220000
0053182B 5060FFEC 8EA20018 02801021 00001821 8FBF0034 8FB70030 8FB6002C
8FB50028 8FB40024 8FB30020 8FB2001C 8FB10018 8FB00014 03E00008 27BD0038
End CFunction

#define _SUPPRESS_PLIB_WARNING
#include <plib.h>
#include "cfunctions.h"

long long readADCtoArray(
       long long *chan,
       long long *array,
       long long *elements,
       long long *delay)
{
   unsigned int pin = *chan;
   unsigned int e,
                wait = *delay; //takes 248 ticks to read ADC @48MHz CPU speed
   unsigned int zero_ticks,
                current_ticks,
                sum_ticks=0;
                                         
   // set the core timer to zero (s. delay.c)
   asm volatile("mfc0 %0, $9": "=r"(zero_ticks));

   for(e=0;e<=*elements;e++) {
    array[e] = ExtInp(pin);//wait;
    do {// get the core timer ticks
         asm volatile("mfc0 %0, $9": "=r"(current_ticks));
       } while(current_ticks < wait);
    sum_ticks+=current_ticks;
    // set the core timer to zero (s. delay.c)
    asm volatile("mfc0 %0, $9": "=r"(zero_ticks));    
   }
return (sum_ticks); // return sum of ticks
}

'+--------------------------------------------------------------+
'|                     RMS convertor for MX170                  |
'+--------------------------------------------------------------+
' The RMS value of a signal is the R(oot)M(ean)S(quare) value.
' It is calculated by adding up the squares of the input signal
' The mean of these squares is rooted. This process is explained
' in the steps below.
' This example uses the ADC in the PIC32MX170 to measure the
' AC input signal. Output is displayed at a 16x2 LCD.

'----------------------  Defines -------------------------------
ADCpin = 23         ' ADC input pin
Total = 800         ' array size for measuring 220mSec @ 48MHz
Offset = 1.650      ' numeric offset at 3.300V
CalValue = 24.85    ' gain factor attenuator and AC coupling @ 50Hz

Option explicit
'------------------------- Dim Variables --------------------
Dim Sample!(Total)
Dim SumSQ!, Value!
Dim i%,j%,a%

'---------------------- Initialize hardware -------------------
SetPin ADCpin, AIN  ' initialize ADC
CPU 48              ' maximum speed for the MX170

'LCD
LCD init 4,5,6,7,2,26
LCD 1,1,"Samples =       "
LCD 2,1,"RMS =          V"


'--------------------------- Measuring ----------------------

Do
   'sample input signal
   For i%=1 To Total
     Sample(i%)=Pin(ADCpin)-Offset
   Next i%

   'find zero crossings
   i%=0:j%=Total-1
   'first zero crossing in array
   Do
     i%=i%+1
   Loop Until(Sample(i%)>0 And Sample(i%+1)<0)

   'last zero crossing in array
   Do
     j%=j%-1
   Loop Until (Sample(j%)>0 And Sample(j%+1)<0)

   'calculate SQUARES
   SumSQ!=0
   For a%=i% To j%
     SumSQ! = SumSQ! + (Sample!(a%)*Sample!(a%))
   Next a%

   'calculate MEAN
   SumSQ! = SumSQ!/(j%-i%)

   'calculate ROOT
   Value! = Sqr(SumSQ!)

   'display values on 16x2 LCD
   LCD 1,11,Str$(j%-i%)
   LCD 2,7,Left$(Str$(Value!*CalValue!),5)

Loop