#include "PString.h"

int VaneValue;// raw analog value from wind vane
int Direction;// translated 0 - 360 direction
int CalDir;// converted value with offset applied
int LastValue;

#define Offset 0;

byte getChecksum(char* str)
{
    byte cs = 0;
    for (unsigned int n = 1; n < strlen(str) - 1; n++)
    {
        cs ^= str[n];
    }
    return cs;
}

/*=== MWV - Wind Speed and Angle ===
 *
 * ------------------------------------------------------------------------------
 *         1   2 3   4 5
 *         |   | |   | |
 *  $--MWV,x.x,a,x.x,a*hh<CR><LF>
 * ------------------------------------------------------------------------------
 *
 * Field Number:
 *
 * 1. Wind Angle, 0 to 360 degrees
 * 2. Reference, R = Relative, T = True
 * 3. Wind Speed
 * 4. Wind Speed Units, K/M/N
 * 5. Status, A = Data Valid
 * 6. Checksum
 *
 */
void printWindNmea()
{
    char windSentence [30];
    float spd = 0;
    byte cs;
    //Assemble a sentence of the various parts so that we can calculate the proper checksum

    PString str(windSentence, sizeof(windSentence));
    str.print("$WIMWV,");
    str.print(CalDir);
    str.print(".0,R,");
    str.print(spd);
    str.print(",N,A*");
    //calculate the checksum

    cs = getChecksum(windSentence);
    //bug - arduino prints 0x007 as 7, 0x02B as 2B, so we add it now
    if (cs < 0x10) str.print('0');
    str.print(cs, HEX); // Assemble the final message and send it out the serial port
    Serial.println(windSentence);
}


void setup() {
LastValue = 1;
Serial.begin(9600);
}

void loop() {
VaneValue = analogRead(A7);
Direction = map(VaneValue, 0, 1023, 0, 360);
CalDir = Direction + Offset;

if(CalDir > 360)
CalDir = CalDir - 360;

if(CalDir < 0)
CalDir = CalDir + 360;

// Only update the display if change greater than 2 degrees.
if(abs(CalDir - LastValue) > 2)
{
//Serial.print(VaneValue); Serial.print("\t\t");
//Serial.print(CalDir; Serial.print("\t\t");

LastValue = CalDir;
}
printWindNmea();
}