negative value Conversion.

dear all,

i have 2 angle desired , actual. negative . using qmodbus software read below data modbus slave. if value of desired put has + value  master read data in +ve value. if value assigned -ve . reading in image. if value selecting word -43 read. how convert readable format. instead of printing 65543 how make print either in +ve value or in -ve value


in below code checked if no negative multiply -1 else display is. -ve value displaying zero.
if hexadecimal , subtract ff value got add 1 actual no. since decimal no dint how it.

code: [select]


#include "glob.h"
#include "rtc.h"
#include "config.h"
#include"timecalc.h"

#define id   1

static int local_day=10;
static int local_month=4;
static int local_year=2014;
static int local_s=2;
static int local_h=13;
static int local_m=14;



int wind_speed=30;
int wind_kmph=67;
float desired_angle=-45.0;
float actual_angle=-43.0;

modbus slave(id, 0, 0);
boolean led;
int8_t state = 0;
unsigned long tempus;
// data array modbus network sharing
uint16_t au16data[14];


void setup() {

  // start communication
  slave.begin( 9600 );
  rtcsetup();

  tempus = millis() + 100;
  digitalwrite(13, high );
}


void loop() {
  // poll messages
  // blink led pin on each valid message
  state = slave.poll( au16data, 14);
  if (state > 4) {
    tempus = millis() + 50;
    digitalwrite(13, high);
  }
  if (millis() > tempus) digitalwrite(13, low );
  calctime();
  convertutctolocal();

  au16data[0]=local_year;
  au16data[1]=local_month;
  au16data[2]=local_day;
  au16data[3]=wkday;
  au16data[4]=local_h;
  au16data[5]=local_m;
  au16data[6]=local_s;
  au16data[7]=wind_speed;
  au16data[8]=wind_kmph;
if(desired_angle<0)
{

  au16data[9]=(int)desired_angle*-1;
  au16data[10]=(int)actual_angle*-1;
}else
{
au16data[9]=(int)desired_angle;
  au16data[10]=(int)actual_angle;
}

  au16data[11] = slave.getincnt();
  au16data[12] = slave.getoutcnt();
  au16data[13] = slave.geterrcnt();
}





au16data unsigned - how can hold negative value?

instead of working negative angles, why not work positive values?  remember, angles in circle, -1° same 359°, -2° 358°, etc.

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