I want to make NMEA 0183 output COMPASS　

Projects Programming
1

I want to make NMEA 0183 output COMPASS using acceleration sensor
I want to build an angle with the following sketch and build NMEA0183 (nmea, $ HCHDG) HDG statement from the serial port.
What sort of sketch should I add?

[code]
#include <Wire.h> //I2C Arduino Library
#define address 0x1E //0011110b, I2C 7bit address of HMC5883
 
void setup(){
  //GY-273
  Serial.begin(9600);
  Wire.begin();
  Wire.beginTransmission(address); //open communication with HMC5883
  Wire.write(0x02); //select mode register
  Wire.write(0x00); //continuous measurement mode
  Wire.endTransmission();
}
 
void loop(){
     Serial.println(Angleread()) ;          // 方位角を返す
     delay(500) ;                            // 500ms後に繰り返す
}
int Angleread(){
  int x,y,z; //triple axis data
  Wire.beginTransmission(address);
  Wire.write(0x03); //select register 3, X MSB register
  Wire.endTransmission();
  Wire.requestFrom(address, 6);
  if(6<=Wire.available()){
    x = Wire.read()<<8; //X msb
    x |= Wire.read(); //X lsb
    z = Wire.read()<<8; //Z msb
    z |= Wire.read(); //Z lsb
    y = Wire.read()<<8; //Y msb
    y |= Wire.read(); //Y lsb
  }
  return atan2((x + 20) , (y + 20)*(-1)) * RAD_TO_DEG + 180;//40と20は補正値
}

[/code]

2

What sort of sketch should I add?

You need to do more with the value returned by Angleread() than just print it.

What are you sending the NMEA sentence to? What is the COMPLETE specification for the NMEA sentence you want to send? How often should you be sending that sentence? NOT "as often as possible" as your code would do now.

3

To build NMEA 0183 for heading (compass direction) there are two; one for magnetic, one for true, so first you need to know which one. If you are taking from a compass, I would say magnetic. The sentence structure is,

$ - message start
HC - Talker Identifier (HC = Heading - Magnetic Compass)
HDM - Sentence Identifier (HDM = Heading - Magnetic, HDT = Heading True)
x.x - Heading in degrees
M - M = Magnetic (T = True)
hh - checksum delimiter () and checksum (hh)
- message end

so the whole sentence would be

$HCHDM,x.x,M*hh

4

I would use the snprintf function, except that floating point is not supported by default on Arduino. To get around that use an integer for the heading, and after calculating the checksum, something like

char buf[20];
int heading = 238; //degrees
byte checksum = 0;
snprintf(buf,sizeof(buf),"$HCHDM,%d.0,M*%02X",heading,checksum);
Serial.println(buf);
5

No. There are many problems with that sketch.

Unless you always plan to be traveling on a heading of 238 degrees, you have to insert the actual heading, calculate a valid checksum, and insert that too.

The output part should be in the loop() function.

It looks to me like you need to review the basics of how an Arduino program is organized.

6

If you would like to have someone write the sketch for you, post in the Gigs & Collaborations forum section. You may be asked to pay for the help.