#include <Adafruit_BMP280.h>
#include <Wire.h>
#define NMEA_TALKER_ID "WI" // Weather Instruments
#define NMEA_DELAY 10 // Send data every 10 seconds
// meters above mean sea level
#define ALTITUDE 1
// How many samples to take per iteration
#define PRESS_OVERSAMPLING 3
Adafruit_BMP280 pressure;
void setup() {
// put your setup code here, to run once:
Serial.begin(4800);
if (init_pressure() != true) {
nmea_txt("BMP280 init fail");
exit(1);
}
nmea_txt("Nanobaro ready.");
}
int init_pressure() {
if (pressure.begin()) return true;
}
const byte buff_len = 90;
char CRCbuffer[buff_len];
byte nmea_crc(String msg) {
// NMEA CRC: XOR each byte with previous for all chars between '$' and '*'
char c;
int i;
byte crc = 0;
for (i = 0; i < buff_len; i++) {
crc ^= msg.charAt(i); // XOR
}
return crc;
}
void nmea_send(String sentence, String params) {
String msg = String(NMEA_TALKER_ID) + sentence + params;
msg.toCharArray(CRCbuffer, sizeof(CRCbuffer)); // put complete string into CRCbuffer
int crc = nmea_crc(CRCbuffer);
if (crc < 16) msg += "0"; // pad with leading 0
String hexcrc = String(crc, HEX);
hexcrc.toUpperCase();
Serial.println("$" + msg + "*" + hexcrc);
}
void nmea_txt(String text) {
nmea_send("TXT", ",01,01,01," + text);
}
void loop() {
String s;
float temp, press;
temp = pressure.readTemperature();
press = pressure.readPressure();
s = "";
s = ",C," + String(temp) + ",C,TEMP";
s += ",P," + String(press / 1000.0, 5) + ",B,BARO"; // OpenCPN doesn't seem to grok Pascal (unit "P"), only Bar ("B")
nmea_send("XDR", s);
// These NMEA 0183 sentences are deprecated:
//nmea_send("MTA", "," + String(temp) + ",C");
//nmea_send("MMB", ",0.0,I,1.5,B");
delay(NMEA_DELAY * 1000);
}