ESP32 cansat next

Introduction

Some interesting coding stuff

snprintf

printf, print

Each ASCII character takes 1 byte. You can store exactly 128 ASCII characters in the above char array.

char report[128];  
  memset(report, 0, sizeof(report));
  snprintf(report, sizeof(report), "%4.2f, %4.2f, %4.2f, %4.2f, %4.2f, %4.2f",
    ax, ay, az, gx, gy, gz);
  Serial.println(report);

To have more JSON data structure use

 snprintf(report, sizeof(report), "{\"time\": %d, "
                                   "\"ax\": %4.2f, \"ay\": %4.2f, \"az\": %4.2f, \"temp\": %4.2f, \"p\": %4.2f, "
                                   "\"lat\": %8.7f, \"long\": %8.7f, \"alt\": %4.2f, \"speed\": %4.2f, "
                                   "\"so2\": %4.2f },", 
    treset, 
    ax, ay, az, t, p, 
    lat, lng, alt, speed,
    so2 );

but there is a small problem with array of JSON.

Radio

To send strings, use sendData( str ); command.

SD Card

First, open the file const String filepath = "/filename.csv"; and then append the data and linebreak

  appendFile(filepath, data);
  appendFile(filepath, "\n");

Simple code

A simple code to read data and send that via radio and store to SD card.

Declare

First declare the variables:

#include <TinyGPS++.h>
#include "CanSatNeXT.h"

#define GPS_BAUDRATE 9600  // The default baudrate of NEO-6M is 9600
TinyGPSPlus gps;  // the TinyGPS++ object
const String filepath = "/filename.csv";

long tradio = 0;
long treset = 0; //Time from reset
float ax;
float ay;
float az;
float t;
float p; 
float lat = 0;
float lng = 0;
float alt = 0;
float speed = 0;
float so2;  // Connect to pin 33

Initialize

Start the serial monitor, and software serial. Find the GPS module and start CanSatInitialization. Note that the radio needs a number in parenthesis.

void setup() {
  Serial.begin(9600);
  Serial2.begin(GPS_BAUDRATE, SERIAL_8N1, 16, 17);

  Serial.println(F("ESP32 - GPS module"));
  Serial.println(F("Lat, Lon, Alt, speed [m/s], Datetime"));

  // Start all CanSatNeXT on-board systems.
  CanSatInit();
}

Read data

Using the loop() method, read the data. Update the GPS only if there is new data.

void loop() {
  //Get the data
  treset = millis();
  ax = readAccelX();
  ay = readAccelY();
  az = readAccelZ();
  t = readTemperature();
  p = readPressure(); 
  so2 = analogRead(33);  // Connect to pin 33

  if (Serial2.available() > 0) {
    if (gps.encode(Serial2.read())) {
      if (gps.location.isValid()) {
        lat = gps.location.lat();
        lng = gps.location.lng();
        alt = gps.altitude.meters();
      } 
      if (gps.speed.isValid()) {
        speed = gps.speed.mps();
      } 
    }
  }

Print the data

Again, in the loop() method include the printing methods.

//Printing
  char report[128];  
  memset(report, 0, sizeof(report));
  snprintf(report, sizeof(report), "%d, "
                                   "%4.2f, %4.2f, %4.2f, %4.2f, %4.2f, "
                                   "%8.7f, %8.7f, %4.2f, %4.2f, "
                                   "%4.2f", 
    treset, 
    ax, ay, az, t, p, 
    lat, lng, alt, speed,
    so2 );

  // Print the data to Serial
  Serial.println( report );

  // Save the data to SD card
  appendFile(filepath, report);
  appendFile(filepath, "\n");

  // Transmit the data via radio
  if (treset - tradio > 5000){
    tradio = millis();
    //sendData( report );
    Serial.println( "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA" );
  }
}