Good practice for sending data from Arduino to Processing

Processing Electronics (Arduino, etc.)
5

update

example v02 
// https://discourse.processing.org/t/good-practice-for-sending-data-from-arduino-to-processing/6339/2

// on arduino make and send a JSON String,

// in processing catch the line and use
// https://processing.org/reference/parseJSONObject_.html
// https://processing.org/reference/JSONObject.html

// add to Array and save to file:
// https://processing.org/reference/saveJSONArray_.html
//_________________________________________________________
// test on WIN7 32bit
// and processing IDE 3.4

import processing.serial.*;
Serial myPort;  // Create object from Serial class

String inString = "{ \"UNO_1\" : { \"A0\" : 1000 , \"A1\" : 1001, \"A2\" : 1002, \"A3\" : 1003, \"A4\" : 1004, \"A5\" : 1005 } }";
String outfilename = "data/arduinocatch.json";
// String outfilename = "/run/shm/arduinocatch.json";  // for RPI
//______
JSONArray  allArduinoLines = new JSONArray();
JSONObject arduinoLine     = new JSONObject();
JSONObject values          = new JSONObject();   // to catch just the value list ( of the inner {  } ) 
String remoteIOdevice = "UNO_1";
String[] channels = {"A0","A1","A2","A3","A4","A5"};
int bdrate = 115200;

//_________________________________________________________
void setup() {
  size(200,200);
  get_line();  // init
  printArray(Serial.list());
  String portName = Serial.list()[1];               // here it was "COM3"
  myPort = new Serial(this, portName, bdrate);
}

//_________________________________________________________
void get_line() {
  arduinoLine =  parseJSONObject(inString);
  println(" new inString: "+arduinoLine);
  allArduinoLines.append(arduinoLine);
}

//_________________________________________________________
void to_file() {
  saveJSONArray(allArduinoLines, outfilename);
}

//_________________________________________________________
void draw() {
  background(200,200,0);
  check_serial();
  show_line();
}

void check_serial() {
  while (myPort.available() > 0) {
    inString = myPort.readString();
    println("serial event: "+inString);
    if (inString != null) {
      get_line();
      to_file();
  }
 }
}

//_________________________________________________________
void show_line() {  // take JSON object "arduinoLine" appart and show as text
  int dpos=20, ypos =  dpos;                       // canvas text layout
  values = arduinoLine.getJSONObject(remoteIOdevice);
  //println(" data from: "+remoteIOdevice+" \n"+values);
  fill(0);
  text(remoteIOdevice            , dpos, ypos); ypos += dpos;
  for (int i = 0;i<6;i++) text(channels[i]+": "+values.getInt(channels[i]), 2*dpos, ypos +i*dpos);
}

//_________________________________________________________
/*
first time started: dir and file is created
/data/arduinocatch.json
content:
[{"UNO_1": {
  "A1": 1001,
  "A2": 1002,
  "A3": 1003,
  "A0": 1000
}}]

*/


/*    Arduino code used here:

// test on Arduino Leonardo USB to win7 PC found "COM3"
// to send a JSON like full text record
String JSON;
int channels[6];

void setup() {
  Serial.begin(115200);
  while (!Serial) { ; }  // wait for serial port to connect. Needed for LEONARDO..
}

void get_Ain() {
  for (int i=0;i<6;i++)   channels[i] = analogRead(i);
}

void makeJSON() {
 JSON = "{ \"UNO_1\" : { ";
 for (int i=0;i<6;i++)  {
  JSON += " \"A";
  JSON += i;
  JSON += "\" : ";
  JSON += channels[i];
  if ( i < 5 )JSON += " , ";  
 }
  JSON += " } } ";
}

void loop() {
  get_Ain();
  makeJSON();
  Serial.println(JSON);   // to processing
  delay(1000);
}

*/

@matheplica what hardware you have to test this?
update: i checked on Raspberry Pi 3B+
and there it was on

/dev/ttyACM0 (Arduino Leonardo )

and i recommend to change data storage from uSDcard to (temporary) RAM DISK
( because write every second to card wears it out in?? )

String outfilename = “/run/shm/arduinocatch.json”; // for RPI

//___________________

@rodrigogamboa i did notice in your arduino code

delay(1); // delay in between reads for stability

pls, that is one millisecond ( not one second )
so possibly you are up to high speed sampling,
then i would recommend a total different way.

  • -a- you sample to array as fast as possible
    ( add there is special speedy code if you sample one channel only )
  • -b- in a batch type communication you send that whole array to processing
  • -c- you build a oscilloscope like view

i play this on processing, python or webserver

35kHz on one channel for Arduino and 520kHz for MAX32.

check out my BLOG and search for PoorManScope

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