Arduino Accelerometer Output Processing to CSV File - csv

Question

I am trying to convert ADXL335 accelerometer data from arduino to a csv file. The arduino code works perfectly when looking at it using the serial monitor. The processing code returns an output in the console but does not write anything into the CSV file. I'm not sure why it won't print. When I uncomment the print in the second if statement, the values are stored in the csv file, but it only works for 15 value inputs and then repeats these same values until the code is stopped. When we embed the if statements, we again get nothing in the csv file. I think there is something with the first if statement but I am not sure how to continue troubleshooting. I'm wondering how I can make it so I get a continuous output of the accelerometer readings. Thanks in advance.
Here is my arduino code:
void setup() {
pinMode(14,INPUT);//define mode of pin
pinMode(15,INPUT);
pinMode(16,INPUT);
Serial.begin(9600);//serial communication begin
delay(10);
}
void loop()
{
//Serial.print(",");
Serial.print("X=");
Serial.print(analogRead(14));
Serial.print(",");
Serial.print("Y=");
Serial.print(analogRead(15));
Serial.print(",");
Serial.print("Z=");
Serial.print(analogRead(16));
Serial.println(",");
delay(100);
}
Here is my processing code:
void setup() {
output = createWriter( "data.csv" );
mySerial = new Serial( this, Serial.list()[1], 9600 );
}
void draw() {
if (mySerial.available() > 0 ) {
value = mySerial.readString();
System.out.print(value);
output.println(value);
}
if ( value != null ) {
//output.println(value);
output.println();
}
}
void keyPressed() {
output.flush(); // Writes the remaining data to the file
output.close(); // Finishes the file
exit(); // Stops the program
}

Answer 1

First off you might want to change your arduino code to output valid CSV lines.
I'd suggest loosing the CSV header for now, or appending it from Processing.
Try this for now:
void loop()
{
Serial.print(analogRead(14));
Serial.print(",");
Serial.print(analogRead(15));
Serial.print(",");
Serial.print(analogRead(16));
Serial.println(",");
delay(100);
}
This should output something like ####,####,####, which is a valid CSV line.
On the processing side I would also advise first buffering until the new line(\n) character, which you can easily do with bufferUntil() and serialEvent()
import processing.serial.*;
// serial port
Serial mySerial;
// single line containing acc. values as a CSV row string
String values;
// the output
PrintWriter output;
void setup() {
output = createWriter( "data.csv" );
try{
mySerial = new Serial( this, Serial.list()[1], 9600 );
mySerial.bufferUntil('\n');
}catch(Exception e){
println("Error opening serial port: double check USB cable, if Serial Monitor is open, etc.");
e.printStackTrace();
}
}
void draw() {
background(0);
if(values != null){
text("most recent values:\n" + values,10,15);
}
}
// gets called when new data is in, and since we're buffering until \n it's one csv line at a time
void serialEvent(Serial p) {
values = p.readString();
if(values != null && values.length() > 0){
println(values);
// if values.trim() isn't call, the \n should still be there so print() will suffice in terms of adding a new line
output.print(values);
}else{
println("received invalid serial data");
}
}
void keyPressed() {
output.flush(); // Writes the remaining data to the file
output.close(); // Finishes the file
exit(); // Stops the program
}
Also notice error checking on the serial connection and serial data read
(it's a good habit checking for things that could go wrong).
Optionally you can add a header to your CSV file in setup():
output = createWriter( "data.csv" );
output.println("X,Y,Z,");
In terms of writing a CSV file there are many ways to do that and Processing has a Table class which allows you to read/parse and write CSV data. At the moment your PrintWriter approach is pretty straight forward: use that.