How to write data to a text file on Arduino

Question

I have some position data continually coming in and I am currently printing it to the serial.

Say I have the string "5" and want to print that to a text file, "myTextFile", what would I need to do to achieve this? To be clear, the text file would be saved on my computer not on an SD card on the Arduino.

Also, is their a way to create a text file within the program before I start saving to it?

So you have some SD card connected to the Arduino and you want to create and write file onto it? — KIIV, Nov 08 '16 at 07:16
I want to write the file onto the computer that the arduino is connected to. Going to make that more clear in question now, thanks. — Michael Zakariaie, Nov 08 '16 at 07:23
You can use Putty, to connect Arduino and configure it to write output. Otherwise your own computer side software is required. — KIIV, Nov 08 '16 at 07:32

score 5 · Answer 1 · edited Dec 25 '18 at 10:26

You can create a python script to read the serial port and write the results into a text file:

##############
## Script listens to serial port and writes contents into a file
##############
## requires pySerial to be installed 
import serial  # sudo pip install pyserial should work

serial_port = '/dev/ttyACM0';
baud_rate = 9600; #In arduino, Serial.begin(baud_rate)
write_to_file_path = "output.txt";

output_file = open(write_to_file_path, "w+");
ser = serial.Serial(serial_port, baud_rate)
while True:
    line = ser.readline();
    line = line.decode("utf-8") #ser.readline returns a binary, convert to string
    print(line);
    output_file.write(line);

perfect answer. just had to change `serial_port` to mine on mac `/dev/cu.usb____` — khaverim, Dec 25 '18 at 01:25

score 0 · Answer 2 · answered Nov 08 '16 at 10:20

U have to Use serial-lib for this

Serial.begin(9600);

Write your sensor values to the serial interface using

Serial.println(value);

in your loop method

on the processing side use a PrintWriter to write the data read from the serial port to a file

import processing.serial.*;
Serial mySerial;
PrintWriter output;
void setup() {
   mySerial = new Serial( this, Serial.list()[0], 9600 );
   output = createWriter( "data.txt" );
}
void draw() {
    if (mySerial.available() > 0 ) {
         String value = mySerial.readString();
         if ( value != null ) {
              output.println( value );
         }
    }
}

void keyPressed() {
    output.flush();  // Writes the remaining data to the file
    output.close();  // Finishes the file
    exit();  // Stops the program
}

This is the answer I am after however it is very unclear. Can anybody clarify how to set this up and explain what is happening in these functions? — Steve, Jan 18 '18 at 02:00

How to write data to a text file on Arduino

2 Answers2

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