Send String from Processing to Arduino

Question

I have been working on a project with my Arduino Mega 2560 and WS2812B addressable LED lights. The Arduino IDE code determines the colour of each LED based on the letter in the corresponding string of characters e.g. "ABACBABABCABAB". This is used to light up 254 LEDs and works as expected.

The trouble I am having is with the next step of being able to create a GUI that allows for a user to select a pattern from a list of 100s and for the Arduino to pick up on that new string of characters to change the LED pattern.

I am using the serial port to send this string to Arduino and when I enter a pattern into the Serial Monitor it works great. However, I am having trouble on communicating this string to the serial port using Processing.

The plan is to use processing to create a GUI that allows users to simply select the pattern and for it to send the string to the Serial Port. I am stuck at why this isn't sending and can't troubleshoot because I can't open the serial monitor on Arduino and send the string from Processing at the same time.

Here is the Arduino code:

#include <FastLED.h>
#define NUM_LEDS 50
// Data pin that led data will be written out over
#define DATA_PIN 6
#define BRIGHTNESS  32
CRGB leds[NUM_LEDS];
const byte numChars = 200;
char receivedChars[numChars];

boolean newData = false;

void setup() {
    Serial.begin(9600);
    Serial.println("<Arduino is ready>");
    FastLED.addLeds<WS2812B, DATA_PIN, GRB>(leds, NUM_LEDS);
    FastLED.setBrightness(BRIGHTNESS);

}

void loop() {
    recvWithStartEndMarkers();
    showNewData();
}

void recvWithStartEndMarkers() {
    static boolean recvInProgress = false;
    static byte ndx = 0;
    char startMarker = '<';
    char endMarker = '>';
    char rc;

    while (Serial.available() > 0 && newData == false) {
        rc = Serial.read();

        if (recvInProgress == true) {
            if (rc != endMarker) {
                receivedChars[ndx] = rc;
                ndx++;
                if (ndx >= numChars) {
                    ndx = numChars - 1;
                }
            }
            else {
                receivedChars[ndx] = '\0'; // terminate the string
                recvInProgress = false;
                ndx = 0;
                newData = true;
            }
        }

        else if (rc == startMarker) {
            recvInProgress = true;
        }
    }
}

void showNewData() {
    if (newData == true) {
        Serial.print("This just in ... ");
        Serial.println(receivedChars);
    String   str = receivedChars;
     for(int whiteLed = 0; whiteLed < NUM_LEDS; whiteLed = whiteLed + 1) {
      // Turn our current led on to white, then show the leds
      if (str.charAt(whiteLed) == 'A') {
      leds[whiteLed] = CRGB::Green;
      }
      if (str.charAt(whiteLed) == 'B') {
      leds[whiteLed] = CRGB::Blue;
      }
      if (str.charAt(whiteLed) == 'C') {
      leds[whiteLed] = CRGB::Yellow;
      }
      if (str.charAt(whiteLed) == 'D') {
      leds[whiteLed] = CRGB::Pink;
      }
      if (str.charAt(whiteLed) == 'E') {
      leds[whiteLed] = CRGB::Orange;
      }
      if (str.charAt(whiteLed) == 'F') {
      leds[whiteLed] = CRGB::White;
      }
      if (str.charAt(whiteLed) == 'G') {
      leds[whiteLed] = CRGB::Red;
      }
      if (str.charAt(whiteLed) == 'H') {
      leds[whiteLed] = CRGB::Brown;
      }
      if (str.charAt(whiteLed) == 'X') {
      leds[whiteLed] = CRGB::Black;
      }
      }
      // Show the leds (only one of which is set to white, from above)
      FastLED.show();

        newData = false;
    }
}

Here is the simple processing code

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

void setup() {

  String portName = Serial.list()[0]; //change the 0 to a 1 or 2 etc. to match your port
   myPort = new Serial(this, portName, 9600);       //initialize the serial port object
}

void draw() {                    //this is like the 'loop' section of code on Arduino



String pattern = "<AAABBBABCCCAAABCCCCBAAAABCCCCCAAAABBB>";
   myPort.write(pattern);

}

Any help is much appreciated, I am new to all of this so apologies for any mistakes.

D

Gius Gius · Accepted Answer · 2020-01-03T10:21:47

Check first if with this simple tutorial you can get the communication. Then compare your code with the tutorial code.

Send String from Processing to Arduino

1 Answers