[SOLVED] Arduino JPEG over Serial

jonisykes

[SOLVED] Arduino JPEG over Serial

in Integration and Hardware • 7 months ago

Hi all,
I'm desperate for some help here, it seems I've tried everything.

What I'm trying to achieve:
I have an SD card on arduino, with a photo saved on it, for testing.
I'm trying to send that JPEG file through Serial, to processing, and save on my PC.
Sounds easy, except I also use the Serial port for the sending/receiving of commands and values for other methods.
So, what I've done is told Arduino to first send the file size, then tell processing that file transmission will begin, and send the file.
Once sending is complete I then send "EOF" to processing.

In processing, I'm using the serialEvent method to capture data from serial.
In the method I have a series of boolean "switches" controlled by if statements that parse the incoming data.
If it recongises that a photo will be transmitted, it then switches to "data input mode", and receives the data.
Every byte is parsed and is flagged if it is an 'E'.
If so, I then switch again to check for 'O' and 'F'. (This is me recognising the end of file).

Once the EOF has been detected, I then flush and close the output.

The problem:
No matter what method of storing bytes I try, the JPEG is never correct PC side.
I've tried storing each byte at a time,
saving them in a byte array and calling output.write on the whole array or trying saveBytes on the array too.

Here's my code:

void serialEvent(Serial myPort)
{
// read a byte from the serial port:
// myPort.readBytesUntil(',', byteBuffer);
//String inString = new String(byteBuffer);
String inString = null;
byte byteBuffer = 0;
byte tempByte = -1, tempByte2 = -1, tempByte3 = -1;

if(eFound && oFound && !fFound) // if e and o found, look for f.
{
    byteBuffer = (byte)myPort.read();
    tempByte3 = byteBuffer;
    println("3: " + tempByte3);
    if(tempByte3 == 70)
    {
      fFound = true;
      println("Found EOF");
    }
    else                                    //else not found, store original values in proper order.
    {
      append(photo, (byte)69);
      append(photo, (byte)79);
      append(photo, tempByte3);
      eFound = false;
      oFound = false;
      fFound = false;
    }
}
if(eFound && !oFound && !fFound) // if eFound, look here for 'O'
{
    byteBuffer = (byte)myPort.read();
    tempByte2 = byteBuffer;
    println("2: " + tempByte2);
    if(tempByte2 == 79)
    {
      oFound = true;
    }
    else
    {
      append(photo, (byte)69);
      append(photo, tempByte2);
      eFound = false;
      oFound = false;
      fFound = false;
    }
}
if(receivingPhoto && !eFound && !oFound && !fFound) //first bytes come in here.
{
    byteBuffer = (byte)myPort.read();
    tempByte = byteBuffer;
    println("1: " + tempByte);
    if(tempByte == 69)       // if 'E' is found, switch modes.
    {
      eFound = true;
    }
    else
    {
      eFound = false;
      oFound = false;
      fFound = false;
      append(photo, tempByte);
    }
}
else if(eFound && oFound && fFound && receivingPhoto) //if EOF store data.
{
    if(photo.length == photoSize)
    {
      saveBytes(filename, photo);
      //output.write(photo);
      //output.flush(); // Writes the remaining data to the file
      //output.close(); // Finishes the file
      eFound = false;
      oFound = false;
      fFound = false;
      receivingPhoto = false;
      println("Done!");
    }
    else
      println("Sizes don't match");
}
else if(!receivingPhoto)
    inString = myPort.readStringUntil(',');

// do other stuff with commands...

Replies(3)

knutl

Re: Arduino JPEG over Serial

7 months ago

I am not really familiar with the jpeg format, but I did a quick check with 3 of my jpeg files and they all contain a "eof" sequence....So check your jpeg and if you have a "eof" sequence somewhere, use something else to check for end -of file.

jonisykes

Re: Arduino JPEG over Serial

7 months ago

Hi, thanks for the quick reply,
This was one of the many things I've tried. EOI or EOF is dxFF dxd9 or something (can't remember off the top of my head)
in java. I tried searching for that too, it's essentially the same as what I have now.
The problem I'm having is no longer about finding the end of the file, its just not correctly writing bytes to it.

I can't see if that's due to a logical error, or I'm not using the right syntax, but I'm fairly sure that's where the problem is.

What frustrates me, is how there's an example for parsing serial input as strings, and a separate example for sending a jpeg over serial, but no one has thought of combining the two yet.

Again, any info on this is hugely appreciated.

Thanks, Joni

jonisykes

Re: Arduino JPEG over Serial

7 months ago

Always nice to answer your own question:

Code:
/////////////////////////////////////////////////////////////
void draw()
{
String inString = null;

if(readData)
{
    getPhoto();
}
else
{
    if( myPort.available() > 0 )
    {
      inString = myPort.readStringUntil(',');
    }
    if (inString != null)
    {
      println("Raw data: " + inString);
      // split the string into multiple strings
      // where there is a ":"
      String items[] = split(inString, ':');

      // if there was more than one string after the split
      if (items.length > 1)
      {
        // remove any whitespace from the label
        String label = trim(items[0]);
        // remove the ',' off the end
        String val = split(items[1], ',')[0];
        // check what the label was and update the appropriate variable
        if (label.equals("Ready"))
        {
          println(label);
        }
        else if (label.equals("Stopped"))
        {
          started = false;
          println(label);
        }
        else if (label.equals("Ping"))
        {
          if (val != null)
          {
            param = PApplet.parseInt(val);
            if (param >= 0)
            {
              drawLine = true;
              println("Index: " + pIndex);
              println("New ping: " + param + "\n");
            }
            else
            {
              noObstacle = true;
              drawLine = true;
              println("New ping: No obstacle detected");
            }
          }
        }
        else if (label.equals("Index"))
        {
          pIndex = PApplet.parseInt(val);
        }
        else if (label.equals("Clear"))
        {
          finished = true;
        }
        else if(label.equals("AIndex"))
        {
          aIndex = PApplet.parseInt(val);
        }
        else if (label.equals("Avg"))
        {
          avg = abs(PApplet.parseFloat(val));
          if(avg > 150)
            avg = 150;
          println("Av: " + avg);
          println("Index: " + (aIndex));
          showResult = true;
        }
        else if(label.equals("Size"))
        {
          photoSize = PApplet.parseInt(val);
          readData = true;
          myPort.clear();
          println("Photosize: " + photoSize);
          println("Beginning transmission...");
          myPort.write("send");
        }
      }//if value in message
    }//if not null
}//if not photo
}//draw

void keyPressed()
{
if(key == 27)
{
    key = 0;
    stop();
}
else if(key == ' ')
{
    myPort.write("size");
    println("Accessing file...");
}
else if(key == 'p')
{
    myPort.write("ping");
}
}//draw

void getPhoto()
{
byte[] buffer = new byte[64];
while(myPort.available() > 0)
{
    int readBytes = myPort.readBytes(buffer);
    print( "Reading ");
    print( readBytes );
    println( " bytes...");
    for(int i = 0; i < readBytes; i++)
    {
      photo = append(photo, buffer[i]);
    }
    println("Bytes received: " + photo.length);
    if(photoSize != 0 && photo.length == photoSize+3)
    {
      readData = false;
      myPort.clear();
      println("Received");
      savePhoto();
    }
}
}

void savePhoto()
{
print( "Writing ");
print(photo.length);
println( " bytes to disk...");
try
{
    output.write(photo);
    output.flush();
    output.close();
}
catch (IOException e)
{}
println( "DONE!");
}

void delay(int ms)
{
int time = millis();
while (millis () - time < ms);
}

void stop() //catch esc key and stop properly
{
println("Stopping...");
if (started)
    myPort.write("stop");
delay(200);
exit();
}

/////////////////////////////////////////////////////////////////

So despite my efforts, you can see that I had no choice but to move everything to the draw() loop in order to poll the serial port.

I managed to check the end of the JPEG file with my 'EOF' sent through from the board immediately after the file was sent, and checking for this in processing.

Bit of a hack, but it works.

If anyone wants help understanding any of this, feel free to message me and I'll do my best to help.

Joni

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