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trying to transfer data from Arduino to my Mac Mini (using Processing)

kjhart0133

Hello all,

 

I'm trying to transfer data generated on an Arduino Uno R3 to a file on my Mac Mini.  I'm using Processing on the Mac and the Mac is connected to the Arduino via the USB cable.  I'm also using two slightly modified sketches I lifted from the Arduino and Processing stock examples.  Basically, Arduino is reading a value on Analog Input 0 from a potentiometer and sending that out to the Serial port.  I've set the pot at an arbitrary position.

 

The attached file shows a screenshot from my Mac with five windows:

 

1.  The Arduino sketch

2.  The Processing sketch

3.  The Arduino Serial Monitor window showing the data being sent from the Arduino to the Mac.  In this case it is a constant value from the potentiometer setting.

4.  A hexdump of the file where the data is written to by the Processing sketch, and

5.  The bottom of the Processing window showing the data that is read over the Serial bus by the port.read statement in the Processing sketch

 

This screenshot can also be viewed at: http://www.flickr.com/photos/kjhart0133/8350131108/sizes/o/in/photostream/ with a little better resolution

 

Somewhere in the data transfer something odd is happening to the numbers.  What is being sent by Arduino is not what is being read by Processing (note the position of the println() statement in the Processing sketch.) I've spent a lot of time trying to figure out what's going on here, but alas I'm stymied.  Can anyone see what I'm missing?

 

Any help is appreciated.

 

Thanks,

 

Kevin H.

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    Well, I'm going to answer my own question here because I finally figured it out.  And, as it is in most of these programming problems, it was a very simple mistake.  I had used Serial.println() in the Arduino sketch to send the data out over the serial bus.  I should have used Serial.write() instead.  That's all it took; now the data transfer is working perfectly.

     

    I don't yet know what the difference is between Serial.println() and Serial.write() but apparently Serial.write() sends the raw data in byte format whereas Serial.println() probably formats it in ASCII for the display, or something like that.

     

    Thank you and good night.


    Kevin H.