USB interface crashes after about one hour

I'm working on code to sense environmental data from a remote location using XBees, my Mac MIni, Processing, and XCode. I run my Processing code on the Mac. The Mac is connected via USB to the coordinator XBee, which in turn communicates wirelessly to the remote end-item XBee. Remote data is parsed by the Processing code and stored on the Mac's disk drive as a .dat file. The XCode Objective-C program reads that .dat file asynchronously, examines the data and sends an SMS message to my iPhone if something is amiss at the remote location.

I have all the parts working great. You can see a block diagram here: block_diagram

There is, however, one problem. The Processing and Obj-C programs loop continuously, checking the remote data about every 20 seconds. After about one hour, though, the Processing code breaks down. It no longer speaks to the coordinator XBee. I believe it has something to do with the USB interface. If I halt the Processing code, quit Processing altogether and disconnect/reconnect the USB cable, and then reload/rerun the Processing code, I can get the system working again. But for the life of me I can't figure out what is causing the problem after running fine for an hour or so.

Here are what I think are the pertinent lines of my Processing code:

    import processing.serial.*;

      Serial port;                     // Create object from Serial class

      byte[] dataArray = new byte [40];  //create an array for the data read from the remote xbee
      byte[] dataArray3 = new byte [40]; //create an array for the date read from the coordinator (xbee3)
      byte[] shopData = new byte [32];   //create an array for the shop data stored to disk
      byte chksum;
      int count = 0;
      byte  doorstatus;
      byte  htrctrl;
      int   lightlevel;
      float temp1;
      float temp2;
      int temp3;
      float degreesC;
      float degreesF;
      byte  pumpctrl;
      float   pumppressure;
      int delayval = 100;  // 100 ms

      int i = 0;                       // array index
      int x;                           // scratch value
      float y;                         // scratch value

      //set up addresses for each xbee in the network
      int xbee1addrlow = 0x40B098E6;  //end unit 1
      int xbee2addrlow = 0x40ACC07E;  //end unit 2
      int xbee3addrlow = 0x4089DF59;  //coordinator unit

      void setup() {
        String arduinoPort = Serial.list()[5];
        port = new Serial(this, arduinoPort, 9600);

The complete Processing code file is here.

The complete Objective-C code file is here. Though I don't think the issue is at all related to the C code. The same problem occurs whether I run the C code or not.

Sorry about this long post. If anyone has any ideas, I'd be very grateful.


Kevin H.

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