Really Nice Gauges

Recently I was shown an extremely nice set of gauges by a fellow on the Arduino forum, graynomad.  They were metalic looking and had a great set of parameters to mess with.  Well, I couldn't resist, and decided to figure out how to use them and somehow get them on this site.

Well, I sort of got it working.  It seems that Google (Blogger) has a problem with iframes, and that's pretty much the only way to include one of these.  The problem is that it messes with the scrollbar in Chrome, their own browser.  I'm not sure how they show up in IE, except they won't show up at all in IE8 because it doesn't support canvas.  For something this complex, the canvas is the only practical solution short of using something like Flash.

So, if you're using Chrome, look over to the right where the scrollbar is, notice it doesn't look right?  If you put your mouse over there and click, you'll see that it actually works, but just doesn't look right.  I don't have a solution to this yet.

But, let's look at the gauge.  Notice it has an LCD display and a moving hand.  When my energy usage goes above the red indicator (it's on the dial), the little red LED will light up.  These are all parameters that can be set for the gauge.  I chose the brass look simply because it fit my taste, there are many, many combinations possible.  The gauge is sort of real time.  What I do is update it every 10 seconds from my datastore at Cosm which is updated every 60 seconds.  So, every minute or so, it will be updated to reflect the current power usage at my house.  I plan on working with these gauges quite a bit more; they're just too nice to leave alone.

So, if you want to use them also, or just admire the tremendous amount of work that went into creating them, they're known as the SteelSeries and apparently were initially designed for weather displays.  Just go to Google and start looking.  If I gave a URL, it would be the wrong one or outdated or something, so check it out yourself.

And, sorry about your scrollbar; it'll come back when you go leave this page.

Let's Talk About Septic Tanks

Nice subject....right?  Since I live out in the sticks, there are no services here except power and phone.  I have my own well, propane tanks, and septic system.  Since it's a relatively new septic system, it has all the new and improved features.  This usually means there is more to worry about and take care of, and at least in my case, this is certainly true.

My first problem came a few years ago when sewage backed up into the house.  Since I had only a general idea where the tank was actually located, the service guy had to hunt a while to find the access ports on the tank.  See, newer septic tanks have two access points for different stages of sewage treatment and both of them have to be pumped out.  When he uncovered it, I found out I had a filter inside the tank.

Yes, there is a filter that stops solids from making their way out into the leach field.  The filter had plugged up and was not releasing fluid into the leach field.  That filled the tank and caused me to have a mess in the bathroom.  Nice.  So, obviously, the tank filter needed to be cleaned and the tank pumped out to restore service.  So, I had the service company install risers with nice green covers on them to allow (relatively) easy access to the septic tank so I could clean the filter.  Total bill, around $800.  Not something I wanted to repeat very often.  Here's a picture that illustrates the kind of thing I'm talking about:

All you see at ground level is the green plastic covers.  Just remove these to service the tank.  Here is what the filter looks like:

To clean it, just grab the blue handle, pull the filter out, and bang it around.  Once you knock the debris off, rinsing it is easy, just spray it down with a water hose.  Here is the basic configuration of the tank and the various parts inside:

Except I have a riser on both sides so each tank can be easily pumped out.  Notice the 'sanitary tee' on the inlet side?  That causes problems as well; more on that below.

Fast forward a year.  I had company with kids and the darn tank filled up again.  I opened the wonderful new access points, and sure enough, the tank was full again.  Called the same service company and they came out and cleaned it out for me again.  I chose this solution to get the house working again since I had company at the house that needed to use the bathroom.  Total bill, $340.

A couple of weeks ago, it happened again.  This time I didn't have company, so I went out and cleaned the filter.  The tank immediately started to drain into the leach field and drop the level, and by the next day, it was back to a normal level.  No costs, this is the way to do it.  However, about four days later the house backed up again.  When I opened the access point, the tank was at the proper level, and the filter was clean.  What the heck was up with that?

Seems when the tank was full, a clot of toilet paper formed on the inlet side and had turned to concrete.  See, what happens is that the 'sanitary tee' caught all the toilet paper and allowed a plug to form on the inlet.  When I lowered the level of the tank, the plug hardened and I had a new problem to deal with.  I spent most of the day with a water hose and jet nozzle breaking up the plug and restoring septic service to the house.  This needs some solution that doesn't require me to remember that the darn filter needs to be cleaned, and a way of clearing the pipes that doesn't entail a days work with a water hose.

So, I bought one of these:

This is a hose and special jet that you hook to your power washer and run through the sewer system to clear out clogs.  It won't work on tree roots or cave ins, but it will clear most clogs quite nicely.  Since I had never used one before, I was skeptical, but it did a great job.  It pulls itself along breaking up stuff and washing it down the sewer line.  If it stops at a bend or a clog, just pull it back a little bit and let it go; it will work its way through the clog and around the corner after a couple of tries.  Really nice tool.  Total time to clean out the pipes was around 30 minutes and most of that was figuring out how to hook the device up to the power washer.

But, to prevent the problem from sneaking up on me and flooding the bathroom was still a problem.  With a little searching I found out that there were floats that are specifically designed to tell you when the septic level rises.  I got one of these:

This is a normally closed float switch.  I chose normally closed so that I would know that the level was OK by a closure and it would open when the level got too high.  This way I knew the switch was OK and wouldn't have to wait for the sewer to back up to find out the switch was broken.

Total cost for both items: $150 including shipping.  I consider this a wise investment since now I can tell if the tank is rising and clean the filter long before it backs up into the house.  I also have a way of clearing the pipe easily each time I open up the tank to prevent the toilet-paper-turned-to-concrete-plug problem.  Sure, I could just clean the filter every six months or so, but who remembers that kind of thing?  Especially since this is probably the nastiest job one can take on around the house.  'Sanitary tee' ?  Who the heck thought of that name?

I haven't hooked the float into the house network yet, but that will come over the next month or so.  That's a problem that I already know how to deal with.  I plan on having a little light come on somewhere inside the house that I can't ignore; heck, I may have it send me email also.

I have the coolest septic tank in the area.

Alternatives to Cosm (Pachube), Part 2

(edited heavily on Dec 11, look below to see why)
Previously <link> I discussed the possible use of Sen.se as an alternative to Cosm.  This is becoming important to me because Cosm seems to be slowing down over time.  The users on their forum have brought this to the developers attention and there have been responses, but I'm having trouble loading a single day of data without a server error and failure to display the data.  So, I just tried out another offering emoncms.org.  It's pretty darn compelling.

The problem with most of the services that I've investigated though is there just isn't enough documentation on what it does, how it does it, where it stores the data, etc.  This is somewhat true of emoncms, but at least there's enough (including its forum) to actually use it.  It took me most of an afternoon to prowl through enough documentation and user comments to get it working.  The part that held me up the most was finding out how to get my data to the service.  It turns out that it's relatively easy to have an Arduino send the data to the service and then construct graphs and things using emoncms tools.

However, there are a number of odd problems relating to embedding their graphs into a blog page.  When I first put this page up I had a multigraph and a gauge that showed real time usage.  The problem was that using the scripts turned off the scroll bar for the page.  That's a bit unacceptable, so I edited the page to remove the visual display.  There are also a few display problems when using their dashboard, but it mostly works.  Here's the link to my dashboard with gauges and graphs that indicate real time data <link>.

Like I said, this is a very compelling site.  One problem may be that this site is open source and maintained by a community of interested users.  That means that it will grow quickly and capabilities will be added as they are thought of and users make the changes (unfortunately, it's the same for bugs).  That makes it somewhat unpredictable.

I can deal with that.

Like I said though, it's a bit tough to find out how to send data from an Arduino to the site.  I got it to work with minimal trouble after searching a lot on the site and its forum.  Here's a code snippet to illustrate how to do it:

The Arduino Sketch

void sendEmoncmsData(){
  char dataBuf[100];

  if(emoncms.connected()) // already trying to get data, just leave
    return;
  // construct the data buffer so we know how long it is
  strcpy_P(Dbuf2, PSTR("{RealPower:%d, PowerFactor:0.%d, PowerVoltage:%d.%02d, PowerFrequency:%d.%02d, InsideTemp:%d, OutsideTemp:%d}"));
  sprintf(dataBuf,Dbuf2,
    (int)round(realPower),
    (int)(powerFactor*100),
    (int)rmsVoltage,
    (int)(((rmsVoltage+0.005) - (int)rmsVoltage) * 100),
    (int)(frequency),
    (int)(((frequency+0.005) - (int)frequency) * 100),
    (ThermoData[0].currentTemp + ThermoData[1].currentTemp)/2,
    (int)round(outsideSensor.temp));
    Serial.println(dataBuf); // take this out when you've got it working
//    return;  // so you can see the buffer before you actually send it
  strcpy_P(Dbuf,PSTR("emoncms Connecting..."));
  Serial.print(Dbuf);
  if(emoncms.connect()){ // set a limit on how long the connect will wait
    strcpy_P(Dbuf,PSTR("OK..."));
    Serial.print(Dbuf);
    tNow = now();
    strcpy_P(Dbuf,PSTR("GET http://emoncms.org/input/post?apikey=secretnumbers &json="));
    emoncms.write(Dbuf);
    emoncms.write(dataBuf);
    emoncms.write("\n");
    emoncms.stop();
  }
  else {
    strcpy_P(Dbuf,PSTR("failed..."));
    Serial.print(Dbuf);
    emoncms.stop();
    while(emoncms.status() != 0){
      delay(5);
    }
  }
}

See, it's a simple json interaction that names the variable that you want to save data for.  emoncms will create the data store and name it for you.  All maintenance for the data can be done from their site.

This could well become my new cloud storage for data.

Battery Charging - Part 5 (Harbor Freight item 42292)

Yes, I finally assembled and tested the various ideas into a single box for my float charger for lead acid batteries.  This project has been going on for over a year now and may be getting close to having a nice working prototype.  I incorporated a voltage display and an XBee set up to transmit analog readings into the mix.  So, what happens is you plug the charger into the wall and the XBee comes on, samples the voltage before the output diode and sends it to whatever device you set it up to talk to.  This way I can monitor the battery state of charge remotely without even having to go into the garage.  Here's an interior view of the charger:

On the lower left is the charging circuit that I came up with based (roughly) on the Harbor Freight 42292; at the top, stuck to the side is a series 2 XBee plugged into a breakout board; and on the right is the voltmeter display.  This is all enclosed in a plastic rectangular enclosure.  When assembled it looks like this:

Of course, since the XBee is a 3.3V device, I had to add a power supply for it.  I took the power directly from the float voltage and used an AP1117T33 regulator.  When I first started testing the combination, it got pretty hot pretty quickly, even when it wasn't hooked to a battery.  A little checking (I unplugged the XBee) told me that the XBee and its two LEDs were sucking enough power to heat it up, so I enabled sleep on the XBee.  This way, it would be off most of the time and only turn on to take a couple of measurements and transmit them.  This totally solved the problem.Here's the schematic I eventually settled on.  

If you're following this, you'll see that it's a simple variable supply that I set to 13.4V with resistor R2 which feeds a 3.3V supply to power the XBee.  The voltage divider R4, R5 sets the level that is in the 1.2V analog input range of the XBee.  Since these regulators sometimes tend to oscillate, I added capacitors C1 and C2 just to make sure I didn't drive the XBee nuts.  That's also why I added the resistor R6, to keep it away from reset.

To set it up, I put a 1K resistor across the output and set the voltage using R2 to 13.4 volts.  Then I centered the pot R5 and checked what was being transmitted.  By adjusting the pot, I was able to get a nice reading at the receiving end which I translated back into voltage and can display with an XBee connected Arduino.

There's a little jitter in the XBee readings caused by transients.  I can solve that two ways, add a capacitor on pin 20 of the XBee or do a rolling average on the receiving device.  I haven't decided which to do yet. I'm leaning toward a rolling average, but experience will tell me if it even needs to be fixed.  Here's a short sample of the Arduino output I set up.  Obviously, this isn't what I'll eventually use, but it's nice to be able to see the charger out in the garage:

A fun item I noticed is that the circuitry for monitoring the battery and transmitting the value can be separated from the charger.  That way I could hook a device to the battery and it would transmit the voltage to something that could alert me to go attend to the darn thing.  I may pursue that for something in the future.

No, I'm still not done.  This thing was a real pain to build.  It came up from several prototypes and kept getting more complex and looks like a mess because of this.  I think I may journey into getting a custom PC board made to put the thing together with since I want at least five of them.  Also, since I now have a box that will hold it, I'm going to mount the components on the lid with a wire to the display on the box part.  That way I can actually screw stuff down so it doesn't bounce around over time.

Apple Device: "Charging is not supported with this accessory"

I don't have a single Apple device in my house, no iPad, iPhone, iPod, iAnything.  I don't even have any apples.  However, the little wall warts I bought <link> have a bad reputation because they don't work on some iDevices.  While it's true that they don't, it really isn't their fault, it's Apple's.  This is the message:

Notice that it doesn't say that the device is the wrong voltage, wrong polarity, or wrong anything else?  That's because the device just doesn't meet the Apple standards of being made by Apple specifically for a particular Apple device.  They really, really want to lock you into buying your stuff from them and them alone.

My little chargers are fine and will work with Apple stuff with a simple modification that I won't do since I don't need to charge Apple devices.  What Apple did was use the D- and D+ (the two middle pins on a standard type A usb plug) to supply specific voltages that Apple could look at to tell if the charger was one of theirs.

Well, this little trick didn't last long before the engineers that make battery extenders and chargers figured it out.  Obviously, they grabbed a real apple charger and ripped it open to see what kind of shenanigans Apple was up to.  One manufacturer Lady Ada wrote up a nice description of what was happening and how she worked around it for one of her products, the MintyBoost.  She has a nice description of how she overcame the problem and made her stuff work <link>.

This also explains over 90% of the complaints on the web about various iDevices not working with a charger.  Basically, these two voltages (D1 and D2) are tiny and can vary a lot based on contact resistance, length of cable, net draw of the device, etc.  Basically any darn thing at all.  For example some of the solutions are to turn off the iPhone, plug the cable and charger into the phone, plug the charger into the wall, turn on the phone, repeat a number of times to allow the gremlins to align correctly.  And, this occasionally works.  Another solution is to lower the screen intensity, put the phone in airplane mode, then hook up the charger. There's always someone that says you need a new cable, better charger, or hold your mouth differently.  In the case of the iPhone, there was an OS update that caused a significant number people to have charging problems.  The fix for many of these non-technical folk was to go to the Apple store and get a new device or have a new part installed that will work.  Of course there are the Apple cultist that insist that only a new Apple charger will solve the problem.

But people, electrons are electrons and it isn't you or your device when a problem like this turns up, it's Apple exercising their control over their cult.  Annoying.

Don't despair yet.  There are ways to get around this problem that actually make sense.  No, you don't need to wet a Qtip with perfume and clean the contacts, letting it air dry for an hour(this is a real suggestion), there are much more mundane solutions.  For example, this site <link> talks about a little connector that has Apple plugs on both ends and works around the problem.  However, the darn thing is too expensive (I'm not a fan of this solution, but some of you might be).  There are several other similar devices out there that solve the problem.  You can also solve the problem by building something yourself (gasp !); I know this goes against life philosophy of the myriad teenagers that talked their parents into getting this cool new gadget, but life isn't fair.

Just cut a USB charging cable that mates with the device and add a little voltage divider.  The schematic of the changes is:

If this picture doesn't look familiar, take another look at Lady Ada's description, it was taken directly from there.  See, Apple uses the voltage divider to set specific voltages on D+ and D- to identify their devices.  Other manufacturers don't do this kind of thing unless they're trying to meet the USB charging standards, and for a low price device it isn't worth the effort or cost. Just another effort of Apple to wrangle you into their pen.

So, you ask, "What do you care, you don't own an Apple device?"  I don't, but my less fortunate friends, neighbors, and relatives do.  They get really annoyed when their devices won't work on one of my chargers when they come to visit, and they hate it when a charger stops working and gives them this silly, non descriptive message.  Also, I found zero, nada, explanations of what was going on to help people with this problem.  That annoyed me more than anything else, so I decided to post it here and a couple of other places, hoping that poor souls that are eating up Google cpu cycles could, at least, understand the problem better.

Soak a Qtip in perfume and clean the contacts?  Really?

Tiny Power Supplies for Micro Controller Projects

When you build micro controller projects, eventually you want to do something real that will have to work long term.  For this you need a power supply that is small, maybe small enough to put in a light switch, ceiling fan, or dryer control panel.  These things are hard to find.  I've spent hours on Google trying to find really small 5V supplies with some success, but never fitting my needs.  Nice little supplies that you have to buy in 100+ quantities, nice little supplies that cost US $50, etc are out there, but who wants to invest that kind of money in a technology that changes almost daily?

In a few project postings I describe how I cut the guts out of a wall wart like this:

These little devices work great as microcontroller power supplies.  The one above will put out up to 2A and doesn't seem to get hot doing it.  I've had several in service, out in the weather for two years.  At a cost less than US $5 each (usually with free shipping) they are a fine solution.  I've taken the supply out of the plastic case and installed it into devices like this <link>:

The little board in the upper left is the guts of the wall wart.  I've even used the entire wall wart as a mounting platform for another device:

This device <link> has an XBee mounted on the side of the wall wart transmitting temperature every minute or so.  All-in-all, a pretty useful device repurposed from the iPad craze.  However, technology moves on and I want to try a couple of ideas that would work better if I had an even smaller power supply.  I asked on a couple of forums and was pointed to one of these:

I already had two of them charging mobile devices in the house so I decided to gut one of them and see what was inside:

This little supply is TINY. Yes, I had to cut the case off with a Dremel to get to the guts; the top was seriously glued to the bottom and refused to come off. The two board with connecting cable configuration could create a problem mounting, but nothing I can't overcome, and the wires to the AC pins might give me a problem, but it couldn't be too hard to solve; I like this.  So, looking around the web to see what kind of deal I could get on them I found them for US $1 on Amazon.  Yes, you read that right, a single dollar, with free shipping.  So:

Here's my pile of stock devices.  

Since supply and demand act on everything, the price at Amazon has gone up to US $1.45 as of this writing and could go either up or down based on activity, but they are still a bargain.  

Even with this solution available, I'm still searching for possibilities.  The rough requirements for the supply are: minuscule size, 5V at a least an amp (relays, you know), easy to mount, things like that.  

To you suppliers out there, there's a market here that you aren't exploiting.  SparkFun, Lady Ada, Itead, etc. are you listening?  You folks in China, what are you waiting for?

Using the XBee Library Part 2

Previously, I talked about using Andrew Rapp's XBee library on a project and posted an example.  This is the second example I've been working on.  The objective is to understand the library well enough to re-implement some of my devices using the library because I'm getting tired of doing my own parsing of the basic packet.  Yes, I have finer control, but I've found I don't really need finer control.  So, here is an example of using the code on an Arduino 2560 with the XBee connected to Serial3.  This leaves me two unused serial ports to play with since I'm using the main serial port as my debugging and status port.

The Arduino Sketch

/*
XBee RX test for a Arduino Mega2560 using Serial3 as the XBee serial
input for a Series 2 XBee.  I took Andrew Rapp's receive example and modified
it heavily.

I wanted to experiment with and better understand how to use his XBee
library for an actual project.  With the inclusion of support for SoftwareSerial
so that the XBee can be put on digital pins leaving the Arduino serial port
available for debugging and status, the library's usefullness shot way up.  These
changes also allow for the use of the additional serial ports on a Mega2560

This is a HEAVILY commented example of how to grab a receive packet off the
air and do something with it using series 2 XBees.  This example also supports
a remote XBee end device sending analog data.  Series 1 XBees are left as an
exercise for the student.
*/

#include <XBee.h>

XBee xbee = XBee();
XBeeResponse response = XBeeResponse();
// create reusable response objects for responses we expect to handle
ZBRxResponse rx = ZBRxResponse();
ZBRxIoSampleResponse ioSample = ZBRxIoSampleResponse();

void setup() {
  // start serial
  Serial.begin(9600);
  // and the third serial port
  Serial3.begin(9600);
  // now that they are started, hook the XBee into
  // the third serial port
  xbee.setSerial(Serial3);
  // I think this is the only line actually left over
  // from Andrew's original example
  Serial.println("starting up yo!");
}

void loop() {
    // doing the read without a timer makes it non-blocking, so
    // you can do other stuff in loop() as well.
    xbee.readPacket();
    // so the read above will set the available up to
    // work when you check it.
    if (xbee.getResponse().isAvailable()) {
      // got something
      // I commented out the printing of the entire frame, but
      // left the code in place in case you want to see it for
      // debugging or something.  The actual code is down below.
      //showFrameData();
      Serial.print("Frame Type is ");
      // Andrew calls the frame type ApiId, it's the first byte
      // of the frame specific data in the packet.
      Serial.println(xbee.getResponse().getApiId(), HEX);
   
      if (xbee.getResponse().getApiId() == ZB_RX_RESPONSE) {
        // got a zb rx packet, the kind this code is looking for
     
        // now that you know it's a receive packet
        // fill in the values
        xbee.getResponse().getZBRxResponse(rx);
     
        // this is how you get the 64 bit address out of
        // the incoming packet so you know which device
        // it came from
        Serial.print("Got an rx packet from: ");
        XBeeAddress64 senderLongAddress = rx.getRemoteAddress64();
        print32Bits(senderLongAddress.getMsb());
        Serial.print(" ");
        print32Bits(senderLongAddress.getLsb());
     
        // this is how to get the sender's
        // 16 bit address and show it
        uint16_t senderShortAddress = rx.getRemoteAddress16();
        Serial.print(" (");
        print16Bits(senderShortAddress);
        Serial.println(")");
     
        // The option byte is a bit field
        if (rx.getOption() & ZB_PACKET_ACKNOWLEDGED)
            // the sender got an ACK
          Serial.println("packet acknowledged");
        if (rx.getOption() & ZB_BROADCAST_PACKET)
          // This was a broadcast packet
          Serial.println("broadcast Packet");
       
        Serial.print("checksum is ");
        Serial.println(rx.getChecksum(), HEX);
     
        // this is the packet length
        Serial.print("packet length is ");
        Serial.print(rx.getPacketLength(), DEC);
     
        // this is the payload length, probably
        // what you actually want to use
        Serial.print(", data payload length is ");
        Serial.println(rx.getDataLength(),DEC);
     
        // this is the actual data you sent
        Serial.println("Received Data: ");
        for (int i = 0; i < rx.getDataLength(); i++) {
          print8Bits(rx.getData()[i]);
          Serial.print(' ');
        }
     
        // and an ascii representation for those of us
        // that send text through the XBee
        Serial.println();
        for (int i= 0; i < rx.getDataLength(); i++){
          Serial.write(' ');
          if (iscntrl(rx.getData()[i]))
            Serial.write(' ');
          else
            Serial.write(rx.getData()[i]);
          Serial.write(' ');
        }
        Serial.println();
        // So, for example, you could do something like this:
        handleXbeeRxMessage(rx.getData(), rx.getDataLength());
        Serial.println();
      }
      else if (xbee.getResponse().getApiId() == ZB_IO_SAMPLE_RESPONSE) {
        xbee.getResponse().getZBRxIoSampleResponse(ioSample);
        Serial.print("Received I/O Sample from: ");
        // this is how you get the 64 bit address out of
        // the incoming packet so you know which device
        // it came from
        XBeeAddress64 senderLongAddress = ioSample.getRemoteAddress64();
        print32Bits(senderLongAddress.getMsb());
        Serial.print(" ");
        print32Bits(senderLongAddress.getLsb());
     
        // this is how to get the sender's
        // 16 bit address and show it
        // However, end devices that have sleep enabled
        // will change this value each time they wake up.
        uint16_t senderShortAddress = ioSample.getRemoteAddress16();
        Serial.print(" (");
        print16Bits(senderShortAddress);
        Serial.println(")");
        // Now, we have to deal with the data pins on the
        // remote XBee
        if (ioSample.containsAnalog()) {
          Serial.println("Sample contains analog data");
          // the bitmask shows which XBee pins are returning
          // analog data (see XBee documentation for description)
            uint8_t bitmask = ioSample.getAnalogMask();
            for (uint8_t x = 0; x < 8; x++){
            if ((bitmask & (1 << x)) != 0){
              Serial.print("position ");
              Serial.print(x, DEC);
              Serial.print(" value: ");
              Serial.print(ioSample.getAnalog(x));
              Serial.println();
            }
          }
        }
        // Now, we'll deal with the digital pins
        if (ioSample.containsDigital()) {
          Serial.println("Sample contains digtal data");
          // this bitmask is longer (16 bits) and you have to
          // retrieve it as Msb, Lsb and assemble it to get the
          // relevant pins.
          uint16_t bitmask = ioSample.getDigitalMaskMsb();
          bitmask <<= 8;  //shift the Msb into the proper position
          // and in the Lsb to give a 16 bit mask of pins
          // (once again see the Digi documentation for definition
          bitmask |= ioSample.getDigitalMaskLsb();
          // this loop is just like the one above, but covers all
          // 16 bits of the digital mask word.  Remember though,
          // not all the positions correspond to a pin on the XBee
          for (uint8_t x = 0; x < 16; x++){
            if ((bitmask & (1 << x)) != 0){
              Serial.print("position ");
              Serial.print(x, DEC);
              Serial.print(" value: ");
              // isDigitalOn takes values from 0-15
              // and returns an On-Off (high-low).
              Serial.print(ioSample.isDigitalOn(x), DEC);
              Serial.println();
            }
          }
        }
        Serial.println();
      }

      else {
        Serial.print("Got frame id: ");
        Serial.println(xbee.getResponse().getApiId(), HEX);
      }
    }
    else if (xbee.getResponse().isError()) {
      // some kind of error happened, I put the stars in so
      // it could easily be found
      Serial.print("************************************* error code:");
      Serial.println(xbee.getResponse().getErrorCode(),DEC);
    }
    else {
      // I hate else statements that don't have some kind
      // ending.  This is where you handle other things
    }
}

void handleXbeeRxMessage(uint8_t *data, uint8_t length){
  // this is just a stub to show how to get the data,
  // and is where you put your code to do something with
  // it.
  for (int i = 0; i < length; i++){
//    Serial.print(data[i]);
  }
//  Serial.println();
}

void showFrameData(){
  Serial.println("Incoming frame data:");
  for (int i = 0; i < xbee.getResponse().getFrameDataLength(); i++) {
    print8Bits(xbee.getResponse().getFrameData()[i]);
    Serial.print(' ');
  }
  Serial.println();
  for (int i= 0; i < xbee.getResponse().getFrameDataLength(); i++){
    Serial.write(' ');
    if (iscntrl(xbee.getResponse().getFrameData()[i]))
      Serial.write(' ');
    else
      Serial.write(xbee.getResponse().getFrameData()[i]);
    Serial.write(' ');
  }
  Serial.println();
}

// these routines are just to print the data with
// leading zeros and allow formatting such that it
// will be easy to read.
void print32Bits(uint32_t dw){
  print16Bits(dw >> 16);
  print16Bits(dw & 0xFFFF);
}

void print16Bits(uint16_t w){
  print8Bits(w >> 8);
  print8Bits(w & 0x00FF);
}

void print8Bits(byte c){
  uint8_t nibble = (c >> 4);
  if (nibble <= 9)
    Serial.write(nibble + 0x30);
  else
    Serial.write(nibble + 0x37);
     
  nibble = (uint8_t) (c & 0x0F);
  if (nibble <= 9)
    Serial.write(nibble + 0x30);
  else
    Serial.write(nibble + 0x37);
}

It was actually pretty easy to convert my previous example to the 2560; I just changed the port in setSerial() to Serial3 instead of newsoftserial and it worked.  This left me a little time to play with capturing an I/O packet and taking it apart.  The code to handle an I/O packet is in this example.

I wanted the I/O packet because I have an XBee outside on a pole measuring the temperature that sends I/O packets periodically and I want to set up a battery monitor for my lead acid batteries to keep track of their state of charge.  You don't need an Arduino hooked to an XBee for these purposes, but you do need to be able to receive and decode the packets.

Once again, feel free to grab the code and modify it for your purposes.