Oops… the Supply Voltage on my motion sensor is already down to 3060 millivolts. Suddenly it’s dropping very fast; this sensor has been operational for more then 7 weeks now, with IIRC 2 new and 1 older rechargeable battery of a brand with which i’ve had bad experiences before. I hope that’s what is causing this, cause if not, i have some work to do
The other 2 battery powered sensors are still doing fine, BTW:
Supply Voltages (click to view the realtime values)
I updated my ZigBee network webpage and added a configuration panel with which i can configure all the XBee radios in my WSN (well, it’s a WSAN actually).
XBee config
Since my Home Automation system doesn’t have a GUI of itself and configuring XBee radios from a touchscreen without keyboard didn’t sound like a good idea either, i thought it would be best to create a web page for that. There’s still some work to be done in showing the XBee response on the page after the remote AT command has executed, but that’s a minor thing; “under water” i can see everything is working fine. With a click of the ‘Send’ button the values entered on the page are concatenated into a single string with a special delimiter and then sent off to my system using XMLRPC. The ZigBee API interface will then construct 1 or more ZigBee frames based on the values, send those frames to the targeted XBee radio(s) and wait for the responses to arrive. That’s it, basically.
Being able to do all this, is what makes me feel i’m getting somewhere; now that i’m able to monitor and configure my XBee radios in a convenient way, it’s time to really move on and start ‘mass production’ of all kinds of sensors and other stuff that are on my wish list.. starting with a bunch of motion detectors and a LED strip controller! After that, some room-oriented sensors (combining motion, temperature, light and perhaps humidity in one package) will be made. Can’t wait!
With an increasing amount of XBee modules operational (6, at the time i write this) and the nature of a ZigBee network, i felt the need to monitor some network related stuff; what’s going on in there?? Do my End Devices make use of a Router when i relocate them, further away from the Coordinator? What about signal strength? All those questions can be answered with the ZigBee Network monitor i created last weekend.
It’s totally integrated into my Domotica system of course, which takes care of 95% of all the work; what was left was parsing the Remote AT Command responses coming back from the XBees. For example, a response byte of 33 to the ‘DB’ command means that the RSSI of the last received packet is -51 dBm. Task scheduler, database storage, events being triggered on value changes, it’s all available. Want to create a chart of RSSI values? Easy. Receive SMS alert when a XBee is ‘lost’? Consider it done.
I created a webpage that shows the current values for some XBee configuration values, produced by this ZigBee Network monitor. No more X-CTU for me (OK, not completely: uploading the right firmware and changing some initial settings will still be done from behind the PC…) But once the right PAN ID has been set and the XBee has joined, local configuration isn’t needed anymore. This makes life a lot easier!
For those not really experienced in recognizing XBee API frames from a byte stream: there’s not a single valid frame to be found inside all those bytes. But this is what my Coordinator received today.
But that’s OK; i intentionally left the XBee running on low batteries; I wanted to see what would happen. My code that should recognize valid XBee API packets just got it’s ultimate real life test. Cause normally, the byte stream coming from the Zigbee Coordinator is so clean you can hardly test it without writing a special tool that creates a mix of garbage, valid and invalid frames. Now i know for sure my code works!
Another good thing i saw, is that this ‘dying’ XBee didn’t create that much traffic resulting in other XBee’s not being able to get their messages to the Coordinator anymore.
This is really important actually; imagine you’re on holiday and a sensor runs out of battery power; do you really want to monitor your Home Automation system for that kind of trouble while you’re at the other side of the world? Become a slave of your own system? And have to call your neighbor that feeds the cat to remove the batteries or worse ? (“I don’t care how you do it, just do it.. Cut some red wires if you have to!”) Just to keep the system running? Not me!
In the meantime, this really nice weather only makes you want to play outside; sitting behind a computer with an airco blowing cold air in your neck is not my favorite right now:
Here are the results of the test i started 3 days ago. After 3 days of monitoring the XBee supply voltage the alkaline batteries were empty and with a bit of tweaking i got the data out of the logs and into an Excel sheet so i could create a chart:
XBee Supply Voltage
OK, this looks good and it’s easy to do; all you need are some changed settings on the XBee, a Domotica system that can fire the ‘IS’ remote AT Command to your XBee and your done. Well, almost
The JeeNode has been running a small sketch that transmits a dummy string every 5 seconds; without any sleeping and also keeping the XBee on all the time:
#include <NewSoftSerial.h>
#define SERDBG 1
NewSoftSerial XBSerial = NewSoftSerial(2, 3);
int CTSpin = 7;
int XBpin = 6;
static void Send () {
// send a dummy string
XBSerial.print(millis());
XBSerial.print(" ");
XBSerial.println("XBeeaaaaaa");
#if SERDBG
Serial.print(millis());
Serial.print(" ");
Serial.println("XBeeaaaaaa");
#endif
}
void setup() {
// setup XBee
pinMode(CTSpin,INPUT);
pinMode(XBpin,OUTPUT);
digitalWrite(XBpin,LOW);
digitalWrite(CTSpin,LOW);
delay(10);
XBSerial.begin(9600);
#if SERDBG
Serial.begin(9600);
#endif
// give XBee some time to join PAN
delay(5000);
// let the world know we're here
XBSerial.println("[XBeeVoltage]");
#if SERDBG
Serial.println("[XBeeVoltage]");
#endif
}
void loop() {
delay(5000);
Send();
}
The JeeNode stopped working at around 2/3 of the horizontal axis, so after 48 hours or so where the voltage had already dropped to 2,64 V. The XBee is still working as i write this, with a voltage of 2,3 V. I wonder how long it takes for the XBee to give up too…
Conclusion: this can definitely be used as a way to remotely monitor my battery powered sensors; Yippee!
One thing i would really like, is being able to monitor the voltage the JeeNode and XBee are running on. Now the XBee has a %V command, specially for reading the voltage on the Vcc pin. So let’s see of i can use this.
The first thing i noticed was that the XBee i configured with the AT End Device firmware, didn’t respond to the %V command. Hmm, correct; the manual was very clear about it: the %V command is only supported by a Router and not by a Coordinator or an End Device. And it’s those End Devices (which will run on batteries) that i want to monitor…
OK.. next command to have a look at was the ‘IS‘ command, which stands for Force Sample; this command forces a read of all enabled digital and analog input lines and a small comment told me it could also return the supply voltage: “Analog samples are ordered sequentially from AD0/DIO0 to AD3/DIO3, to the supply voltage.” So lets try this one, shouldn’t be to hard i guess?
So i added support for this command to my API and started sending frames to the XBee:
I won’t go into detail of every byte in the frame above, but the 2 bytes marked in red are the ASCII codes for ‘I’ and ‘S’: yes, ‘IS’, the command we want to be executed on the remote XBee. The response that came back from the XBee was encouraging, however, no supply voltage was present, only the values of some random Analog input lines i enabled:
With the help of an example i found out the meaning of the Command data:
IS response example
OK… the frames that were being received looked nice, but it’s not what i want… where’s the supply voltage? The example above doesn’t show it either.. but it must be possible, right?
After searching for more than an hour, i suddenly bumped upon a setting in the X-CTU tool (in the I/O Sampling section), that had the following description:
Configure the supply voltage high threshold. If the supply voltage measurement equals or drops below this threshold, the supply voltage will be included in an IO sample transmission. RANGE:0-0XFFFF
Aahh, that must be it… this setting has a default of 0, causing the supply voltage to never be included in an IO sample! I set the value to FFFF, disabled all other I/O lines on the XBee et voila:
This means there is 1 sample set, containing the supply voltage, and the value is: 0ABC.
Multiply this with 1200/1024 and you get the supply voltage in mV:
($0ABC =) 2748 * 1200/1024 = 3220 mV. Great!
Tomorrow i’ll add some code to my HA system to periodically send an IS command to this XBee and store the results. And then just wait and see what happens when i let a JeeNode and XBee running on alkaline batteries 24/7…
After my problems with the MS13 sensors yesterday, i managed to find some spare time (even though, or maybe because it was father’s day) to write a sketch for the new motion sensor i created during the last couple of weeks. Always taking one step at a time, i located the first prototype of this sensor at a place where i can see the enclosure LED from the living room: i want to know how it performs…
New motion sensor
Now powered by 3 rechargable NiCd batteries and with all hardware nicely put away in the enclosure. In due time the enclosure will be moved out of sight so only the PIR will be visible. I’ve decided to use 3.5 mm jack plugs to be able to disconnect the enclosure from the sensor, so i can easily take the enclosure back to my office, because i don’t think the JeeNode is already running the final version of the ‘PIR’ sketch…
A new class, 2 database records and 1 line of code were enough to get the sensor working in my Domotica system:
procedure TAMN31112.ProcessInterfaceData;
begin
Pin(1).AsBoolean:= (O.Data[1]='1');
end;
The new PIR can be viewed from my website (it’s called BP PIR):
Battery powered PIR
The sketch is still under development; for instance, how much difference would it make if i change the DigitalRead() into a bitRead()? I’ll have to read more about that on JeeLabs … Other questions are: should i increase the heartbeat interval (currently 45 seconds) or the Motion report interval? Can i create some sort of battery power monitoring with the XBee? But that will all be investigated when i’ve finished building my second motion sensor based on JeeNode and XBee..
The enclosure i used this time is a bit different from the enclosure i used on a previous occasion. This one lacks the inner ribs and opening and closing is a bit harder: for opening the enclosure you need to put a screwdriver between the 2 halves and twist it to get the enclosure open. The first thing i did was making my life easier by removing the ribs that keep the 2 halves together on one side of the enclosure. Some more modifications here and there now make it possible to open the enclosure without any additional tools, but still will not open by accident.
I drilled a 10 mm hole into the PIR enclosure so that the PIR fitted nicely through the top plate; a drop of super glue on the inside did the rest. There was plenty of room for the 100k pull-down resistor inside the PIR enclosure so i soldered it to the PIR there. An extra hole of 4 mm and a cable tie for the wire completed the PIR box.
JeeNode, XBee
This being my first motion sensor built this way, i added a LED to be able to see what the XBee radio is doing; is it still transmitting or not, when, how often, etc. ? Maybe this is overkill, but when this sensor is placed somewhere in the house with no computer screen nearby, it can be very handy to see if the sensor is still functioning instead of running to and from the nearest screen…
If the flickering of the LED is to visible or annoying in the future, i can always disable it or make it invisible by a piece of tape over it; but for now, this LED seemed like a good idea to have. The LED lights up when the XBee is on and from the duration that the LED stays on i can see what’s happening; whether it’s transmitting (very short durations) or having PAN trouble (long).
The software part of this sensor will be the most time consuming of it all i guess. Since i want it to be battery powered, i’ll have to consider what is relevant information for my Domotica system, and when it is. In fact, the only thing that really matters is one single thing: fast motion detection! All the rest is less important.
Cause what do we Domoticans use this motion detection for? To turn things ON… not OFF; at least, i don’t.
Further more, a quick look in my events history tells me that from 01-04-2010 till today i missed (my 433 MHz RFXCOM receivers, i mean) a total 869 ‘OFF’ transmissions (meaning “no motion”) from my 10 MS13 motion detectors. That’s way to much to be called reliable! So my system already has the capability to deal with this situation of missing ‘OFF’ transmissions; when a MS13 hasn’t reported neither an ‘ON’ nor an ‘OFF’ for a specific time interval, i set the motion sensor back to ‘OFF’ in software.
So.. i could as well do without this ‘OFF’ completely; i don’t use it as a trigger, so why send this non-information anyway?
What i do want to have is a heartbeat, every 90 seconds or so. And i would like to have an ‘ON’ being sent with a specific interval when motion is detected continuously. That’s what I’ll be working on in the coming week.
Now that my Zigbee/Jeenode equipped pressure sensor is working for 3 months without any problems, it was time to leave the breadboard stage and move on to something more permanent. While ordering new Jeenodes at Jean-Claude Wipplers shop, i stumbled upon a post (i should read his daily weblog more often!) that showed me just what i needed: an enclosure that looked just right for this job. I ordered the Jeenodes, 2 enclosures (1 extra for when i mess up the first one and don’t want to wait for a second delivery..) and some other handy stuff.
First i sawed off the part of the PCB that i didn’t need, to decrease it’s size.
JeeNode PCB size reduction
Guess what? Now the length of the PCB equals the internal width of the enclosure! Nice… I still had some battery holders laying around that also fitted quite well:
Enclosure, batt holder and JeeNode
I didn’t want to leave off the FTDI headers, so i used 6 straight headers and removed the plastic strip from the headers after the headers were soldered onto the PCB. With the plastic headers left on, the completed PCB was just a bit to wide for the enclosure, which caused tension and the enclosure wouldn’t close well anymore.
Next item that had to be prepared, was the XBee Breakout Board. Normally the top of this Breakout Board contains the 2mm XBee headers and the 0.1″ spaced headers are at the opposite side. I removed the bottom headers i soldered in when i used this board for other purposes and soldered 6 wires on it from the top, only for those pins i really needed:
XBee Breakout Board
Pin 1 (labeled Vcc) for Power, Pin 3 (labeled DIN) for transmission, Pin 9 (DTR) for controlling Sleep mode, Pin 10 (GND), Pin 11(CTS) and Pin 12 (ON) for the LED. This makes the Breakout board a lot thinner and the wires are coming out between the board and the XBee module.
After soldering the wires coming from the XBee board to the JeeNode, drilling a hole for the LED (which blinks when a pressure sample is being sent), soldering the wires and gluing the battery holder into the enclosure, it looked like this:
Almost done!
The FTDI headers are very handy now, for uploading the sketch with the JeeNode already inside the enclosure; cause all you have to do is open the enclosure, gently lift up the left side of the JeeNode and connect the cable. So whenever i need to upgrade the JeeNode, i don’t have to worry about connecting issues.
FTDI cable connected to the JeeNode
Now all there was left to do was moving the XBee module and the Pressure Plug from the Breadboard to their new ‘home’, add 4 batteries, click on the other half of the enclosure and.. my first WAF certified sensor was born!
Today i had some spare time to combine a few of the things i’ve been working on lately:
My Zigbee API;
Arduino;
Pan & Tilt mechanism
I wanted to create a small executable that would enable me to control the position of the 2 servo’s.
XBee module
I started with programming the XBee: Zigbee End Device AT firmware, the right PAN, Node Identifier ED5 (as in End Device 5), Sleep Mode=1 (Pin Hibernate). I put the module on a breadboard by use of a Breakout Board. Grounded pin 9 and used the 3.3V output of the Arduino to power the module.
Arduino
I strapped the Arduino Duemilanove to the same breadboard and wired the 2 servo’s. Pins 9 and 10 of the Arduino are used as PWM output for the 2 servo’s. Arduino pins 2 & 3 were connected to the DIN and DOUT pins of the XBee module.
Sketch
Now it was time to write a sketch that would receive commands from the XBee and move the servo’s accordingly. The sketch is a real quick and dirty one, low on error handling and validation. I made up a small ‘protocol’: commands have to end with the exclamation mark (“!”) and can be either 1 or 2 characters long.
P+! would Pan right 3 degrees, P-! would Pan left 3 degrees, T+! would Tilt up 3 degrees and so on. H! is the command to go back to the Home position. Of course you can extend this as much as you like, e.g. add absolute positioning, presets, you name it.
This is the sketch:
#include <NewSoftSerial.h>
#include <ServoTimer1.h>
#include <PString.h>
ServoTimer1 PanServo;
ServoTimer1 TiltServo;
int PanAngle = 90;
int TiltAngle = 90;
byte DeltaPan = 3; // move 3 degrees
byte DeltaTilt = 3; // move 3 degrees
char cbuffer[40] = ""; // receive buffer
NewSoftSerial XBSerial = NewSoftSerial(2, 3);
PString buffer(cbuffer, sizeof(cbuffer));
void setup() {
XBSerial.begin(9600); // set up XBee at 9600 bps
delay(10000); // wait 10 sec. for possible joining
PanServo.attach(9);
TiltServo.attach(10);
PanServo.write(PanAngle);
TiltServo.write(TiltAngle);
}
void waitforcommand()
{
while (true)
{
if (XBSerial.available())
{
int c = XBSerial.read();
if (c == 0x21) // command terminator = "!"
{
break;
}
else
{
// add to buffer
buffer.print(c,BYTE);
};
};
};
}
void loop() {
buffer="";
waitforcommand();
// what's the first character?
switch (buffer[0])
{
case 0x50: // P for Pan
{
// what's the next character?
switch (buffer[1])
{
case 0x2B: // +
PanAngle += DeltaPan;
break;
case 0x2D: // -
PanAngle -= DeltaPan;
break;
};
break;
};
case 0x54: // T for Tilt
{
// what's the next character?
switch (buffer[1])
{
case 0x2B: // +
TiltAngle += DeltaTilt;
break;
case 0x2D: // -
TiltAngle -= DeltaTilt;
break;
};
break;
};
case 0x48: // H for Home
{
PanAngle=90;
TiltAngle=90;
break;
};
};
// check boundaries for Pan
PanAngle=(PanAngle < 0)?0:PanAngle;
PanAngle=(PanAngle > 180)?180:PanAngle;
// check boundaries for Tilt
TiltAngle=(TiltAngle < 90)?90:TiltAngle;
TiltAngle=(TiltAngle > 180)?180:TiltAngle;
// Set dervo's accordingly
PanServo.write(PanAngle);
TiltServo.write(TiltAngle);
}
PC software
Next item was a small program that would use the API to address the XBee module.
XBee servo control
4 buttons for Left, Rigth, Up and Down, a Home button and a button to connect to the Zigbee network. Not very spectacular, I’d say.
There are 2 important API functions that are used to communicate with the Zigbee module:
Node Discovery
XBee Transmit Request.
The code that is executed when the “Connect” button is pressed, sends out a Node Discovery command. This will trigger all joined Zigbee modules to respond with information about themselves, like 16- and 64-bit address, node identifier and some more interesting stuff. The code goes something like this:
The Node Identifier is used to see if the Zigbee module that is connected to the Arduino, is “in the air”. Cause it doesn’t have to be, it could be disconnected from power or whatever…
When the Zigbee module with Node Identifier “”ED5″ has responded, the 5 buttons are enabled and clicking them will move the servo’s. This is done with the XBee Transmit Request function; a string is being sent to the XBee and the XBee will take care of transferring it out on the UART. Below the code for the “Home” button:
i:=gXBeeModules.Indexof('ED5');
if i >=0
then begin
The enclosure i used this time is a bit different from the enclosure i used on a 
