Recommend me a wireless module compatible with Axon II

[bilals]

May you please recommend a wireless module (i.e. Xbee) that is compatible with Axon II. I need one for my hexapod project.

Thanks in advance.

[waltr]

I'll guess you only need to send/receive a serial stream of data from your bot to a PC or point to point.
For that an XBee Series 1 running 802.15.4 works well.

Can you define your requirements?
Point to point or point to multi point?
Range?
Data speed?

[bilals]

Can you define your requirements?

I just want to be able to control the hexapod via PC wirelessly.

Point to point or point to multi point?

I don't know what your really mean. I am a NEWBIE !!!

Range?

about 10 meters radius

Data speed?

Does this include data from sensors , servos, etc... For now i am just going to use 18 servos in the hexapod. But i am willing to implement later many components (sensors, accelerometers...etc). So, i suggest a wireless module with enough data speed to handle as much data from components as possible.

[KurtEck]

I also use XBee version 1 with my Axon2 and it works fine.  It connects to either my PC or to a DIY remote control that I have mentioned in a few other threads.  From this remote I control my Axon2 Biped Brat.  I also use this controller to control a few other robots (Brat, Hex, Rover)that use microcontrollers from Basic Micro (Basic Atom Pros).

One issue I ran into with the XBEE on the Axon2 is I was having problems getting it to work with the sparkfun adapter board, but it works great with the board from selmaware. ...

Kurt

[waltr]

Yep, I know you are a newbe which is why I asked you questions. That is so you can think about what you want and how it may work.

Point to point means the there are only two wireless modules that only talk to each other. This is to differentiate from a multi-point in which there can be many sources or destinations for the data. You will see these terms when you read about wireless modules. Most of us use point to point for a robot.

For a hexapod control or any other robot you will need to invent a communication command protocol. Part of doing this is to decide how much direct control you wish to have of each motor (servo) in your bot. You could have this wireless link only cover high-level commands like "Go forward" or even "Go to the light", in which then the on board processor reads the sensors and controls each of the servos to accomplish the goal of the command.

Or you can do the wireless control at a lower level. The on board processor does the timing to the servos but the PC gives the commands to position each servo. This would require many more bits of data to be transferred to the bot. This would also require that all of the sensor readings taken by the on board processor be transferred to the PC.

Any data transferred between the bot and PC is in both directions and how often this data is needed counts to determine the data speed (baud rate) requirement. An XBee has a 250kbps rate on the RF link but can only do 115kbps max for real data and it is better to only consider 57.6kbps as the top data rate. Xbees like almost all wireless links are half-duplex, meaning they can only send data in one direction at a time. If you have a large amount of data in both directions then half the maximum rate for one direction, there is a small amount of time needed for an RF module to switch from transmitting to receiving. It also needs time to acknowledge reception of data or request a retransmission of the data.

When you do get to the point of writing code for the bot to communicate with your PC do this with a cable between them. Once this works replace the cable with the RF modules as it is easier to get one thing at a time working.

10 meters even through walls should be no problem for the low power XBees.

My latest robot has an XBee module to communicate with my PC. I only use it the send diagnostic data to the PC for analysis as the robot is totally autonomous. I do plan to use the RF link for high level status and commands in the future.

Does this help?

[bilals]

I also use XBee version 1 with my Axon2 and it works fine.

I was planning to buy Axon II and an Xbee module but wasn't sure they are compatible. Thanks for the Info.This helped

[bilals]

Does this help?

The explanation was great, thanks a lot. You seem to be a >>PRO<<   .

For a hexapod control or any other robot you will need to invent a communication command protocol. Part of doing this is to decide how much direct control you wish to have of each motor (servo) in your bot. You could have this wireless link only cover high-level commands like "Go forward" or even "Go to the light", in which then the on board processor reads the sensors and controls each of the servos to accomplish the goal of the command.

One thing i just want to make sure of is the high-level commands. You mean i'll write a whole program i.e. program that includes moving the robot forward/backward, turning, etc... (All movements of the servos to move the robot one step forward/backward, turn, etc..). I then will upload it to the Axon II (Where is it stored ?).
After that the high-level command will be for example "Go Forward" and it will trigger part of the program which is responsible for moving the robot one step forward.Is that right?

Do you think its better than low level commands ?

[GWER57]

You have to write routines like forwards and backwards that go on the axon and then your main routine gets data from your pc on what to do. so e.g. 1 = forwards 2= backwards 3= turn around, so to make the robot go your computer sends the data byte 1, the axon receives 1 and calls the forwards function which takes care of the low level stuff and moves your bot forwards. I hope that helps and you can also read admin's tutorial on uarts and bluetooth.(Not quite the same if you are using xbee but the same concept)

[bilals]

You have to write routines like forwards and backwards that go on the axon and then your main routine gets data from your pc on what to do. so e.g. 1 = forwards 2= backwards 3= turn around, so to make the robot go your computer sends the data byte 1, the axon receives 1 and calls the forwards function which takes care of the low level stuff and moves your bot forwards. I hope that helps and you can also read admin's tutorial on uarts and bluetooth.(Not quite the same if you are using xbee but the same concept)

Thanks, sure this helped.

[waltr]

It comes down to your choice on what a command will do in your bot.
I would start with a number of primitives, simple commands like "lift right-front leg", "move front-middle leg forward", "Turn head to +30degrees", "measure and report distance" then later combine these into a higher lever command like "go forward 1 meter then scan and report distance to all objects".
Putting all this together can be quite a challenge so start simple.

The explanation was great, thanks a lot. You seem to be a >>PRO<<

Uh..thanks, glad it helped.

From the link in your hexapod leg question I looked at he documents for the MSR-H01 pBrain HexEngine. There is a downloadable user manual for the commands to the HexEngine. This could be helpful to you to see what type of commands could be used and what their digital form could be.
The docs are here: http://www.hexapodrobot.com/products/electronics/p.Brain-HexEngine.html

[bilals]

I suddenly got confused regarding the Xbee module.

I am not really sure what i am talking about is it the Xbee Module/ Adapter Kit. Is the Xbee module or adapter kit the component that has to be connected to the MCU ? What do I need from the PC side to be able to communicate with the module/adapter? Is it a wireless card i.e. laptop built in wireless card or another xbee module/kit?

Can you please give me a link to the Xbee that I need to buy ?

This is totally different from Bluetooth, right ? Is the Bluetooth better to use ?

The docs are here: http://www.hexapodrobot.com/products/electronics/p.Brain-HexEngine.html[/url]

Thanks for the link

[KurtEck]

As for commands.  I have a set of pretty primitive commands that I use to talk between my Remote control and my robots, which I could describe in more details.  There is a thread talking about my conversion of the DIY remote control to XBEE based up on the Lynmotion website (http://www.lynxmotion.net/viewtopic.php?f=21&t=5447)

But basically the remote has:
    2 analog Joysticks
    2 analog sliders
   16 key keypad
    LCD display 2x16.

So my commands are more primitive.  That is I have a packet which contains the states of the controls (2 bytes for the buttons, 4 bytes for the joysticks, 2 bytes for the sliders).  My code is setup that instead of continuously blasting out the current values, it waits for the robot to ask for the current values.  It also has a mode that says tell me when something changes...

In addition to these messages I have some handshake stuff that says the remote is ready and use this ID to talk to me and likewise to say the remote is not ready.  Also I have a packet that the robot can send to the remote to say display this on the LCD...

The smarts on what to do with the different inputs is up to each robot. I currently have code in the remote that does a query to find out which XBEES are out there and I keep a list of them.  So I currently can press a key on the remote, scroll through my robots and choose the one I wish to play with now...  Again all pretty primitive.

As for which parts to order:
I would start off with the low power version 1s, with either a chip or wire antenna.
http://www.sparkfun.com/commerce/product_info.php?products_id=8664
or http://www.sparkfun.com/commerce/product_info.php?products_id=8665

Which?  Some say the chip ones don't have quite as far a range, but they work fine for me...

But now you need some way to connect it to the axon2.  One problem is the Xbees run at 3.3v and the Axon runs at 5v so you need come voltage conversion.  I use some of the sparkfun ones, but was having problems with it and the Axon so I use the appbee-sip from Selmaware (http://www.selmaware.com/appbee/index.htm).  They are much bigger and twice as expensive then the sparkfun one.  On the PC you can use the one from sparkfun: http://www.sparkfun.com/commerce/product_info.php?products_id=8687


Yes this is totally different than bluetooth,  which is better?  For me I like the XBEE as it gives me more flexibility.  I can control my robots from a VB app on my pc or from the remote.  Likewise each of these can easily talk to my different robots.  I am so in the process of probably converting my code from transparent mode to API mode.  What does this mean? instead of being a simple RS232 replacement, with a special configuration mode to change who I talk to (+++ atdl xxx...), you simply build a packet of data with the ID of who you wish to talk to.  Why I want to use this?  I may want my robot to talk to the remote control for commands and the like, but may also wish to send out diagnostic information to some program running on the pc.  But that is a whole other story.

I hope I did not confuse things.
Kurt

[waltr]

Nice summary Kurt and good interface boards to use for the XBees.

I also use the chip antenna on my bot and on the PC end I use the Digi USB XBIB board and an XBee with the SMA connector on which I have a rubber duck antenna. This, I'm sure help the range as the range is dependent on the antenna gain on both sides of the link.

 I am using the Sparkfun regulated explorer board but interface to a PIC and it works. I was in the discussion about this board and its use with an Axon a few months back. Either the Sparkfun or the AppleBee USB adapters should work fine.

The series 1 Xbees use the 802.15.4 protocol whereas Bluetooth uses the Bluetooth protocol. Both run at 2.4GHz but will not talk to each other. For short range robot control either should work equally as well. I believe XBee has a lower data rate but Bluetooth a shorter range.

The XBees I'm using are the Series 2 running the full ZigBee protocall so the Robot is actually part of my ZigBee network. This is a bit trickier to get working than just two Series 1 modules in a point to point transparent setup but fits in with my other PAN needs.

[bilals]

Thank you guys for the help, i hope i am not bothering you with my questions. I have some more, so please be patient.

Just to make sure i get it correctly.What you are saying  KurtEck is that I need:
*2 XBees 1mW Wire Antenna (one for the microcontroller and one for the PC)
*AppBee-SIP (Is it the AppBee-SIP or AppBee-SIP-LV ?), this is for the microcontroller side
*XBee Explorer USB, for the PC side.


Now 1 Xbee will be connected to the AppBee-SIP, the ApeeBee will then be connected to the microcontroller.
So, how do you connect the Xbee to the AppBee (Is it by soldering or you just attach it?). And how do you connect the AppBee to AxonII.


The second Xbee will be connected to the Xbee Explorer USB and to PC via USB cable.

So, is this right ? I hope soooooooooooooooooo.  

An edit to the reply:

Lets forget about the above for a minute,is this this what i need:
http://www.trossenrobotics.com/p/Xbee-Communication-Starter-Kit.aspx

Is the XBee Explorer Regulated (See the link above) compatible with AxonII

[KurtEck]

No problem.

As for the Trossen starter kit.  That pretty well shows everything I mentioned in the previous post except that I substituted the Appbee-sip for the Sparkfun the XBee Explorer Regulated.  The sparkfun has worked fine on my Basic Atom Pro setups, but did not work for me with the Axon2.  There was 1 or 2 other threads on this at the same time where some speculated that voltage conversion circuits using leds/diodes and the like was not getting the low voltage low enough for the Axon so since I had some of the Selmaware ones, I tried it and it worked... I don't know if anyone else has tried again with the Sparkfun ones and had success.

Here is a picture of the Appbee-sip:

The XBees plug into the adapter boards.  The connectors are shown in the upper part of the above picture.

You use a USB cable to connect to your PC. 

To connect the Appbee-Sip or Sparkfun Explorer regulated, you will need to wire up a cable.  In the Appbee, it already had a 6 pin connector soldered in, of which you probably only need 4.  I used two two wire cables (one red/black) which I plugged into the power pins and connected the other end to some power pins on the Axon2 and the Green/Yellow cable I plugged into RX/TX and then plugged into one of the UARTS RX/TX pins... With the Sparkfun it is similar except it did not have any connector pins soldered in.  On some I added the pins on others I simply soldered the wires to the board... 

Hope that helps.

Kurt

[bilals]

Thanks KurtEck, it was a thorough explanation. I think i will try my luck with Trossen kit as it will be easier for me buying the AxonII and the Trossen starter Kit online as I live in middle east (The two items will be shipped together). I hope the sparksfun explorer regulated works fine. If not then cant help it, i'll order an Appbee-SIP.

[waltr]

Look up the threads on the Sparkfun regulated explorer board and the Axon. Also do look at the schematic for the Sparkfun regulated explorer board to see how they protect the XBee's DIN from overvoltage using a series diode.

If you can solder small SM components then this protection circuit can be changed so that it will work with the Axon. When you get the parts and start working with them start a thread here (or continue the XBee-Axon thread) for modifications.

[bilals]

If you can solder small SM components then this protection circuit can be changed so that it will work with the Axon. When you get the parts and start working with them start a thread here (or continue the XBee-Axon thread) for modifications.

Thanks waltr

I sure will seek your help once i get the components.

Thanks again

[waltr]

Just found this on interfacing the XBee's DIN to a 5V processor so wanted to get the link posted before I lose it.
http://forums.trossenrobotics.com/tutorials/how-to-diy-128/xbee-basics-3259/