Author Topic: XBee  (Read 10586 times)

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Offline CornelamTopic starter

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XBee
« on: October 07, 2008, 05:26:13 AM »
I want to use XBee-Pro to send and receive data from my computer to the robot and from the robot to the computer but is Xbee two-way? I mean i want to send commands to the robot (left,right etc) and receive images from the robot' camera. Can it be done using only 2 Xbee's? One on the computer and one on the Robot???
Thanks in advance!

Offline izua

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Re: XBee
« Reply #1 on: October 07, 2008, 05:56:47 AM »
You won't be able to send a video stream via xbee (speed is pretty low, IIRC).
However, you might be able to send other stuff (monitor sensors, send commands, download the firmware, etc).

I'm interested in a more technical approach for this too - as in, what would I need, what kind of output do the zigbee devices have, etc.
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline dunk

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Re: XBee
« Reply #2 on: October 07, 2008, 06:21:37 AM »
the Xbee-PRO has a fairly high transmission rate.
Quote
RF data rate: 250 Kbps

according to http://www.digi.com/products/wireless/point-multipoint/xbee-pro-series1-modulespecs.jsp
it's worth noting that this speed is half duplex though. ie. you can only send at that speed in one direction at a time.

so while on paper the Xbee might have enough bandwidth for low quality video streaming the interface is still an issue.
it would be a non trivial task to packetised video into a format suitable for sending through the UART interface on a Xbee.
(it is possible but definitely not an easy project or the best use of resources.)

a far simpler solution would be to have 2 separate radio systems.
one designed for data and the other designed for video.
to minimise interference try to make sure they are both on different frequency bands. (not just different channels on the same band.)


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Offline CornelamTopic starter

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Re: XBee
« Reply #3 on: October 07, 2008, 12:49:55 PM »
My camera is sending video at 115.2 KB so  the speed is not an issue! I only wonder if i can send commands from the computer to the robot in the same time i receive JPEG compressed images from the camera. I can get about 6fps so is there anyway to send the commands to the robot and then quickly change back to emitter mode?

Offline dunk

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Re: XBee
« Reply #4 on: October 07, 2008, 02:08:06 PM »
the radio transmission speed is the least of your problems.
i strongly advise you to read the Xbee datasheet before going any further.
there is no "video in" port on the Xbee.

how are you going to convert camera data into something that can be transmitted over the Xbee's UART?

try reading up on AVRcam and CMUcam for information on one possible way to interface to a camera to a microcontroller.


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Offline CornelamTopic starter

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Re: XBee
« Reply #5 on: October 07, 2008, 02:25:44 PM »
What i have is a UART camera! It's sends data via uart  with the speed of 115.2 kbps.
I only need to know if the Xbee can transmit in the same time he receives !
Or another method to send data like wifi or another.
I really need help on this !
Thanks!

Offline dunk

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Re: XBee
« Reply #6 on: October 07, 2008, 05:40:03 PM »
Quote
What i have is a UART camera! It's sends data via uart  with the speed of 115.2 kbps.
sweet! that makes things far easier.
out of interest, which one?

the Xbee is half duplex so it can send either one direction or the other at any one time but not both together.
if i remember correctly it also has a limited TX buffer size.
because of these 2 issues you will still need to find a way to send the picture a bit at a time. break it down into pieces that fit in the Xbee's buffer, transmit then wait for data coming the other direction before sending more of the picture.

i don't know if you'll get your expected 6 frames per second or not (depends on your programming skills) but you'll definitely be able to transmit pictures this way.

you could also consider reducing the resolution of each picture. only send every other pixel, halving the image quality but also the transmit time...


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Offline CornelamTopic starter

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Re: XBee
« Reply #7 on: October 08, 2008, 03:56:24 AM »
Thank you!
I will try my best! I'm working on a robot for a international competition and it's very important for me!
But i don't know any commands to process the data from the camera via a microcontroller !
I hope if i sent the data bit by bit there won't be a problem with the speed  ???
Thanks for the help!

Offline CornelamTopic starter

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Re: XBee
« Reply #8 on: October 08, 2008, 04:33:29 AM »

Offline dunk

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Re: XBee
« Reply #9 on: October 08, 2008, 11:48:36 AM »
Quote
I hope if i sent the data bit by bit there won't be a problem with the speed 
the camera's user manual tells you how to do that bit. you can set a packet size and upload the picture bit at a time.

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Offline CornelamTopic starter

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Re: XBee
« Reply #10 on: October 08, 2008, 12:28:56 PM »
Thanks! This saved me!

Offline ArcMan

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Re: XBee
« Reply #11 on: October 08, 2008, 05:09:55 PM »
I would really like to hear about your results.  I have a couple of XBee Pro radios, but I haven't used them on a project yet.

Offline lhy_L_P

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Re: XBee
« Reply #12 on: June 12, 2010, 11:03:44 PM »
hmmm....
I also have a problem with xbee...
I'm making the detection system using loop antenna and xbee.. but I will only use one xbee as a transmitter and receiver. so the process of sending and receiving alternately. does anybody know how to use if you only use one xbee??? Help me please!!!   :'(

 


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