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Zigbee/Xbee Signal Strength Measurement (RSSI)

P: 2
Hey guys, I was kind of hoping that someone could help me out with a project I am working on for school...

We are desigining a robot that someone will approach, and the robot will ask the user if they would like to go to room A, B, or C. (keep in mind all the rooms are in a striagh hallway with no turns).

We have decided to put Xbee modules at each room and an additional xbee module on the robot. In front of each room, we would like to take a signal strength reading from all 3 stationary xbee modules and kind of "tringulate" the robot's location this way (in front of each room, the RSSI of each xbee modules theoretically should be noticably different).

I understand that the pin 6 of the xbee module is the RSSI pin, but i need to know how to set the xbee module mounted on the robot to communicate with the 3 stationary modules and take readings from stationary module. It probably has to do with setting the robot's module to broadcast mode.

Also i have read that i may need to use a PWM filter, but am not sure since I want to receive the signal strength at the sender, not the receiver.

Any help would be greath, thanks!
Nov 16 '08 #1
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16 Replies


RedSon
Expert 5K+
P: 5,000
Sorry... we get Zigbee and Xbee questions from time to time, but we have no experts on this forum with enough knowledge to be helpful...

Google is your friend.
Nov 17 '08 #2

P: 2
Alright, thanks anyways!
Nov 17 '08 #3

Plater
Expert 5K+
P: 7,872
If you use maxstream's XBEE_API to communicate, every communicated message will contain the RSSI value in one of the bytes in the frame.
The RSSI is not a "strength" measurement so much as it is a measurement of interference. i.e. The smaller the number the better...
Nov 18 '08 #4

markmcgookin
Expert 100+
P: 648
If you use maxstream's XBEE_API to communicate, every communicated message will contain the RSSI value in one of the bytes in the frame.
The RSSI is not a "strength" measurement so much as it is a measurement of interference. i.e. The smaller the number the better...
Someone tie plater's showlaces together ... we can trap him here and he can answer all the xigbee questions
Nov 19 '08 #5

Plater
Expert 5K+
P: 7,872
If you do a search on "xbee" in this forum, you will see i pretty much DO answer all the xbee questions (my experiance is only with the xbee, not with other zigbee protocol implementations)
Nov 19 '08 #6

P: 3
@Plater
hi plater
i'm new here,my project is to send the RSSI value to the base station to localize and track the xbee tag ,i have 4 xbee reader(fixed points),now i'm tring to communicat at first between the tag and one reader ,the problem that i could not read the messag receive in api mode to find the bit 7 rssi.
now my idea is to put the xbee tag in api mode but receive the message from xbee reader with transparent mode(api=0),is this way is right i mean can i communicat between xbee - api=1 and other api=0?????????
Feb 24 '09 #7

Plater
Expert 5K+
P: 7,872
If all you are doing is trying to find the RSSI of surrounding devices then I recomend using the AT ND command. Check it out in the manual, it just scans for nearby XBees giving serialnumber, rssi, etc for each device it finds.
Feb 24 '09 #8

P: 3
@Plater
thanks plater for feedbak,but may be ATND indicates the RSSI of the last hop only.i read many times the packet receive with api is better to read the rssi but i could not communicat between 2 xbees with api.
Feb 24 '09 #9

Plater
Expert 5K+
P: 7,872
ATND does a scan against ALL XBee devices it can find. The RSSI provided is the measurement between the XBee that issued the command and the the XBEE it found (Note: It can find and return multiple XBees/RSSIs with a single call)

If you want to read the RSSI from an API packet, you have to get the remote XBEE to send a message back.
Feb 24 '09 #10

P: 3
@Plater
thanks plater again for feedback,that is i meant in my first letter to you,to use the api mode my idea is to send message from remot xbee( which present xbee reader as i told you befor) in transparent mode api=0,and the xbee tag receive this message in api=1(as a packet)to find the accuracy rssi
is this idea right???
Feb 24 '09 #11

Plater
Expert 5K+
P: 7,872
I am not sure you can do that, as the XBee's internals handle the packet formationing.
Feb 25 '09 #12

P: 12
@dove
.[/quote]

hi plater ,ATND have not contain the RSSI in xbee seres 2,pliz clarify what do u ment do u main(youto get the remote XBEE to send a message back)???
Feb 25 '09 #13

Plater
Expert 5K+
P: 7,872
Ahh, there's the key phrase everyone was leaving out.
You are using the series2 modules, which use the Zigbee mesh.

You're on your own with those, as I haven't used them.
Their manual is found here though: http://ftp1.digi.com/support/documen...90000976_B.pdf
Feb 25 '09 #14

RedSon
Expert 5K+
P: 5,000
We love Plater!
Feb 25 '09 #15

P: 12
@Plater
dear,
i'm trying to sendATND from one xbee through ATMEL89c052 to another xbee,
the second just retriev the first line(MY),it should retriv 10 lines,by the way ,sending +++ is success with retriv ok.do you have any idea
Jun 20 '09 #16

Plater
Expert 5K+
P: 7,872
Unless there is something new in the series2 for sending AT commands to a remote modem, the AT commands generally only apply to the local modem
Jun 22 '09 #17

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