« previous topic   next topic »
Pages: [1]   Go Down
Author Topic: XBee RSSI Signal  (Read 1453 times)
0 Members and 1 Guest are viewing this topic.
UNTEngineer
Texas, USA
Offline Offline
Jr. Member
**
Karma: 0
Posts: 53
Arduino rocks!!
View Profile
« on: November 15, 2012, 09:35:35 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Could I use the RSSI signal to determine signal strength? Can someone suggest a simple circuit that I can visually display the signal using a LED bar graph.
Logged
Working on a Smart Home Management System. Visit my blog: http://tae09.blogspot.com/ to find out more, and to keep track with the project.

oric_dan
the land of sun+snow
Offline Offline
Faraday Member
**
Karma: 149
Posts: 2790
View Profile
WWW
« Reply #1 on: November 15, 2012, 09:50:09 pm »
 Bigger Bigger Smaller Smaller Reset Reset
According to my d/s, RSSI is a PWM output. You can filter this using a simple RC low-pass filter, and feed
to an LM394 or LM3915. They apparently still make these things.

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_24230_-1
http://www.jameco.com/1/1/2533-lm3915n-1-lm3915-dot-bar-display-driver.html

For ckts, do a google image search on LM3914 or LM3915,

http://www.google.com/imghp
Logged

UNTEngineer
Texas, USA
Offline Offline
Jr. Member
**
Karma: 0
Posts: 53
Arduino rocks!!
View Profile
« Reply #2 on: November 15, 2012, 10:41:35 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Well I have a PCF8574N. Will that work?
Logged
Working on a Smart Home Management System. Visit my blog: http://tae09.blogspot.com/ to find out more, and to keep track with the project.

oric_dan
the land of sun+snow
Offline Offline
Faraday Member
**
Karma: 149
Posts: 2790
View Profile
WWW
« Reply #3 on: November 16, 2012, 01:03:12 am »
 Bigger Bigger Smaller Smaller Reset Reset
Ok, take at look at the chips I mentioned and see how they compare to your [what I presume is an]
I2C expander. You want a display, no?
Logged

UNTEngineer
Texas, USA
Offline Offline
Jr. Member
**
Karma: 0
Posts: 53
Arduino rocks!!
View Profile
« Reply #4 on: November 16, 2012, 01:42:04 am »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: oric_dan(333) on November 16, 2012, 01:03:12 am
Ok, take at look at the chips I mentioned and see how they compare to your [what I presume is an]
I2C expander. You want a display, no?

I looked at the LM3916, and I realized the difference after I posted that. One is a multiple LED/LCD driver and the other is an I2C expander for an LCD.

What values would you suggest for the Low Pass Filter?
Logged
Working on a Smart Home Management System. Visit my blog: http://tae09.blogspot.com/ to find out more, and to keep track with the project.

UNTEngineer
Texas, USA
Offline Offline
Jr. Member
**
Karma: 0
Posts: 53
Arduino rocks!!
View Profile
« Reply #5 on: November 17, 2012, 08:51:03 pm »
 Bigger Bigger Smaller Smaller Reset Reset
bump!
Logged
Working on a Smart Home Management System. Visit my blog: http://tae09.blogspot.com/ to find out more, and to keep track with the project.

oric_dan
the land of sun+snow
Offline Offline
Faraday Member
**
Karma: 149
Posts: 2790
View Profile
WWW
« Reply #6 on: November 17, 2012, 09:12:35 pm »
 Bigger Bigger Smaller Smaller Reset Reset
You need to know the PWM frequency out of the RSSI pin, and then select a cutoff frequency
roughly 10X lower, according to

F3db = 1/(2*pi*R*C)

Use R=4.7K or 10K as a starting point and calculate C accordingly. That's where I'd start.
Logged

betomax
0
Offline Offline
Newbie
*
Karma: 0
Posts: 7
Arduino rocks
View Profile
« Reply #7 on: November 17, 2012, 10:19:52 pm »
 Bigger Bigger Smaller Smaller Reset Reset
take a look to dev interface schematic, were a lm339 is used to drive 3 leds (basic comparator) feed with rssi output through RC filter


http://ftp1.digi.com/support/images/XBIB-R-dev%20schematic.pdf
Logged

Jack Christensen
Grand Blanc, MI, USA
Offline Offline
Faraday Member
**
Karma: 71
Posts: 3510
CODE is a mass noun and should not be used in the plural or with an indefinite article.
View Profile
WWW
« Reply #8 on: November 17, 2012, 11:16:32 pm »
 Bigger Bigger Smaller Smaller Reset Reset
I'm working on a project right now that does this. Connect the XBee RSSI pin to a digital input pin and use pulseIn() to read the PWM pulse width.

S1 or S2 XBees?
Logged
MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

Pages: [1]   Go Up
« previous topic   next topic »
Jump to: