Radio frequency beacons for the blind.

Crystalionx

I am trying to develop an RF beacon for blind people at the school where I am studying electronics technology.· My idea was to identify certain points with morse code signals - and then transmit the signals from one BS2 (transmitter) to another (receiver) utilizing the RF digital components.· For this purpose, I first adapted the basic Parallax alarm signal code to produce the dit-dat 'A' morse code letter, as can be seen below.· I had the belief that this program could be represented as a string and transmitted by means of the SEROUT Command.· If this is indeed possible, how can the morse code signal and the SEROUT command be combined.· If this is not possible, is there any way to send a morse code signal by means of ASCII or other data transmission?· I did not notice a morse code program in the control and command projects book, but I never got that to operate - though I might go back to it if there are no other suggestions.· Anyway, as Dave from Parallax has suggested, I am open to all possibilities should anyone of the forum wish to comment.· Thanks.

By the way, I am the same guy who had the problem with getting the sonar ranger to beep at specific distances - I appreciate your help in that regard and that component will, hopefully, be part of the RF beacon system.




' What's a Microcontroller - ActionTones.bs2
' Demonstrate how different combinations of pause, duration, and frequency
' can be used to make sound effects.
'{$STAMP BS2}
'{$PBASIC 2.5}
DO
·
duration VAR Word
frequency VAR Word
DEBUG "Alarm...", CR
PAUSE· 500
FREQOUT 9, 250, 1500
PAUSE 500
FREQOUT 9, 750, 1500
·
LOOP
·
' SEROUT.BS1
' This program transmits the string "ABCD" followed by a number and a
' carriage-return at 1200 baud, inverted, N81 format.
·
·
·
SYMBOL· SOut··········· = 1
SYMBOL· Baud··········· = N1200
·
SYMBOL· value·········· = W1
·
·
Setup:
· value = 1
·
Main:
· SEROUT SOut, Baud, ("ABCD", r )
· value = value + 1
· PAUSE 250
· GOTO Main
· END
=
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Chris Savage

Hello,

·· You can send Morse Code tones via serial/RF, per se.· What you can do is send the values, and have the receiving end decode and play the Morse Code tones.· Interestingly, you said you'd be using a BS2, but you have a BS1 code sample·pasted which will not work on the BS2.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Tech Support
csavage@parallax.com

Crystalionx

Chris - when you say 'send the values' do you mean high/low signals with pauses to indicate morse code signals?· Or are you referring to the morse code subroutine described in the comm projects book?· By the way, the BS1 code was just in the serout program demo.· Also, can the speak jet chip be utilized with the RF Digital System to transmit the voice messages from one BS2 to another BS2?

PJAllen

· I suggest using a BS-2 approach and have the "beacon STAMPs" sending their own unique DTMFs·( DTMFOUT ) and likewise your "receiver STAMP" listening for DTMFs, when it "hears" a DTMF it would react based upon that.·
· You could couple the·"beacon STAMPs"·into "wireless microphone"-type FM-transmitters and use a standard FM-radio coupled to a DTMF tone-decoder circuit and that to the "receiver STAMP".
· Similarly, and perhaps somewhat easier, you could forego DTMFs and use FREQOUT, too, but you'll still require a tone-decoder with your "receiver STAMP."· Simple 567-type tone decoders are more available.

· The trick would be to keep the transmitters far enough apart so that there wouldn't be significant interference (receiving two tones at once.)· If this is a proof-of-concept assignment, then being in different rooms at ends of a hallway will likely be sufficient.

· Here's a· link to a LM567 datasheet --
http://www.jameco.com/wcsstore/Jameco/Products/ProdDS/24395.pdf

· Edit/Addendum --
I did some looking around for you and bgmicro.com, an excellent·hobbyist-oriented supplier, sells the "8870" DTMF Decoder for $4.00.· Go to http://www.bgmicro.com·and then type·8870 in the search box.·
They have the datasheet in the Documents tab, or you can go there from here:
http://www.bgmicro.com/pdf/ics8870.pdf


Post Edited (PJ Allen) : 11/24/2005 3:54:12 PM GMT