The project show that it is possible to build modules for remote control of long-range (a minimum of 5-8km max - global), while remaining within the amount 15PLN (electronics) and many parts are available in the home. For this purpose were used the following things:
To send DTMF commands is using MFSK modulation (called Multiple frequency-shift keying).
DTMF signal is designed to transmit as audio track - so that is ideally suited for the transmission of all audio equipment (telephones, walkie-talkies, CB radios, VoIP, etc.) In my platform I used two walkie-talkies, which practically do not lend themselves to talk (a terrible quality of the call). In this way, they got a new life, because they send a DTMF tone perfectly.
Transmitter operates as a set of two devices - shortwave and DTMF generator - phone nokia 6120. These outputs are connected to headsets (jack2.5-jack2.5 cable connected to the speaker of the Nokia and the microphone from the walkie-talkies)
Using all the audio device, among other things, we can record the robot's path for editing etc, etc.
For decoding DTMF (Nokia keyboard sound) is using MT8870 At the output of StD MT8870 high state occurs when is received and decoded the correct DTMF code, and at the terminals q1-q4 is decoded state.. Example: If you press the button on the phone - at the tip of StD at the terminals q1-q4 appears 1001 if you release the button on the phone, on StD 0 at the terminals q1-q4 appears 1001
Processing of these five zeros/ones and decoding deals ATtiny 2313 Example of program::
Motor_lp Alias Portd.2 'Okreslenie portów sterujacych silnikami przez mostek
Motor_lt Alias Portd.3
Motor_pp Alias Portd.4
Motor_pt Alias Portd.5
'Okreslenie portów wejsciowych (dekoder)
Sygnal Alias Pinb.3
A Alias Pinb.2
B Alias Pinb.1
C Alias Pinb.0
D Alias Pind.6
'Polecenia wydawane na podstawie stanów wejsciowych: Do
If Sygnal = 1 And A = 0 And B = 0 And C = 1 And D = 0 Then Gosub Prosto
Elseif Sygnal = 1 And A = 0 And B = 1 And C = 1 And D = 0 Then 'Skrec w lewo Gosub Prawo
Elseif Sygnal = 1 And A = 0 And B = 1 And C = 0 And D = 0 Then 'Skrec w lewo Gosub Lewo
Elseif Sygnal = 1 And A = 1 And B = 0 And C = 0 And D = 0 Then 'Skrec w prawo Gosub Tyl
Elseif Sygnal = 0 Then Gosub Stopp
EndIf Loop
Prosto: 'Tryby pracy silników dla poszczególnych ruchów
Motor_lt = 0
Motor_pt = 1
Motor_pp = 0
Motor_lp = 1 Return
In future there is a plans to include communications platform in the other direction, using RC5 and infrared - the platform is a guinea pig for telecommunications. Soon it will be the robot - with Sharp sensors for the front and back using RC5 and it will send information about the distance of objects from the vehicle and after a long inactivity he try to leave the maze.