RF Transmitter/Reciver

**Fredrick** · - 11th February 2008, 19:04

Yes i have lookt at Rentron but 2 transmitter and 2 recivers + 2 anntena coast $111 and at parallax $109,95 with antenna.

**mackrackit** · - 11th February 2008, 19:43

Originally Posted by Fredrick

Yes i have lookt at Rentron but 2 transmitter and 2 recivers + 2 anntena coast $111 and at parallax $109,95 with antenna.

OK, but the antennas from parallax do not look very good (very short ), the ones from rentron are 1/4 wave.

As I said before, the antenna will make all the difference for long range.

Let us know how it goes.

**Fredrick** · - 11th February 2008, 19:54

Yes i will inform how it goes, and maybe i will come with some questions on the PBP program for the recivers and transmitter.

**Fredrick** · - 14th February 2008, 08:10

Are the Linx RF modules FM och AM?
Can´t find anything in the datasheet?

**mackrackit** · - 14th February 2008, 08:54

Neither, More like CM.
From the data sheet

When a logic ‘1’ is present on the DATA line and the PDN line is high, then the
Power Amplifier (PA) will be activated and the carrier frequency will be sent to
the antenna port. When a logic ‘0’ is present on the DATA line or the PDN line is
low, the PA is deactivated and the carrier is fully suppressed.

So, the only thing they can transmit is bits, think of Morse Code. ON OFF
That is why they work so well for serial communications.
Also, that is the reason for sending a "train" signal (010101010101) allows the receiver to balance the internal capacitor before receiving the real data.

I think the correct way of saying it is Carrier Present - Carrier Absent

**dhouston** · - 14th February 2008, 12:26

Originally Posted by mackrackit

I think the correct way of saying it is Carrier Present - Carrier Absent

Or OOK (On-Off Keying), ASK (Amplitude Shift Keying) or AM (Amplitude Modulation). And FSK (Frequency Shift Keying) works much better but costs much more.

**Fredrick** · - 14th February 2008, 20:45

Thank you.

Now i have recived the Parallax RF modules and write this test programs

Transmitter PIC16F628A whit Internal RC OSC at 4 MHz

Code:

<html>
<head></head>
<body><!--StartFragment--><pre><code><font color="#008000"><i>
</i></font>CMCON = <font color="#808080">7 </font><font color="#008000"><i>'Alla I/O Digitala
</i></font>LEDPin <font color="#000080">VAR </font>PORTB.<font color="#808080">0
</font>TransmitterPIN <font color="#000080">VAR </font>PORTB.<font color="#808080">4
</font><font color="#000080">INCLUDE </font><font color="#FF0000">&quot;modedefs.bas&quot;
</font>Counter <font color="#000080">VAR BYTE
</font>Synk <font color="#000080">VAR BYTE
</font>Synk = <font color="#808080">$55
</font><font color="#000080">DEFINE </font>CHAR_PACING <font color="#808080">1000
</font>Counter = <font color="#808080">0

</font>Main:
    <font color="#000080">HIGH </font>LEDPin
    <font color="#000080">PAUSE </font><font color="#808080">100
    </font><font color="#000080">LOW </font>LEDPin
    <font color="#000080">PAUSE </font><font color="#808080">100
    
    </font><font color="#000080">SEROUT </font>TransmitterPIN,T1200,[Synk,Synk,Synk,Synk,Synk,Synk,<font color="#808080">9</font>,Counter]

    <font color="#000080">HIGH </font>LEDPin
    <font color="#000080">PAUSE </font><font color="#808080">100
    </font><font color="#000080">LOW </font>LEDPin
    <font color="#000080">PAUSE </font><font color="#808080">100
    
    </font>Counter = Counter + <font color="#808080">1
    </font><font color="#000080">PAUSE </font><font color="#808080">600
</font><font color="#000080">GOTO </font>Main
<font color="#000080">END 


</font></code></pre><!--EndFragment--></body>
</html>

Reciver PIC16F872 with 20 MHz OSC

Code:

<html>
<head></head>
<body><!--StartFragment--><pre><code><font color="#008000"><i>
</i></font><font color="#000080">DEFINE </font>OSC <font color="#808080">20
</font><font color="#000080">DEFINE </font>LCD_COMMANDUS <font color="#808080">3000   </font><font color="#008000"><i>'Set command delay time in us
</i></font><font color="#000080">DEFINE </font>LCD_DATAUS <font color="#808080">200       </font><font color="#008000"><i>'Set data delay time in us

</i></font><font color="#000080">INCLUDE </font><font color="#FF0000">&quot;modedefs.bas&quot;
</font>Counter <font color="#000080">VAR WORD
</font>ReciverPIN <font color="#000080">VAR </font>PORTC.<font color="#808080">0
</font>ADCON1 = <font color="#808080">7 </font><font color="#008000"><i>' Alla digitala
</i></font><font color="#000080">PAUSE </font><font color="#808080">500

</font>Main:
    <font color="#000080">SERIN </font>ReciverPIN,T1200,[<font color="#808080">9</font>],Counter
    <font color="#000080">GOSUB </font>LCD
<font color="#000080">GOTO </font>Main

LCD:
    <font color="#000080">LCDOUT </font><font color="#808080">$FE</font>,<font color="#808080">1  
    </font><font color="#000080">LCDOUT </font><font color="#808080">$FE</font>,<font color="#808080">$80</font>,#Counter
    <font color="#000080">PAUSE </font><font color="#808080">500        
</font><font color="#000080">RETURN

END 
</font></code></pre><!--EndFragment--></body>
</html>

It´s working very well whit in the rance of 50 - 60 meters whit the transmitter indoors and the reciver outdoors, but when i take the reciver also indoors in a house 50 - 60 meters away from the transmitter the counter on the reciver display starts to show wrong numbers sometimes but it´s still counting... but whit the reciver outdoors it does not miss a single number whit in 50 - 60 meters.

Any idé how i can to improve my code?

I´going to do some more tests to tomorrow, it´s soon time to sleep here in sweden...

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