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RF600T circuits

:: EPE Chat Zone ≠:: ≠Radio Bygones Message Board :: » EPE Forum Archives 2005-2006 » Archive through 08 October, 2005 » RF600T circuits « Previous Next »

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Amr_bekhit
Frequent Contributor
Username: Amr_bekhit

Post Number: 69
Registered: 06-2005

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Posted on Wednesday, 05 October, 2005 - 04:17 pm:   Edit Post Delete Post Print Post

(This post is in reply to an email by Chuckiboy asking about the RF600T)

To start off, I was given a remote control airship by my physics teacher because he had lost the remote control for it. I had seen radio modules in Farnell and thought them to be an easy way to send and receive data via radio. However, after several simple tests where I tried to send a byte of serial of data from one end to another, I deduced I couldnít just use the radio modules by themselves and I needed some sort of support chip. This is why I bought the RF600T.

The circuit diagram below shows my transmitter circuit. Basically, I programmed a PIC to send a single character as a constant stream to the RF600T and the RF600T is connected to my transmitter module.

RFTX

On the receiver side, I have a receiver radio module hooked up to an RF600T, which then outputs directly to a PIC or a PC serial port. For my first tests, I connected it to the serial port of the PC.

RFRX

Now, both RF600Tís are configured to operate at a 9600 baud rate. This is done by connecting pin 9 of the chip to 5V via a 100k resistor.

Just a brief note on building the circuit on breadboard: everywhere that Iíve looked where people ask if itís ok to build radio circuits on breadboard, others have recommended against doing so as the capacitance of the tracks can filter out the high frequencies present in radio circuits. I set up these 2 circuits on breadboard and providing you DONíT plug the antenna pin of the radio modules in the breadboard , you should be ok.

Anyway, so I set up the two circuits and programmed a PIC to send a character to the transmitter in a constant stream. The code for the PIC in PICBASIC (oh, how I love it!) is shown below:

Device = 16F628A
XTAL = 4

ALL_DIGITAL=true

While 1=1
SerOut PORTA.1, 84,["A"]
Wend

End


As for the receiver, I connected the serial output from the RF600T to the PC serial port and booted up HyperTerminal. After I switched on the two circuits, I found HyperTerminal doing the following: it outputs a long stream of rubbish, pauses for a second, then outputs some more rubbish and pauses and so on. I thought that perhaps the fact that I was streaming the data meant that the serial clocks might be going out of sync. I tried adding a small delay in between sending one character and another:

Device = 16F628A
XTAL = 4

ALL_DIGITAL=true

While 1=1
SerOut PORTA.1, 84,["A"]
DelayMS 100
Wend

End


This worked fine and I got the characters I wanted on the screen. Unfortunately, when I tried decreasing the time delay between characters to enable me to send a bit faster, I started getting errors in the data received. 100ms seemed to be the optimum. I donít know why this is, but Iím guessing it may be the serial clocks going out of sync. I also reckon that the RF600Tís operate at their best when they are used in conjunction with transceivers and not just a transmitter on one side and just a receiver on the other. I think that the chips do rely on being able to handshake between each other in order to operate properly. Because of this, I bought some EASYRadio modules and started using them. However, I found that these too, refuse to stream data accurately and I have to send the characters one at a time with a small delay in between and do not handshake at all between themselves.

Anyways, thatís my work with the RF600Tís.

--Amr
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Chuckieboy
Regular Contributor
Username: Chuckieboy

Post Number: 21
Registered: 05-2005


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Posted on Wednesday, 05 October, 2005 - 09:24 pm:   Edit Post Delete Post Print Post

Amr
I shall look forward to palying with these little chappies. But before I do a shall finish off my PCB'S which will be the test bed for them becasue if you build them up on breadboard The long tracks inside these types of prototyping board introduce large capacitances /inductances to the circuit which can badly distort / detune rf signals. I shall include a serail port and input's t controll send data via another PIC chip. Once done i shall upload here for anybody esle who want to start playing around.
Thanks to Amr who gave me the incentive to carry on where i left it. Well it was all in the pipeline but never got round to do anything with it

cheers
chuckieboy

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