RF module help

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- 8th September 2008, 02:52
greensasquatch

RF module help

I have been using the following wireless modules,

Transmitter:
http://www.e-madeinchn.com/TM1000-4.pdf
Receiver:
http://www.e-madeinchn.com/RM4SG.pdf
Encoder/Decoder:
http://www.datasheetcatalog.com/data...2/PT2262.shtml
http://www.datasheetcatalog.com/data...2/PT2272.shtml

They are 433 MHz RF transmitter / receiver pair with 4CH encoder / decoder.

So far they have worked great as I have used the receiver end connected to the PIC and the transmitting end usually hooked up to buttons. This works fine, if i press a button connected to a channel I get a steady logic level high output on the receiving end's complimentary channel.

However, now I'm trying to use them with the transmitting end hooked up to the PIC.

My first test was very simple. I have a PIC sequentially setting pins RB0 through RB3 high (exponential counting) changing once per second. I connect these pins to the 4 inputs on the transmitter, along with 100uf and 0.01uf filtering caps across the transmitters Gnd and V+. RB0 through RB3 are also connected to LEDs to show status on transmitting end.
At the receiving end I connect each pin via resistor to an indicator LED.

When I connect power one of three things happen.
- all the lights turn on at once on the receiving end although they light normally at the PIC
- all lights flicker rapidly on receiving end, normal on PIC side
- lights comes on, sometimes flickering a bit and change very slowly, not reflecting what is lit on the PIC end.

I have a feeling it has something to do with noise output from the chip even though I'm trying to filter with caps.
It seems to be quite random which of these 3 happens when I turn it on.

Anyone have any similar experiences or insight?

Image below shows setup (not all filtering caps or power connections present at this stage).
http://img247.imageshack.us/img247/3750/img5010amo0.jpg
http://img247.imageshack.us/img247/3...de031f045c.jpg
- 8th September 2008, 03:02
skimask

So, are you saying that it works fine with the encoder/decoder, but you break it if you try to connect the PIC directly to the TX module?

This subject has been gone over again and again and again here.

Do a search for RF Modules or something similar.

There has to be a hundred threads on that subject alone...at least...

Lots of good info at www.rentron.com
- 8th September 2008, 03:18
Darrel Taylor

OK, I'll take the "Dumb Test".

Is that a 6V battery?
- 8th September 2008, 03:32
mackrackit

Quote:

Originally Posted by Darrel Taylor

OK, I'll take the "Dumb Test".

Is that a 6V battery?
 

That is a link to a place if you are DUMB enough to follow through and give you email to spamers... then you are dumb!
- 8th September 2008, 05:59
Archangel

Quote:

Originally Posted by Darrel Taylor

OK, I'll take the "Dumb Test".

Is that a 6V battery?
 

I am sure it is a regulated 5 volt supply, cleverly disguised as a six volt battery . . . isn't it ?
- 8th September 2008, 06:36
greensasquatch

I've been searching the forums all day, not many people have a similar setup to mine. Those who do have not posted enough detail for me to see what I might be doing wrong. There were a few threads that had some similar problems using encoders but they were left unsolved.

I'm hoping there might be someone who is using a similar setup who can provide a link or tell me what I need to use.

I don't even need to send data here, just transmit the state of a few pins. Hints would be great too if you just don't want feel like giving away too much info.

Thanks


I am sure it is a regulated 5 volt supply, cleverly disguised as a six volt battery . . . isn't it ?

Erm, well, I was in a hurry to set it up again for a pic, that L8705 is around here somewhere....
- 8th September 2008, 07:29
Archangel

Quote:

Originally Posted by greensasquatch

I've been searching the forums all day, not many people have a similar setup to mine. Those who do have not posted enough detail for me to see what I might be doing wrong. There were a few threads that had some similar problems using encoders but they were left unsolved.

I'm hoping there might be someone who is using a similar setup who can provide a link or tell me what I need to use.

I don't even need to send data here, just transmit the state of a few pins. Hints would be great too if you just don't want feel like giving away too much info.

Thanks


I am sure it is a regulated 5 volt supply, cleverly disguised as a six volt battery . . . isn't it ?

Erm, well, I was in a hurry to set it up again for a pic, that L8705 is around here somewhere....

That's OK Justin, just a friendly poke . . . Using that as a power source, how do you get any consistancy not knowing if the voltage is over the PICs max or under the BOD min? Kinda like workin' out in the fringe, so when a problem occurs you look and ask yourself is it my code or my hardware or both? There is a trick, to making tasks easy, and it is simply, Do not make things difficult for yourself, plenty of others out there willing to do it for you.
- 8th September 2008, 11:17
mackrackit

Here is a very basic that you can build on.
Transmit snippet

Code:

TRAIN VAR BYTE TRAIN=$55 SEROUT PORTC.4,T2400,[TRAIN,TRAIN,TRAIN,TRAIN,TRAIN,9,3]

The $55 will "condition" the receiver to a mid point. Then 9 and 3 are sent.

Receive snippet

Code:

SERIN PORTC.4,T2400,[9],net

Waits for 9 and puts the next character in var net.

Get this working and then if needed add whatever encoding or chksum or bells or...

Is that coil the antenna? Looks a little long for you frequency. About 6.5 inches for 433mhz. That is wire length. not coil length. But if it works with the hardware encoder...
- 8th September 2008, 13:26
dhouston

Separate the transmitter and receiver physically by 8-10 feet.
- 8th September 2008, 15:08
bbarney

how about getting the modules out of that breadboard and at least on veraboard
- 8th September 2008, 16:32
greensasquatch

Quote:

Originally Posted by mackrackit

Here is a very basic that you can build on.
...
Is that coil the antenna? Looks a little long for you frequency. About 6.5 inches for 433mhz. That is wire length. not coil length. But if it works with the hardware encoder...

I haven't been able to get simple transmit of a high pin state working yet so i'm going to wait for serial data until that works. but thanks for the code anyway.

Yes, that is the antenna as it came prewired from the factory.

Transmitter / Receiver works fine until it's hooked up to the PIC so the antenna must be at least somewhat close. Perhaps it's a 1/2λ antenna?

Quote:

Originally Posted by dhouston

Separate the transmitter and receiver physically by 8-10 feet.

I usually work with the receiving end on the other side of the room (15 ft away).

I've been reading other threads where people are suggested to try lower clock frequency on their PIC's, buffering the outputs of the PIC and hooking up comparators. I have none of these options available and would like to know if they actually have helped before I order more parts.
- 8th September 2008, 16:51
mackrackit

Quote:

I haven't been able to get simple transmit of a high pin state working yet so i'm going to wait for serial data until that works. but thanks for the code anyway.

You might be waiting a long time.
The receiver needs "conditioned" or trained. This will basically set the internal capacitor to its mid point. The encoder/decoder chips do this. So if you just send a HIGH, the receiver may already be HIGH and does nothing. The receiver is always receiving something from somewhere, it needs a starting point. dhouston can explain this better or correct me.
- 8th September 2008, 18:50
dhouston
Read this...
- http://davehouston.org/RFTipsTricks.htm
Using the encoder/decoder chips complicate things. Bruce Reynolds posted some code here a few months back showing techniques for working with standalone encoder/decoder chips. The principles will be the same. You'll need to look for the silence that occurs between codes and then listen for the start of the following code.