problems with RF 434Mhz and 315Mhz modules

Hello Experts

I am writing this post because a couple of weeks ago, I bought the modules 434 transmitter and receiver from sparkfun page, and I read the manuals posted in the page of this devices but nothing I tried until now, let me receive data from transmmitter to receiver.

I don’t know why is this because the manual says it is easy to use, I have connected the TX to the transmmitter and the RX to the receiver but nothing happen, can anyone help me with any idea? or advise? (also the modules 315 are not working, either)

graphic:

picTX---->transmitter ~~~~~ receiver---->pic RX

thank you

Hi rald,

At what baud rate you are testing the wireless modules?

Because this modules works upto 4k baud rate.

if you have oscilloscope then check with RX module connected to scope input, Connect 5v to TX data pin, you should get logic high on to oscilloscope, if this happens then your module are working fine.

Google and search this forum about OOK modulation. This RF modules usually don’t work on just straight serial data. A preamble and bit encoding is required.

For a quick test send a continuous stream of altering bits (ASCII ‘U’ works).

Hello guys

thank you very much for yours answers.

abitkin: I am using the rate at 4800bauds but is not working, the program that I am using is very simple, I send the number 1 in ASCII and the receiver if get this number have to turn a led on, and retransmit to a serial port using the TX port, this TX is conected to my laptop and I see the received character on my computer, but nothing is happing, I don’t know what should be happing…

waltr: yes, I read about this coder and decoder but I am not able to use other IC because the price and the space in for my project, this project is my finish degree project and have to be install into a very small space, but if you explain to me how this litter divices work probably I can try to imitate their behavor using a PICs, I tried to find information about those IC but, until now, this information it has been unuseful.

I am against time, I tried with filters, more power (9 volts) and sent independent bits.

please any help is well appreciated.

thank you

Have you tried sending ‘U’ continuously, as was suggested?

hi leon_heller

no, I have not tried to send “u”, but I used the “1”, is there any difference between this characters?..

and also, my program is sending the number “1” every 500ms it is a bucle. Do you have any idea? let know it and I will try.

thank you

rald:
hi leon_heller

no, I have not tried to send “u”, but I used the “1”, is there any difference between this characters?.. and also, my program is sending the number “1” every 500ms it is a bucle. Do you have any idea? let know it and I will try.

thank you

First read the 2 posts re: the AGC timing of these type of modules here …

viewtopic.php?f=13&t=30114

Then what I would try is reducing the time between bytes sent from 500 msec to perhaps 20-40 msec.

What do you have for test equipment ? Is there anyway you can monitor the output of the Rx line into your PIC to see if there’s any activity there ? Anyway to verify your “Tx PIC” is actually sending the expected bitstream ? Can you directly connect the “Tx PIC” output pin so the bitstream is sent directly to the “Rx PIC” input pin to verify all the coding works as expected ?

Sending a ‘1’ won’t work. You need an NRZ signal, such as alternating 1s and 0s, which you get by sending ‘U’ continuously for test purposes.

leon_heller:
Sending a ‘1’ won’t work. You need an NRZ signal, such as alternating 1s and 0s, which you get by sending ‘U’ continuously for test purposes.

I agree sending a ‘U’ would be better but an ASCII 1 is a 31h or 00110001b which should still work. A ‘3’ would be better than a ‘1’ and a ‘U’ better still. (@ the OP : note it’s a capital U)

Has anyone tried connecting the RF output directly to the RF input for one of these pairs ? I have no idea of what the max RF input allowed is on one of these ? I believe the output could be in the range of +10 dBm. I wonder if the OP could have damaged the receiver when he did this ?

the problem with ascii is that there is no embedded clock to recover, so a byte with a lot of sequential 0’s or 1’s can get smeared into junk. NRZ/manchester has a transition for every bit so you know it’s just 1 bit, not a cluster. I didn’t see what the sending bps was or if the OP has an o’scope. Without an O’scope, it’s like poking around in a dark cave with a sharp stick to find out what’s growling. If you look at the msg’s I posted previously on these tx-rx data links you can see that the agc needs to be “trained” to your signal level. A single byte transmission is impossible. Try dropping your transmission rate down to 1200, 600 and 300 bps so your receiver’s pulse edges are clear; (at 4800 you have a trapezoid pulse out of the rx ) Try sending a dozen capital U’s and see it anything is decoded by your receiving pic.

Hello everyone

I tried send the letter “U” using 1200 bauds, 600 bauds but the interference is higher, so I tried to understand how works the HT12E and what I understood was that this device send the data to 38kHz, that is faster that speed supported by the module (4800) so, what I am thinking to do is send “1” repeatedly as this HT12E does and attach my data into other byte, but I really think that use the RS232 protocol is not appropiate to work with this modules. Said this, what do you think about start a new protocol developed me to be used with this modules? it is a crasy idea?

regards

google “atmel manchester basics” and download the document “doc9164.pdf” for the clearest description on writing a manchester coder and decoder in an language on any uController you like.

I have these modules. Ive found sending one character over and over again does not work as a test. Try ‘ABC’ over and over. It is easy to debug if you have somthing constantly transmitting, and another microcontroller giving a real-time output of what it recieves… e.g. Serial monitor if you are using an Arduino.

Hello N314

I decided to stop losing time and I bought IC HT12e and d, I am waiting to get it to start testing the system and I hope this will fix the problem… I think that the problem is an interference frequency, but the problem is that if I used any bauds I am still receiving interference, no matter if I used a filter I can watch a lot of interference…