433mhz rx tx module problem with MCU 89C2051

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ronydc

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dear friends,,

A SERIOUS PROBLEM I AM BEEN FACING..

I brifely describe my arrangement as under.

AIM: TO SEND A serial DATASTRING FROM PC AND RECEIVE IT on the LCD screen. ( 16x2) WIRELESSLY.. USING 433 MHZ TX RX MODULES.

PROBLEM: I M RECIVING ONLY GARBAGE SOME TIME ON LCD SCREEN OR MOST OFF THE TIME -- just nothing.. on lcd.

I brifely describe my arrangement as under.

Tx side --> the pc serial port goes to MAX232 IC and the out of the max232 is given to the st433 TX module.

RX SIDE --> ST433 Reveiver module and the out of the module is given to the . MCU 89C2051. the program inside the mcu shows the DATA typed on the keyboard of the pc to the 16x2 LCD.

PLEASE some one.. tel me.. where i m wrong.

( tested my program inside the mcu and its perfact -- it works well when connected directly to lcd-- but not wirelessly)

note: tried with reduced baud rates up to 300.

If some one suggests USING HT12E.. THEN PLEASE SHOE ME THE METHOD GIVING MY INPUT TO THE ENCODER IC FORM PC SERIAL PORT.( OFCOURSE AFTER max232)

-- Rony
 

first of all, why do you have both a rs232 transciver and this st433 TX module on to your MCU ??

secondly, why why are you using 433Mhz modules ??
 
Try to perform the following test:

Take another MAX232 and connect it to the 433-RX module, then feed the output from MAX232 (RS-232 level) back to the PC’s serial port (rx-pin) ..
Now when you open Hyperterminal, type something – you should see on the PC’s screen ECHO from whatever you just typed ..
This will ensure that your wireless channel is working ..

Can you do it, please ..

Rgds,
IanP


PC(TX) => MAX232 => 433TX - - - - - 433RX => MAX232 => PC(RX)
 

Hi ronydc,

I think you must consider what happens to the serial data when passed through MAX232. It gets inverted and so a high is represented by a negative voltage (-12V) and a low by positive voltage(12V). So when you receive this at the receiver module what you get is the inverted data. The RS-232 protocol requires that the TX line, which is connected to the RX line of MCU, is high in idle state. But in your case it is idle low since it is inverted. So try inverting the receiver module output before giving to MCU.

Also I have heard that the input of an RF TX module is AC coupled. So if your data consists of long zeros(because after passing through MAX232 it becomes ones) they may not be transmiteed successfully since DC is blocked unless you are using a high baud rate.

Please correct me if anyone feels I went wrong somewhere.
 

IANP HAS SHOWN GOOD WAY FOR THE CHECK.
i will do it and post the results.

but first of all i feel.. DOES some one surely knows that, we can use the modules directly to the mcu or not.
because if we cant use the tx-rx modules directly with the MCU ( WITHOUT HT12 ICS) then there is no question of getting the data anywhere out as the result ( at RX )
IANP whats your comments. please.
 

I can’t see any reason why these 433-modules shouldn’t be directly connected to MCUs ..
There are plenty of working system everywhere and they don’t have problems – except maybe for some interferences from another 433MHz system working somewhere nearby (eg. roller-door controllers) ..

Rgds,
IanP
 

As a problem of crosspost threads like this, it stays unrelated to the points, that of been already mentioned in the same regard.

DOES some one surely knows that, we can use the modules directly to the mcu or not.
Click to expand...
I surely know, how reliable radio data links are operating, see your previous thread.

Unfortunately, the exact RF module type and supplier hasn't been mentioned ("ST-433" isn't unique), but similar ASK modules specify, that the signal duty cycle should be between 33 and 66%, which clearly doesn't work with UART data. I also noticed, that edaboard users reported in one of the various previous "RF module" threads, that they managed to operate a link with special tricks, e.g. encoding one data byte to two "DC balanced" UART characters where each original bit is followed by an inverted bit. You can understand this method as a kind of "software manchester encoding". It solves the problem of generating a DC balanced data stream, but doesn't provide a reliable synchronization, which has to be done on a bit level.

As an additional remark, do you actually know, what's the idle state of your RF modules? Some modules have a low idle state, they would be permanently transmitting when connected to a TTL UART level.
 

I think problem is with the modules..

I am familiar with 433mhz and 315mhz modules. The quality of module is an important factor. My modules cost me about Rs:350 (Indian rupees) it works fine with HT12D an HT12E but not with MCU. Recently I bought a new standard module from Delhi it works fine with MCU. That is why i am strongly recommend you to buy standard modules instead of low cost.


to use these modules with MCU is.
Reduce baud rate to below 70
Use invert mode UART
Transmitt 0x55 or 0xAA first before transmitting the actual data



You can also try zigbee/bluetooh module.

Wish you good luck..
 

anandpv2009 .. please share the address of the place or web address of the place you got the module that worked well with MCU.
I RESIDE IN GUJARAT.

- Rony
 

I don't know the actual shop name because I bought the module through my friend..

But still you r lucky


Sunrom Technologies
33, 1st Floor, Yash Niketan Complex
Opp. Khokhra Police Station
Khokhra Circle, Maninagar(East)
Ahmedabad - 380026, Gujarat, India

Their site addr.: https://www.sunrom.com/

See the 'RF & Wireless' section
Click to expand...

Actually I am frm south india(Kerala). It is very difficult to get RF modules / components in my district.


Good Luck..
 

dear anandpv2009 . when i inquired at sunrom i got the following reply.

-->it will only work with encoder/decoder like ST12, ST14, HT12E/HT12D,
Check this chips datasheet for further details.
Regards,
Viral.

the above reply makes it all clear.

but, but but,, i have got conform information form a very senior person. that there are RF TX-RX MODULES those can work. directly with MCU. ( CONFORM NEWS)
They have high quality and direct drive capacity.
we just have to find out where those are avilable.

--CAN SOME ONE DO IT CONFORMLY..? IT WILL BE VERY HELPFUL TO THE "MANKIND".

THANKS,
---Rony.
 

RF modules, that contain an own µC to encode/decode the data can surely work with an UART interface. Furthermore, any module can work with a MCU, if the processor encodes the data stream according to the module's requirements.

At sunrom, modules that can directly work with UART interfaces are designated "RF modems" in contrast to "RF remote control" modules, that require Holtek encoders or a special preprocessing by a MCU.

Another example of UART capable RF modules are the EasyRadio products from LPRS https://www.lprs.co.uk/
 

Hey look at the RF modem section....
I don't have any previous experience with the above company but my friends.

From their site:


I know the above Modem is also a type of module which using chip/s for proper reception/transmission.

Ok RONY I will try to find a solution for your problem....
I will post it as soon as possible...


See my project.. In this project two RF modules are used for full duplex communication.
 

ANAND
FOR THE NAME OF THE PROJECT YOU JUST SHOW US THE PICTURE .?
THANKS ANY WAY.
MOD: Do not use "Caps" Unless mandatory. You'll be warned next time.
 

I am just show the picture to prove my RF modules works fine...

I am willing to give you program or circuit diagram(for pic MC) which works fine with my Modules..

See the link below..
 

Dear Friends

the main problem that you will face when you are using those modules will be that most of the module's output cannot directly drive the pin of the MCU. so you need to place any 74xx ics between the module and the controller. try sending the same data many times so that the receiver will surely receives the sending data an write program in the receiver MCU to take care of this

thanking you


Ml
 



I think 'microlab' suggestion is to use a not gate (7404). I tried it without not gate by using the invert command in the software uart init with my previous modules. But it works only with low baud....


Ok rony my final answer is, use a RF modem which is available frm sunrom electronics.....
 

Not sure how you sent the data string. I mean when you want to send, says two bytes, then you send two bytes without changing anything. If so, your problem should be there. Wireless communication is different from wired comm because of noise. Normally, you can not treat the data in wireless comm in the same way as you do in wired comm. You need to encode the data before sending and decode it after receiving to get the original data. I used Manchester encoding when using wireless modules to send and receive data. The baud rate I could archive was up to 1200 bps if i remember correctly. Hope above information is useful for you
 

Can you Please send me the Manchester encoding code for the 8051 mcu please .?

that will be the great help.

-- Rony.
 

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