Do we need Manchester coding while 433 module data transmission in UART

[demetal]

Hi,


I would like to know whether is there an alternative method where we dont need to use Manchester coding for uart transmission of Data from a keypad in PIC by using RF 433 Module.....

 

[wp100]

Hi,

If you have used the 433 modules you soon realise that there are lots of other signal being received other than your own, so you must send an identifier your receiver can recognise.

The Manchester code worked ok when I tried it, so why reinvent the wheel ?

 

[betwixt]

It's because Manchester encoding has a transition from 0 to 1 and also from 1 to 0 in every bit so the number of ones and zeroes is always equal.
In a radio transmission system the receiver has to be able to differentiate between 1 and 0 and this is unreliable or even impossible if it can't either find the mid frequency between them (FM) or extract a clock point (AM). For example, imagine an AM transmitter in which a carrier is sent out for a 1 and no carrier for a 0, which is the normal way they work, and send out a long string of zero bits. The receiver would pick up nothing at all and proabably just give random noise at it's output.

Brian.

 

[demetal]

Hi,

Actually I mean, About any method by which one can connect the UART directly to 433 module....will it work if Manchester coding is not used?

 

[marius810327]

Hi, You get modules that can be set up for different modulation schemes. Manchester is just another medium of transmitting, but it's not necessary and normal data packets can be transmitted. If the data that you transmit needs to be secured, implement a small encryption algorithm and its done.

Marius

 

[Vandal S]

If you only want to transmit 4 characters (like the commands for a toy car), I think you don't need the coding, you just have to choose from the ASCII table some characters with this characteristic (U for example is something like 01010101). I remember seeing even a calculation which told you how many characters are like this, but I don't remember where. And it would be useful for me, also.

 

[tpetar]

This can help You to analyze signals :