Manchester Code Library for Arduino

I made wireless motion dectors (see https://www.instructables.com/Wireless-PIR-Sensor... and I spent some time to search for a good library to avoid me to code too much.

I found some, and some have worked but when I opened the code, oh dear i has been flooded with a lot of blabla, multiples functions, Arduino stuff to be compatible with a lot of board...

So I decided to code a library myself, not the best, but the simpliest, readable and understandable.

https://github.com/mdeudon/Manchester.git

I won't explain the manchester code in details hereby, there is a lot of publication on internet that will do it better than me.

But just to resume :

A 0 bit is coded with a rising edge.

A 1 bit is coded with a falling edge.

This code is supposed to be more resistant to noise. That is why I've choosen it.

No ASK is not a bad word, it means : Amplitude Shift Keying.

And so what ?

It is a complicated acronym for something so simple :

• If I want to transmit 1, I emitt a signal.
• If I want to transmit 0, I stop to emitt the signal.

But before doing this, I need to tell to my receiver : hey it's me, I am about to send you a message !!

To do that, I will send it a suite of 1 0 1 0 1 0 ... the receiver will sense the signal, a regular signal : so it is not a noise but someting is talking to me, and measure the amplitude to make it a reference.

This is the purpose of the send_sync() in manchester_tx.h :

void Sender::send_sync()
/*send 32 HIGH LOW edges to synchronize with the receptor*/

{

/sending a sync signal

for (byte i=0;i<32;i++)

{

digitalWrite(RF_PIN,HIGH);

delayMicroseconds(T);

digitalWrite(RF_PIN,LOW);

delayMicroseconds(T); }

digitalWrite(RF_PIN,HIGH);

}

}

-> 32 is arbitrary, you can try to send less and see if it still works...

From then we can talk ...

To make understand the receiver we are sending data and not sync signal as in the previous step, let send a start byte.

Then the receiver will now that the following byte is the data.

void Sender::send_load(byte start[],boolean state)

-> call the function twice, one time to send the start byte and oner time to send the data byte

void Sender::send_byte(byte car)

-> use previous function to send start byte + data byte, this is the one you should use in your skectch

void Receiver::seek_start()

-> loop indefinitly until a start byte is received

This is a blocking function, I may improve it ...

byte Receiver::read_signal()

-> read a byte

This is also a blocking funciton, but there is a timeout, so if the signal is not received within few ms it returns 3

I count on you to buy a pair of RF emitter/receiver...

Plug the emitter data pin on pin 9 of an Arduino. The receiver is on pin 11 of a another Arduino.

Install my library and check the examples.