This library can be used to send an received code to/from a SELECT PLUS Wireless Doorbell. In the Netherlands these where sold at the Action store (jan 2015). Perhaps they are also sold at other stores using a different brand name.
To identify if your unit is compatible with this library; the transmitter PCB is labled with: QH-C-CE-3V Rev1.0 Quhwa and the main IC has type number: MC908T 1439N. The receiver PCB is labled with: QH-832AC Rev1.0 Quhwa and has two IC's: TR1834B and TX102R. All of these IC are undocumented, at least I couldn't find any documentation.
The transmitter uses simple OOK/ASK modulation sheme. As far as I understand this, this just means that the transmitter is just turned ON and OFF. When the transmitter is ON it will transmit a 433 MHz signal and when it's OFF, nothing will be transmitted.
I only tested this library with a single wireless doorbell, so it could well be possible that other doorbells uses other codes.
This is how the signal looks like:
__ ______ ______ __ ______ __
| |____________________________| |__| |______| |__| |______| |
______ __ __ __ __ ______ ______ ______
__| |______| |______| |______| |______| |__| |__| |__| |
______ ______ ______ ______ ______
__| |__| |__| |__| |__| |
One way to look at the above signal is to use 4 different bits and a sync signal:
__
| |____________________________ : SYNC
______
| |__ : LONG - SHORT = 'X'
______
| |______ : LONG - LONG = '1'
__
| |__ : SHORT - SHORT = '0'
__
| |______ : SHORT - LONG = 'F'
Using the above scheme, the code my wireless doorbell transmitter is sending is: X10101FFF0XXXXXXXX
But it makes more sense to inverse the received signal, since then we only need 2 bits:
____________________________ __ ______ __ ______
__| |______| |______| |__| |______| |__
__ ______ ______ ______ ______ __ __ __
| |______| |__| |__| |__| |__| |______| |______| |______
__ __ __ __ __
| |______| |______| |______| |______| |______
____________________________
__| |______ : SYNC
__
| |______ : SHORT - LONG = '0'
______
| |__ : LONG - SHORT = '1'
Using the above improved scheme, the code my wireless doorbell transmitter is sending is: 0 1010 1111 0000 0000 (decimal: 44800)
Since the whole code is based on edge detection we actualy don't have to inverse the signal anyway.
The most important part of encoding/decoding the signal is timing. I have found the following timing:
period: ~1500 us short: ~375 us (1/4 of period) long: ~1125 us (3/4 of period) sync low: ~5800 us ( 4 * period - 1/8 * period )
To use the library, you have to download the files and add them to your arduino libraries folder.
The library consist of two classes, a receiver (DoorBellReceiver) and a transmitter class (DoorBellTransmitter). You can use either one or both in a sketch. The default pins are:
Receiver RX: PIN 2 (arduino interrupt 0) Transmitter TX: PIN 11
You could change the pins, by calling the constructors with different arguments.
A simple example could look like this:
#include <DoorBellReceiver.h>
void setup() {
Serial.begin(9600);
DoorBellReceiver doorbellReceiver(0, 1, myCallBack);
}
void loop(){}
void myCallBack(unsigned int code) {
// Print received code
Serial.print(F("Received code: "));
Serial.println(code);
}A simple example could look like this:
#include <DoorBellTransmitter.h>
DoorBellTransmitter bell;
void setup(){
Serial.begin(9600);
bell.printConfig();
}
void loop(){
char buffer[7];
if (Serial.available() > 5) {
Serial.readBytes(buffer,6);
if ( (buffer[0] == 'r') && (buffer[1] == 'i') && (buffer[2] == 'n') && (buffer[3] == 'g') ) {
Serial.println("Ringing door bell");
bell.ring();
} else {
Serial.println("Unknown command");
}
}
}