Send RF 433MHz data to Domoticz RfxCom with protocol X10 from Arduino Nano

Question

I have installed Domoticz on Raspberry Pi and bought an RfxCom 433MHz emitter/receiver. It works well for example with Chacon DiO 54781 door sensor. I want to create my own sensor with Arduino that would be recognized by Domoticz as a native RF 433MHz device. In first place, I want to make a flooding sensor, I also need an On/Off information. I would like to implement X10 protocol because it seems to be the simplest one.

Answer 1

I finally found a documentation about RF X10 protocol: X10 RF Receiver.pdf

With following Hardware :

• Arduino Pro Mini 5V (4€) https://www.amazon.fr/gp/product/B00QPUEFNW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
• RF 433MHz emitter/receiver (3€) (Note: only the emitter is used) https://www.amazon.fr/HDigiWorld-metteur-cepteur-commande-Arduino/dp/B00JTQI39G/ref=sr_1_3?s=computers&ie=UTF8&qid=1470813610&sr=1-3&keywords=433
• 3 wires : VCC, GND, Signal (on Arduino pin 2)

I've created the following working code for Arduino Nano :

/*
* Custom sensor (base code)
*
* Emission in RF 433MHz with the X10 protocol for Domoticz
*
* Hardware :
* Arduino Pro Mini 5V (4€) https://www.amazon.fr/gp/product/B00QPUEFNW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
* RF 433MHz emitter/receiver (3€) https://www.amazon.fr/HDigiWorld-metteur-cepteur-commande-Arduino/dp/B00JTQI39G/ref=sr_1_3?s=computers&ie=UTF8&qid=1470813610&sr=1-3&keywords=433
* Note: only the emitter is used
* 3 wires : VCC, GND, Signal (on Arduino pin 2)
*
* Documentation found for RF X10: http://www.printcapture.com/files/X10_RF_Receiver.pdf
*
* Example of malformed data received in RfxMngr in mode "nodec" (before this code was correctly debugged) :
*
* Packettype = UNDECODED RF Message
* UNDECODED NEC:1C515C86F0 
*
*
* Correct data that is now receveived by RfxMngr with this program :
*
*------------------------------------------------
* Packettype = Lighting1
* subtype = X10
* Sequence nbr = 13
* housecode = D
* unitcode = 1
* Command = On
* Signal level = 7 -64dBm
*------------------------------------------------
* Packettype = Lighting1
* subtype = X10
* Sequence nbr = 14
* housecode = D
* unitcode = 1
* Command = Off
* Signal level = 7 -64dBm
*------------------------------------------------
*/
const int pin_emit = 2; // Signal pin for RF433 emitter
const int pin_led = 13; // Internal LED : it will be ON when the "On" command is sent in RF, and OFF the the "Off" command is sent (changed each 60s)
const unsigned int X10_A1_ON = 0x00; 
const unsigned int X10_A1_OFF = 0x20;
const unsigned int X10_address = 5; // this is Housecode. In my case 5 results in "D" house code
unsigned int X10_data = X10_A1_ON; // command. I have implemented only On/Off for unit code 1
void setup() {
 pinMode(pin_led, OUTPUT);
 pinMode(pin_emit, OUTPUT);
 digitalWrite(pin_emit, LOW);
}
/**
* Bit to 0 : 1.125ms between rising edges, so before next bit
*/
void X10_sendBit_zero()
{
 digitalWrite(pin_emit, HIGH);
 delayMicroseconds(555); // Arbitrary value: I took around 1.125ms divided by two for the "VCC" state.
 digitalWrite(pin_emit, LOW);
 delayMicroseconds(570); // Total 555+570 : 1125μs = 1.125ms
}
/**
* Bit à 1 : 2.25ms entre les "rising edges"
*/
void X10_sendBit_one()
{
 digitalWrite(pin_emit, HIGH);
 delayMicroseconds(555); // Arbitrary value: I took around 1.125ms divided by two for the "VCC" state.
 digitalWrite(pin_emit, LOW);
 delayMicroseconds(1695); // Total 555+1695 : 2250μs = 2.250ms
}
void X10_send8bits(unsigned int data)
{
 // - Send the 8 bits, and then the complementary of the 8 bits.
 // from documentation: "Within each byte, bit7 is received first and bit0 last"
 int mask = 0x80;
 for(int i = 0; i < 8; i++)
 {
 int bit = mask & data;
 if (bit == 0)
 X10_sendBit_zero(); 
 else
 X10_sendBit_one();
 mask = mask >> 1;
 }
}
/**
* Sending a byte consists of sending this byte, and then sending the opposite of the same byte.
* As we send the opposite as well as the data, the total duration is always the same : 8 * (1.125ms+2.250ms) = 8 * 3.375 = total of 27ms
*/
void X10_sendByte(unsigned int data)
{
 X10_send8bits(data);
 X10_send8bits(~data);
}
/**
* Send a complete X10 packet
*
* Total duration :
* (9ms + 4.5ms) + (27ms + 27ms) + 0.555ms + 40ms = 108.055 ms
* from doc: "It appears, from articles on the 'net, that other people have seen a range from 95 msec to 116 msec for various transmitters and that standard X-10 transceivers can tolerate timing variations of 30-35% from nominal."
*/
void X10_sendState_once(unsigned int data)
{
 // - Header
 digitalWrite(pin_emit, HIGH); // "Burst" de 9ms
 delayMicroseconds(9000);
 digitalWrite(pin_emit, LOW); // Silence de 4.5ms
 delayMicroseconds(4500);
 // - Data
 X10_sendByte(0x50); // - Address
 X10_sendByte(data); // - Data
 // - Send a last rising edge to validate last bit
 digitalWrite(pin_emit, HIGH);
 delayMicroseconds(555); // Arbitraty value (but always the same), for "VCC" state.
 // - Footer
 digitalWrite(pin_emit, LOW); // Silence de 40ms pour signifier la fin de l'émission
 delayMicroseconds(40000);
}
/**
* Send a complete packet multiple times (this X10 protocol has not ACK))
* From doc: "Most X-10 RF transmitters send a minimum of five copies of the code separated by 40 msec silences although some can send single bursts." 
*
* 5 times 108.055ms = 540.275 ms, half a second
*/
void X10_sendState(unsigned int data)
{
 // - "clean" to be sure to have a zero for the first rising edge on init
 digitalWrite(pin_emit, LOW);
 delay(1);
 // - Send 5 time complete packet
 for(int repeat=0 ; repeat<5 ; repeat++)
 X10_sendState_once(data);
}
void loop() {
 if(X10_data == X10_A1_ON)
 digitalWrite(pin_led, HIGH);
 else
 digitalWrite(pin_led, LOW);
 X10_sendState(X10_data);
 delay(60000); // 1 minute
 // - I change state each 60 seconds to see changes in Domoticz
 if(X10_data == X10_A1_ON)
 X10_data = X10_A1_OFF;
 else
 X10_data = X10_A1_ON;
}

By changing House code and data, it is now possible to create our own RF sensors.

• Elo: Just to say, since my previous answer, I concluded it was too much effort for each new sensor to find how to implement a new protocol. So I finally tried and adopted "MySensors", because I only need to feed it with payload.