RF Door/Windows Alarm Sensor PC Interface

[hedehede81]

Hello everyone,

I have a home alarm system at home (cheap 315mhz wireless door alarm sensors and base unit, Chinese made). I would like to make USB RF PC interface. I ordered 315mhz RF receiver/transmitter kit
similar to described here: https://www.buildcircuit.com/how-to-use-rf-module-with-arduino/
and USB to RS232 TTL adapter for my PC, similar to this: **broken link removed**

Both receiver and transmitter needs 4 lines, VCC, GND, DATA and Antenna. VCC, GND and Antenna are all easy to take care of. Do you think such a config is possible:
PC Serial USB RXD -> Receiver Data line
PC Serial USB TXD -> Transmitter Data line

What I would like to is, triggering sensors (door, window, PIR etc) and capture this serial data in PC. Also triggering remote control buttons, recording events again, and later use these to disarm/arm the unit through PC. I'm not interested in protocol, decoding etc, all I would like to do is record some kind of repeatable input (and I know these cheap systems repeat the same signal always) and repeat it through PC Serial Port plugin.

do you think this is possible with only the hardware I mentioned? Would I need any middle man etc? Thanks a lot for any comments and thoughts in advance.

 

[shahbaz.ele]

dear it look good as you described, but when you go for hardware many things apear there.
to me it looks fine.
just try it, then report the problems

 

[hedehede81]

OK, I have received the RF transmitter and receiver kit, and connected to USB UART as previously described. I have succeeded capturing the data from door/window sensor, all they do is transmit 5 byte data many times when triggered. Maybe they transmit more data, but this is the part that is repeated, and it is enough for the PC part to look for. I can monitor COM Port in PC and when this byte sequence is received I can know which sensor is triggered. The problem remains in simulating the remote control of the Alarm. I can capture the data like the receiver(the repeating 5 or 6 bytes). However when replaying through the transmitter, nothing happens. I don't know if the whole data is only the repeating part or more, also I don't know if my COM port settings are correct.

Here is how my hardware is connected, USB UART is connected to PC. It has 4 pins: RX,TX,VCC (5V), GND. RF Link receiver has 3 pins, VCC(->UART VCC), GND(->UART GND), DATA(UART->RX). RF Link Transmitter has 3 pins, VCC(->UART VCC),GND(->UART GND), DATA(UART->TX)

Datasheet of transmitter suggests 12v, so I also tried putting 12V between VCC and GND pins with a power adapter. (also shorted GND with UART GND to have common ground level) again, nothing happens.

One more thing amazes me is that, if I keep only receiver connected to UART, and trigger sensors, I receive different byte sequences than if also transmitter is connected. And if I supply 12V to transmitter with adapter and only share ground with UART and receiver, the received byte sequences are different again. But since I connect first, learn what to look for byte sequences, then put these values into PC code, understanding when a sensor is triggered is easy, just different for different setups, nothing standard. Also, when receiving, I use 1200 Baud Rate, no parity, 8 data bits, but if I use 1200 Baud Rate, odd parity, 7 data bits, byte sequence is completely different. So this is the problem, I don't know the port settings, I don't know what to transmit.

I suspect that since I don't know actual baud rate, stop bits, data bits etc, I can get away with the receiver part, since I already learnt what to look for before. But I don't know what connection settings and byte sequence looks in the receiver of the home alarm. Is there any way I can know the correct settings and find the correct bytes to transmit?

Initially I thought that since this is serial communication (only 1 and 0) even if I use different COM settings I would still be transmitting same 1s and 0s, only interpreted differently in the receiver part. I guess I'm wrong in that? Can you please help me how to capture the remote control correctly and transmit through my RF link?