433.py
A command line tool to record, plot and replay arbitrary digital 433MHz signals using a Raspberry Pi.
Using this tool, a Raspberry Pi and a set of cheap 433mhz receiver/sender modules you can work with 433MHz signals.
This allows to clone key fobs, garage door openers and remote controls that send data on 433MHz.
These types of devices typically send a static repeating code when their buttons are pressed.
Once you recorded a code with --record, you can view it using --plot and replay it with --send.
Similar tools for working with 433MHz signals often try to decode/encode the signals. In contrast, this tool simply records and replays the digital signals that are actually beeing sent. This allows this tool to work with arbitrary codes/devices as long as the used codes are static and the protocol is not interactive.
How to use it?
usage: 433.py [-h] (--record GPIO | --plot | --send GPIO) [--recordlen MS] FILE
positional arguments:
FILE the json file to load or store a signal
options:
-h, --help show this help message and exit
--record GPIO record a signal on gpio pin GPIO and store it in FILE
--plot plot the signal stored in FILE
--send GPIO replay the signal stored in FILE on gpio pin GPIO
--recordlen MS amount of milliseconds to record (defaults to 250ms)
Example
We are going to use the tool to clone the remote control of a set of remote-controlled power sockets like these.
Wiring
The receiver module is typically rectangular and should have 4 pins: VCC, DATA1, DATA2, GND. Connect VCC to the Pi's 3.3V output, GND to the Pi's GND and either DATA1 or DATA2 to one of the Pi's GPIO pins. Note the GPIO number (not the pin number) that you connected to DATA. The GPIO number depends on the specific board you are using. See the pigpio documentation for a board-dependant pin/gpio mapping.
The typically square sender module has only 3 pins: DATA, VCC, GND. Connect VCC to the Pi's 5V output, GND to the Pi's GND and DATA to another one of the Pi's GPIO pins. Note the GPIO number.
For our example, we are using a Raspberry Pi Zero W. We have connected the receiver module to GPIO 27 (= pin 13) and the sender to GPIO 23 (= pin 16).
Recording
Make sure the pigpio daemon is running on the Pi using sudo pigpiod. Hold down a button on the remote and run
./433.py --record 27 signal.json
to record 250ms of the remote's signal into the file signal.json. The length of the recording can be adjusted using --recordlen. After the recording, the tool prints the number of recorded signal change edges. This value can serve as a indicator if the recording was successfull. In case of the remote control used for this example, an amount of around 1200 edges/second were normal.
Plotting
If your Pi does not have a display, it is possible to do this step on another machine. Simply copy the recorded json file to another machine. Then run
./433.py --plot signal.json
to display the recorded signal in an interactive window using mathplotlib.
It is possible to zoom in on the graph and check if the recording was successful, how the signal is encoded and if it is actually repeating.
Replaying
To replay the signal stored in the file signal.json simply run
./433.py --send 23 signal.json
Range
Antennas can be added to extend the range of the cheap transmitter modules. A simple 17cm wire antenna worked well for me.