433 Mhz Remote Control - Home Automation

Intro

TBD - How to setup the Raspberry Pi to run Python apps.

Use Case - 3T Motors

The use case described here refers to controlling blinds motors from 3T-Motors controlled by the 3T Mini-Funk-Empfänger MFE (3T Motors Mini Receiver). Unfortunately, there is little info on the web how to control these motors with a Raspberry Pi, so I had to do a little bit of work myself, and this work I'd like to share with you. The info here is probably applicable also for other devices, but also there: Be ready for a bit of work :).
First of all: For my case, such tutorials do not unfortunately work. So don't worry if they do not work for you either; Although the receiver module might perfectly work (as hardware), the receive.py code will not display anything, probably because the received protocol is unknown.
And this is the case where a tutorial like Super Simple Raspberry Pi 433MHz Home Automation from george7378 will save you / me. I mean, really: Without that tutorial I'd probably have been unable to achieve what I wanted, and I'm afraid: you too. Hence, a BIG THANK YOU to george7378 for sharing his knowledge with us.

Hardware Setup

There's nothing to add to the mentioned tutorial: Super Simple Raspberry Pi 433MHz Home Automation, except for: as it was not clear in the referenced tutorial Super Simple Raspberry Pi 433MHz Home Automation, I connected the modules like in this tutorial.

As such - taking into account that GPIO is set on GPIO.BCM mode - using the pinouts map from here, I found out that my receiver is on pin 27 and transmitter on 17.
As I worked with a "software first" mindset ;) I didn't solder any antena in the first phase and I thus had to stay (quite) close with the PI and the 433Mhz modules to both the remote control, as well as to the blind's receiver.

Software

Although I got the OK from the author of Super Simple Raspberry Pi 433MHz Home Automation to extend his code / publish the updated version, I don't know exactly which are the rights around the code posted on www.instructables.com so I'll refrain posting here the entire updated code; Instead I'll show you the delta.

There are 2 important changes I had to do:

• I have no computer monitor around, so I work with my Raspberry Pi as headless system with SSH from my Mac. Hence: no chance to display and chart like in the receiver code.
• For this project I used a Raspberry Pi 2.0 which not fast enough to record the received values in very narrow steps and thus the time estimation around how long the short_delay and long_delay should be in the sender is extremely inaccurate.

Receiver

For the receiver, only 1 second recording the values is enough. Thus: MAX_DURATION = 1.
I commented out all the print statements and all the code around pyplot.
I added a print('Time,Bit') before the for-loop and inside the loop a print(str(RECEIVED_SIGNAL[0][i]) + ',' + str(RECEIVED_SIGNAL[1][i])) after calculating the value of RECEIVED_SIGNAL[0][i].
I start the program with python3 ReceiveRF.py > a.csv and right after the program starts I make sure to push the appropriate button on the remote and keep pushed till the program finishes (1 second later).
I extract the a.csv file from the Pi via: scp <pi_user>@<pi_hostname>:/home/<pi_user>/a.csv ./a.csv In order to visualize the CSV file, I use the wonderful online chart creator from datawrapper.de.
I try to identify in the chart 1-2 blocks of signal without errors, and I write down the associated code, as explained in the referenced tutorial. For example, I identified a code like 1110001110101100111100001011000011.
Hints:

• validate with several signal blocks if you got the right code
• repeat the process and record once more the same button on the remote. Make sure it's the same code. If so, perfect: continue. Else, sorry for you, I have no idea how to proceed, as you might have a system with rolling code.

Transmitter

As we hopefully somehow got the right code, we must find out another very important piece of info: How long is the "long signal" and how long is the "short signal". Based on the CSV file above, try to calculate on more places, the duration of a long 1 / long 0 or a short 1 / short 0. Make sure you check in the noise-free blocks you worked with in the steps above, to make sure you don't get wrong numbers. It does not matter if it's 0 or 1; It only matters if "long" or "short" but checking them for both 0 or 1 gives you a better feeling about the numbers.
Because this is the point with the second challange: I - at least - never been able to get closely similar numbers here.
I thus had to try to test with various numbers till I identified the right durations, and here is what I did in a copy of TransmitRF.py:

• identify reasonable lowest numbers for short_delay and long_delay (based on the observations above) and set them as the appropriate values.
• take a reasonably high NUM_ATTEMPTS, e.g. 100
• take a bit longer extended_delay = 0.03 just to be sure that the receiver is always ready to receive the next block.
• in the for-loop on the first position, for each t calculate something like:

sd=short_delay + 0.000002 * t
ld=long_delay + 0.000002 * t * 2
print (str(t) + ' ' + ' ' + str(sd) + ' ' + str(ld))

And then use sd instead of short_delay and ld instead of long_delay in the code below (each of them appears twice in the code!!).
This adjusted copy of TransmitRF.py will now attempt to send the code identified in the chapter above with continuously increasing duration for the short_delay and long_delay. In the moment the transmiter sent the code with the duration expected by the receiver, the receiver will "do something" In my case, the blinds will start moving downwards. This is the moment you have to notice the right t when the receiver accepted the transmitted code, and based on this you can calculate the right short_delay and long_delay which you then can use without problems in the original TransmitRF.py file .

Conclusion

Great tutorial Super Simple Raspberry Pi 433MHz Home Automation which I had to slightly adjust:

• for hardware setup I used the guide from RF 433 MHZ (Raspberry Pi); As result, my receiver worked on pin 27 and transmitter on 17
• using a headless PI, I had to export the received data as CSV and draw the charts with an online service
• I had to play a bit try/catch with the transmission time for the long and the short blocks, in order to find the right numbers