madrian
Posts: 29
Joined: Tue Aug 28, 2012 6:48 pm

Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 5:45 pm

Hi,

I am trying to setup a RXB6 433Mhz receiver.

At this moment I am able to receive commands from my wireless electric socket remote control (433Mhz) with RFSniffer (433Utils). So, the receiver is working.

I have two different type 433Mhz weather sensor, but I am unable to read any data from it (RFSniffer, temperature app). Is there nyone who has read successfully data from these cheap sensors?

Images:

http://hopp.mihalko.eu/1PARVhV
http://hopp.mihalko.eu/1PARXX1
http://hopp.mihalko.eu/1ZQxwVx

https://github.com/martinlipovsky/raspb ... er-station

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joan
Posts: 14762
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 6:51 pm

Put a digital scope on the receiver GPIO and see if there is an obvious signal.

My piscope should show the signal if you don't have a scope.

madrian
Posts: 29
Joined: Tue Aug 28, 2012 6:48 pm

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 8:15 pm

Piscope:

433Mhz controller - RFSniffer see this:
https://www.youtube.com/watch?v=6hICuW-f2Hs

Weather Sensor:
https://www.youtube.com/watch?v=BnQZY_qk7gw

If I am not wrong weather data is transmitted every min, on the video at 1:17min.

Can we do anything with this?

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joan
Posts: 14762
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 8:19 pm

Possibly, but you need to zoom in to see the message detail. Use the down cursor key to zoom-in and the up cursor key to zoom out. You probably want to be looking at 50 milliseconds or so on the screen.

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joan
Posts: 14762
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 8:23 pm

A tip, a lot of that may be radio static which you can filter out. WIth nothing being transmitted see how much signal is picked up. Use the command pigs fg 27 100 to remove all edges shorter than 100 µs (pigs fg 27 0 to disable filtering).

madrian
Posts: 29
Joined: Tue Aug 28, 2012 6:48 pm

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 8:38 pm

I think there is still too much noise?

http://hopp.mihalko.eu/1nlZSKR

(pigs fg 27 100 enabled)

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joan
Posts: 14762
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Tue Jan 26, 2016 8:48 pm

You could try higher, say 200, but once the signal is present the noise threshold will be raised anyhow.

I'd try at 200 and then transmit and capture the signal.

madrian
Posts: 29
Joined: Tue Aug 28, 2012 6:48 pm

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Fri Sep 02, 2016 4:37 pm

Finally I have more time to play with this setup.

I am following this guide:

http://rayshobby.net/reverse-engineer-w ... rs-part-1/

I did my best, but am unable to receive any data with the program for RPi.

The receiver/transmitter is working, because I am able to receive/send signal with 433Utils (RFSniffer) from my ON/OFF RF switch.

Let's move on my Weather Sensor:

I build a sniffer from a cheap USB sound card + RXB6 receiver, here is the result:

https://f001.backblazeb2.com/file/mihal ... sensor.wav

If am not wrong, I red these values from Audacity:

sync_length (selection start)20223-19823(selection end) = 400 / 44.1 = 9.07ms
0 (or 1?) 20337-20255 = 82 / 44.1 = 1.85ms
1 (or 0?) 20528-20360 = 168 / 44.1 = 3.80ms
sep length 20359-20335 = 24 / 44.1 = 0.54ms

First, I tried the default values in the program, where are nearly same values: not working.

Then, I modified the values to:
#define RING_BUFFER_SIZE 256
#define SYNC_LENGTH 9000
#define SEP_LENGTH 500
#define BIT0_LENGTH 3800
#define BIT1_LENGTH 1850
Still nothing.

Then I fired up my RTL SDR device and rtl_433 utils, with this, I am able to receive and decode signal. The sensor is recognized as a prologue sensor, here is the source of this module:

https://github.com/merbanan/rtl_433/blo ... prologue.c

From the description in the code:
the sensor sends 36 bits 7 times, before the first packet there is a sync pulse
the packets are ppm modulated (distance coding) with a pulse of ~500 us
followed by a short gap of ~2000 us for a 0 bit or a long ~4000 us gap for a
1 bit, the sync gap is ~9000 us.
…so I am working with correct values.

But then why I am unable to receive anything without RTL SDR?

Thank you,
Adrian

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Ronaldlees
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Location: North Carolina, US
Contact: Website

Re: Weather sensor + RXB6 433Mhz Superheterodyne receiver

Fri Sep 02, 2016 7:12 pm

joan wrote:Put a digital scope on the receiver GPIO and see if there is an obvious signal.

My piscope should show the signal if you don't have a scope.
I eavesdropped on the thread and after reading your suggestion, decided to try the piscope. It's actually a practical tool. It really is. Even if you already have a fancy hardware scope and probes, it's sooooo much easier to use piscope for a quick look, and not have to remove the cover of the enclosure.

Now I know where your avatar comes from :-)
I am the Umbrella man

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