Sunday 25 September 2016

Obtaining and deciphering radio messages

Aim: to obtain and decipher radio messages from household devices.

Test device: Clas Ohlson (WS2015) temperature sensor - typical household 433MHz device.

Receiver: USB dongle (e.g. hsy® USB 2.0 Digital-DVB-T-DAB FM RTL2832U FC0013B SDR TV Radio Receiver-Stick) on a Windows laptop.

Data study and capture: SDR# (SDR sharp), 8bit wave file made of a couple of seconds and filesize of a few megabytes.

Understanding the data: each clock-cycle has a level shift (0/1). Logic1 has a level shift within a clock cycle, whilst logic0 does not. Bits 21-35 are temperature (scaled as +50 x 128). Useful website was

Data processing: done 'myself' in Octave -- the key command was wavread('FILENAME.wav'). But also some 'debouncing' was done to infill the many dropped "1" values. Plus all of the 6 messages were taken (2 channels, 3 messages per channel) after some synchronizing.

Software, SDR#:

Software, Octave:
Each minute 3 near-identical 36-bit messages sent:
Example, zoom in on first 5 bits of first message (notice the many 'dropped' "1" values): 
After tidying and then converting the binary message to a normal (decimal) value the result is found: 

See also Part 2

Tuesday 13 September 2016

Winter wonderland

All winters are cold and snowy in Finland, but some much more than others.

Weather station at Helsinki Airport in Vantaa.
"Cold days" are with maximum temperature below 0C.
"Snow days" are simply days with at least some snow on the ground.
Winters are shown such that e.g. "2010" on the graph means the winter of 2009/10 (e.g. November 2009 --  April 2010).

Source: Finnish Meteorological Institute.

Summer days

I had the impression that this year had lovely summery weather. it did, and I enjoyed it lots. But apparently it was only about the same as the long-term (30-yr) average (of about 50 days per year), and even this year was cooler than some of the recent warmer summers that Helsinki's had in the last decade or so.
Weather station at Helsinki Airport in Vantaa.
"BBQ days" are with maximum temperature above 18C, at least 4 hours of sunshine and no rain.
"Hot days" are with maximum temperature above 25C.

Source: Finnish Meteorological Institute.