weathermon

Raspberry Pi-based weather monitor for Ambient Weather F007-TH sensors.

Listens to RF signals from the F007-TH sensors using a 434MHz reciever, tracks weather data, and serves a weather site written in Flask. Also sold as TFA sensor 30.3208.02.

F007-TH Data Encoding Format

• RF communication at 434MHz

• Uses Manchester Encoding ( '1' represented by high --> low transition)

• bit time = 1ms

• 195 bit frame, 65 bit packet repeated 3 times

• frames sent every ~1 min (varies by channel)

  • Map of channel id to transmission interval: {1: 53s, 2: 57s, 3: 59s, 4: 61s, 5: 67s, 6: 71s, 7: 73s, 8: 79s}
  • Source: github.com/gr-ambient

• Packet Format

  • header: all 1s, with final 01 before data starts
  • 8 bit sensor ID: F007th = Ox45
  • 8 bit random ID: resets each time the battery is changed
  • 1 bit low battery indicator: 1 ==> low battery
  • 3 bit channel number: channel 1-8 represented as binary 0-7, selectable on F007th unit using dip switches on back
  • 12 bit temperature data:
    • To Farenheit: subtract 400 and divide by 10 e.g. 010001001011 => 1099, (1099-400) / 10 = 69.9F
    • To Celsius: subtract 720 and multiply by 0.0556 e.g. (1099 - 720) * 0.0556 = 21.1C
  • 8 bit humidity data: relative humidity as integer
  • 8 bit checksum: cracked by Ron (BaronVonSchnowzer on Arduino forum)
  • padding: some 0s to fill out packet

Sample Data:

0        1        2        3        4        5        6        7
FD       45       4F       04       4B       0B       52       0
0   1    2   3    4   5    6   7    8   9    A   B    C   D    E
11111101 01000101 01001111 00000100 01001011 00001011 01010010 0000
header   sensorid randomid BCh#temp_perature humidity checksum xxxx
                           ^ battery, channel number

Translates to: Channel 1 F007th sensor displaying 21.1 Centigrade and 11% RH