Home Automation – STOP PRESS!

Following trials today of the emonTH prototype (see previous post) it is clear that I have a lot of 433MHz traffic. This isn’t at all surprising as we have a lot of wireless devices including a Davies Weather Station which uses that frequency quite heavily. In fact, it was a close call to get 433MHz in the first place and I felt when I ordered that we should be going with 868MHz instead but thought I’d give 433MHz a try first.

RFM69CW 433/868MHz Transciever Board from HopeRF
RFM69CW 433/868MHz Transciever Board from HopeRF

It didn’t work out. The emonTH prototype is sending the data every minute but the emonBase is only seeing about 1 in 3 of the packets sent. Investigation with minicom revealed that the frequency is busy and I suspect that the lost packets is due to packets clashing. The thing is that the RFM69CW does not check that the channel is clear before sending and it does not request an acknowledgement so it never knows if there was a clash and the data lost so it just goes back to sleep and sends the next packet a minute later.

So I have decided to switch to 868MHz before I go any further. The 433MHz devices will be used for collecting data from other 433MHz devices that we have or get in the future but all of the future Open Energy Monitor devices will now be 868MHz.

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