I'm having trouble getting a reliable one wire network up and running on my raspberry pi and would appreciate any help.
I have 8 x DS18B20 temperature sensors installed at various points in my house. The sensors are connected back to a central location using cat5 cable. There are 4 lengths of cat5 cable between 5-15m long. Each cable has two sensors wired like this:
Orange - Vcc
White/Orange - Gnd
Brown - Data sensor 1
White/Brown - Not connected
Blue - Vcc
White/Blue - Gnd
Green - Data sensor 2
White/Green - Not connected
As I installed each sensor I tested it and they all worked correctly however when I connect all 8 sensors together (in a star configuration) no sensors are detected. When I add sensors one by one I can get about 4 sensors working together before the interface stops working. Doesn't matter which sensors I add and in which order it will always fail once I get to the fifth sensor. I am assuming that with more than 4 sensors connected there is too much interference/echoes on the network. I have also learned that the star configuration is the worst topology to use and that I probably should have put the data and gnd in the same twisted pair.
Does anyone have any what I can do other than rewiring the network, which will take me 2 days
I was thinking of the following options.
1. Add an additional one wire bus on the pi so I have 4 sensors on each bus.
2. Multiplexing so I can read 4 sensors then switch the data line to read the other 4.