Assuming I cannot use wireless technologies such as LoRa, LTE-M or SigFox in the environment for the install, I must use a wired sensor protocol to communicate with the gateway installed remotely in a building.
The cable runs can be up to 20m from the gateway and ideally I will be purchasing a reliable solution that is not overly expensive. It would be excellent if the sensor was CE compliant but there doesn't seem to be a low cost option (<£20), e.g. solar.
So, the requirements are:
- Can connect to 10 or more devices
- Maximum distance at least 20m
- Price less than £20 for temperature/ humidity/ lux (luminosity) sensor(s)
There are many options such as SPI, I2C, RS485, Onewire and CAN. The protocol we select will determine the sensor we select.
The Onewire protocol from Maxim (Dallas) looks ideal but there are as yet a limited range of sensors, (in saying this we could use the maxim bridge)
What is the best wired protocol for the requirements listed above?