Posted on November 28, 2017 at 00:38In the old days, sometime after they invented wires.
They made a simple diode and that lead to a multi-drop technology, originally called DTL logic
that is used in 100% of all electronic equipment ever.
simplistically, with a voltage and pull up resistor connected to 1000 diodes, through any one diode, you can pull to ground.
simplistically, any processor Tx Pin can pull a diode circuit and every other processor can listen. everyprocessor is listening to a single channel ( a wire with diodes)
that is multidrop communications
RS232 is a point to point technology not suitable for multidrop at a distance.(although in half duplex it can be done with a diode as discussed upto a Meter)
but usual multidrop comms is usually done with these,
RS485 is almost identical to CanBus on the wire, both use the multidrop diode method somehow.
I'd recommend: CanBus is an extremely fast, anti-collision system that seems bulletproof under 1 km.
Distance and Bandwidth requirements determine the cable/radio requirements
LoRa radio seems the next level for a few kms. (upto 5 km line of sight. refer to Clive's work
https://community.st.com/community/stm32-community/blog/2017/04/05/lora-discovery-kit
)
