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addressed output device

Posted: Fri Feb 28, 2020 6:32 pm
by adelspark
I've been long searching for a small device (chip or module) whereby I can have several of these devices wired together in a string so that when their input goes high, then they will send a output to an arduino with an address, so the arduino knows which one went high.
I was thinking something with an I2C or RS485 arrangement, where perhaps the arduino could poll each device and see if it had changed state since the last read, so that the arduino could output which device number(s) had changed state.
My typical application would be using a long 20m long 'rail' with a hall effect or reed switch as the input to each of these devices spread out along the rail, such that when a vehicle moved along the rail, the output from the devices (and hence from the arduino) would let me know roughly where the vehicle was located.
Since the rail could be 20m or longer, I want to minimize the number of cables to each device, hence my idea of a polling bus arrangement.
Does such a device already exist or has anyone else had a similar need?
Thanks in advance :D