Proposed master, multiple slave sensor system

Thread Starter

AlbertHall

Joined Jun 4, 2014
12,396
I need a system to receive signals from multiple sensors back to a central point. The cable length will be up to 4 meters and there will be some interference around (low voltage motors and solenoids). I looked at RS485 but it seems very complicated for what I need. The master could poll each sensor to request the latest data.

I came up with this idea. Use RS485 interface chips (MAX485?) and twisted pair cable to connect everything together. Use a PIC USART to transmit the required sensor address. The addressed sensor then transmits its data while all others ignore it. I could use the ninth data bit from the USART to identify when a sensor address is being transmitted.

Does this seem to be a viable system?
 

nsaspook

Joined Aug 27, 2009
13,555
I need a system to receive signals from multiple sensors back to a central point. The cable length will be up to 4 meters and there will be some interference around (low voltage motors and solenoids). I looked at RS485 but it seems very complicated for what I need. The master could poll each sensor to request the latest data.

I came up with this idea. Use RS485 interface chips (MAX485?) and twisted pair cable to connect everything together. Use a PIC USART to transmit the required sensor address. The addressed sensor then transmits its data while all others ignore it. I could use the ninth data bit from the USART to identify when a sensor address is being transmitted.

Does this seem to be a viable system?
Be sure to not confuse the physical interface with the data communication protocol. Something like modbus is a communications protocol that can operate on many physical interfaces. Sure, simple 9 bit uart mode node addresses can easily be used to make a master/slave communications protocol that can use the RS485 physical interface for speed, noise immunity and multiple drop node compatibility. It's pretty much the default hardware capability for most controllers

https://community.silabs.com/s/article/uart-using-9-bit-mode-of-the-uart?language=en_US
 
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