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I am developing an industrial sensor using a sensor IC and an ARM MCU which communicate via I2C. The data size is 3 bytes. Because the environment in which the sensor is located is harsh ( high temperature and high humidity ) the sensor has a watertight enclosure, and I can't afford to have more than 1 cable coming out of it.

I want to offer the possibility of connecting the sensor to a PLC, PC and to a custom LCD display at the same time. It doesn't need to be real time. I am considering building a communication module that has an integrated LCD screen and who can pass the data to a PLC and a PC. For the PC communication, I will use USB, but for the PLC, I'm not very sure. What is a common serial protocol that most PLCs have which doesn't an expansion module for the PLC? Thank you.

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    \$\begingroup\$ RS485 is failrly common, as are MODBus and CAN Bus. \$\endgroup\$ Sep 30, 2019 at 0:41
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    \$\begingroup\$ I can't afford to have more than 1 cable coming out of it. Funny enough, there is a serial interface called "1-Wire" that, you guessed it, only has one wire to interface from master to slave. \$\endgroup\$
    – user103380
    Sep 30, 2019 at 0:43
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    \$\begingroup\$ I bet LoRaWAN (an RF protocol) would do pretty well in a noisy environment because it's spread-spectrum and uses "chirp" modulation. It's well suited to small payloads and long range. No wires required. \$\endgroup\$
    – vicatcu
    Sep 30, 2019 at 1:10
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    \$\begingroup\$ Have you ever thought about IO-Link? \$\endgroup\$
    – Mike
    Sep 30, 2019 at 5:48
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    \$\begingroup\$ @CalebReister, 1-wire was designed to use 1 wire and be rugged. Not to be ultra-low power as it uses open-drain and pull-up resistors. It's low speed (16 kbps) but not 'extremely slow', so may be good for 3 byte sensor packets. It'll go up 100 m of cable to bus-powered devices with a pull-up resistor, much longer with active pull-up assistance. \$\endgroup\$
    – TonyM
    Sep 30, 2019 at 6:21

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As a controls engineer in the automated assembly business, I recommend IO-Link. It's had an explosion of popularity in recent years and is still growing.

The data size is 3 bytes.

IO-Link supports up to 32 bytes (bi-directional)

Because the environment in which the sensor is located is harsh ( high temperature and high humidity ) the sensor has a watertight enclosure, and I can't afford to have more than 1 cable coming out of it.

IO-Link uses industry standard (usually M12) cables and field wireables which are available with high protection ratings. It can provide power and data transfer on as few as three wires in a single cable.

I want to offer the possibility of connecting the sensor to a PLC, PC ... at the same time.

This is what IO-Link was built for. A number of manufacturers (Balluff, IFM, Phoenix Contact, and Turk to name a few) provide IO-Link masters that handle the connection to industrial networks. This allows a PLC and PC to communicate with your sensor at the same time.

The communication can occur in real time so a connected PLC can make instant decisions and even send commands to the sensor.

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