TinnyModBus reconfigurable atmel attiny85 mcu based micro-module that speaks modbus over rs485 two wires. It collects measurements locally from large variety of implemented sensors. It can be reprogrammed right on its own rs485 via it's own bootloader.

Can speak modbus with several sensors attached, uses a max487 to communicate Have it's own 500mA budget, ESD protected rs485 lines, and reverse-polarity protection Can read attached sensor data over 1wire, i2c, spi, but also could do gpio or adc Has its own bootloader that speaks modbus and can be reprogrammed right on rs485 wires Internal IC metrics like Vcc voltage and SOIC8 temperature are available It is designed to cost less than 4 USD

Use 4 wires (ideal twisted):

2x @ 12/24V remote power 2x @ A,B rs485

Connects sensors:

i2c (any from /devs drivers) 1wire (up to 32 18DS20 temperature sensors) or can do gpio or adc

~~ --- 12/24V --->|+|   TINNY MODULE   |DAT|>-----  DAT  ----> 1wire/DAT or i2c/SDA sensor(s)
~~~~~~~~~~~~>---   A    --->|A|                  |+5V|>-----  +5V  ----> 500mA max for sensors(s)
~~~~~~~~~~~~>---   B    --->|B|__________________|GND|>-----  GND  ----> ground