TINNYMODBUS (ModBus tiny multi-sensor module)

TinnyModBus is a very small 11x26mm 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.

Main specs

• Size is only 11x26 mm including screw sockets
• 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 2 USD

Wiring of TinnyModBus module

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

• multiple i2c & 1w sensors can be simultaneously wired

  >~~~~~~~~~~~~>---  GND   --->|-|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|SCK|>-----  SCK  ----> i2c/SCK sensor(s)
  >~~~ <1.2km ~>--- 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

ModBus detailed register description are in MODBUS.md.

Schematic, Printed Circuit Board, 3D layout are available on CircuitMaker, but can be also checked in docs folder.

Docs & usage scenario examples are in tools/examples/ folder.

BUILD

See tools/docker folder for easy build receipt.