arduino FINALLY GOT Multiple ARDUINO SLAVES WORKING WITH MAX485 two wire MODBUS RTU

[4felo]

Finally got multiple arduino slaves being monitored and controlled by Daqfactory. I've been working on this for the past 2 weeks and found no documentation available. I'm able to read analog inputs registers, write to and monitor PWMs registers, read & write to digital pin registers. Communication is through two wire modbus RTU. It's simply fascinating, i can literally monitor an control any of my inputs/outs in real time using  cheap arduino unos. Stuff that is done by some really expensive PLCs out there. I'm still making some documentation, but if any of you need assistance post in the forum.

[AzeoTech]

I'm assuming the no documentation comment is about the Arduino side?

[svego]

please share arduino code with others...what board did you use ?

[4felo]

Sorry it took long, forgot about it. 

arduino code and daqfactory sample program are attached bellow. Just follow the Readme.txt

 

MAX485_TO_arduino_TO_DAQfactory.rar

(Works with MAX 485 and arduino Uno)

1. Download Daq Factory Express and load the DAQFactory Document.

2. Load "SimpleModbs_DEMO' to the arduino, make sure to check for slave ID.

3. Double check the configuration settings in Daq factory. Especially the ***PORT NUMBER.***

There are multiple working libraries for implementing modbusRTU on arduino.

1.  ModbusMaster ----- Works with only one slave and Master, modification may be needed to implement multiple nodes.
http://playground.arduino.cc/Code/ModbusMaster

2.SimpleModbus (current)

3. Modbusino---- Modification of the simpleModbus Lib
https://github.com/stephane/modbusino

4. Modbus-Master-Slave-for-Arduino ---- Single library that contains code for both master and slave.
https://github.com/smarmengol/Modbus-Master-Slave-for-Arduino
 

[Aditya]

can you please share circuit diagram for multiple slaves