#Raspberry pi modbus server serial
#Raspberry pi modbus server trial
#Raspberry pi modbus server plus

The main file would write (and overwrite) a single line in the modbus.csv file. This same setup was used for the system log, data logging, and output to the Modbus TCP script. If a new file is needed or the datafile is a single line that gets written over, the “a” would change to a “w”. The file write would look a little different depending on if writing to the data log file or the system message file (as is shown here).

#Raspberry pi modbus server plus

# Print to a CSV for recording data or system info # file = open(“/media/pi/USB_Drive_Name/file location if desired/filename.csv”, “a”) file.write(“Message to write to file”+” ”) #file write of message plus a carriage return file.flush() #clear writing cache file.close() #close file The “a” option at the end of the command line specifies the file will be opened and entries will be appended at the end of the file. With some simple examples and tutorials online and even YouTube, the format was somewhat simple and straightforward.

#Raspberry pi modbus server trial

They then remained off for the remainder of the trial (22 hours).Ĭreating the CSV file (for data logging) was just as simple to implement as other components of this system. The ambient temperature was even low enough on the factory floor to keep the processor temp down and the fans only turned on and off a couple times to start. When analyzing the captured data file, it went very smooth. Then a final overnight test was run with the #1 prototype. The field test went smoothly with both prototypes for a good three-hour run.

With an additional fan and some vent holes made in the enclosure necessary for needed air flow and reducing backpressure, both prototype systems were able to run for many hours (full workdays on several instances) at my desk. It worked just as I had hoped and would be easily setup even by the greenest of coders. I utilized the autostart file setup (/home/pi/.config/autostart) I found while researching the best way to start up a script automatically on Pi boot up. I decided it was best to break up the main script file as well as the others for them to operate asynchronously. The final script configuration utilized 4 script files (Modbus TCP used in Comms script, Data Logging, System Operations, and a MQTT connection script for the URL dashboard connection) that all started on power up. From there, it is some simple connection open and monitoring commands in partnership with the connection write or read commands. For the two prototypes discussed here, there are pyModbusTCP API and Modbusclient declarations that are declared in the setup portion of the script. These registers are then transmitted internally to tags or data registers determined by the manufacturer but are still within industry standards. With Modbus, you read and write from holding registers. One author refers to it as the “grandfather of modern fieldbus,” and states that it is still doing the job after four decades. With industrial equipment made by OEMs such as Keyence (i.e., camera controllers) and Mitsubishi (PLCs, VFDs, and HMIs), it can be referred to as ModTCP or Modbus TCP. For this application, and a growing use of it these days, it can be implemented over ethernet. It is a master/Slave protocol that can be handled by wiring from device to device with the typical transmit and receive wiring of a 9-pin d-sub connector or sometimes with two-wires daisy-chained between screw terminals.

#Raspberry pi modbus server serial

Modbus is a serial fieldbus communications protocol. The scope of this project called for data not only saved to the attached USB drive (easily configured to a network drive if desired), but also to communicate specific data to a web-based dashboard (used Adafruit IO) and locally to an industrial controller (PLC) or display via Modbus TCP. But the system needed more functionality than just the internal components. With separate script files all able to run the individual components (including the two fans), it was relatively easy to merge them all into one main script file.

Industrial Raspberry Pi Project, Part 3.

Industrial Raspberry Pi Project, Part 2.

Industrial Raspberry Pi Project, Part 1.

My last post left off just short of how the script files were implemented and/or tied together to complete the system… so here we go.