Creation of a PDF report with Python

I was asked quite frequently how a PDF report with process data from the PLC program can be created with PLCnext. An easy way is to use a Python script which collects process data via the REST API and creates the PDF on the device. The creation of the script is triggered by a function block in IEC61131 on the PLC.

Here are the necessary steps:

1. Install pip on the PLC for the user "plcnext_firmware". This is the user which is used by the function block that executes the Python.

    sudo passwd plcnext_firmware --> assign a new password
   
    su plcnext_firmware
   
    curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
   
    python3 get-pip.py
   

2. Install the required Python libraries:

python3 -m pip install requests

python3 -m pip install fpdf

3. Create a Python script and copy it to the /opt/plcnext/ folder on the PLC:

	import requests
	import json
	import sys
	from fpdf import FPDF
	from datetime import datetime

	sys.path.append('/opt/plcnext/.local/python3.10/site-packages/')

	class PDF(FPDF):
			def header(self):
					self.image('Logo.png', 10, 8, 40) # optional
					self.set_font('Arial', 'B', 20)
					self.cell(0,10,'Monthly report', border=False, ln=True, align='C')
					self.ln(20)

			def footer(self):
					self.set_y(-15) 
					self.set_font('Arial', 'I', 12)
					self.cell(0,10,f'Page {self.page_no()}/{{nb}}',align='C')



	##################################
	 Read data from the PLC via REST
	##################################
	response = requests.get('https://192.168.178.10/_pxc_api/api/variables?paths=Arp.Plc.Eclr/INST_SolarEnergy.diPower', verify=False)
	data = response.json()

	variables = data['variables']
	value = variables[0]['value']

	###############
	Timestamp  
	###############
	now = datetime.now()
	current_time = now.strftime("%m.%d.%Y %H:%M:%S")

	################
	Create PDF   
	################

	pdf = PDF('P','mm','A4')

	pdf.alias_nb_pages()

	pdf.set_auto_page_break(auto=True, margin = 15)

	pdf.add_page()

	pdf.set_font('Arial', '', 12)

	mes = 'The power of the pump is ' + str(value) + ' W'

	pdf.cell(200, 10, 'Report '+current_time, ln=True) 
	pdf.cell(200, 10, txt = mes, ln=True) 

	pdf.output('Report.pdf')

4. Create a new PLC project.

5. In the project create a variable which can be accessed via the REST API. For local variables, the "HMI" tag must be selected.

6. Import the PLCnextBase library into the project. The library is available in the PLCnext Store.

7. Create a program which uses the PBCL_LinuxShell command to execute the Python script. Be aware that the PLC will perform a warmstart after the first execution of the FB.

8. Download and start the program. The script is executed via the xExecuteScript variable. The pdf report is stored in the /opt/plcnext/ folder. The local variable xRetain must have the retain tag checked.