#Sps siemens step 7 code#

:='webHMIData'.webHMI_AI0_TempCels: is a tag name inside the PLC, and will be replaced by the web server with the current value when the HTML is rendered (requested by the client).

The first two lines are samples for awp-commands and tell the web server that these tags can be written by the user-defined application (through a http/s post, using a form or another client).

#Sps siemens step 7 code#

The following code snipped shows a simple user-defined page, which displays two temperature values and the current states of digital output 0 and digital output 1: The 'user-defined pages' are simple HTML files (can also contain JavaScript, CSS, linking to other files, etc.) which contain specific tags (called awp-commands) which correspond to PLC-internal data-blocks. Activating the user-defined pages inside the user program is done by moving the 'WWW' data block from the 'Instructions' side-pane into the current program block (TIA Portal).

The web server can easily be configured in Step 7, by enabling it and adding 'user-defined pages'. In this case I will introduce a client written in Python using the requests library (and Tkinter to display a GUI). The client which requests data from the S7 web-API can be a web app running on the S7 written in JavaScript but can also be any other client. With a bit of fortunes it can easily be achieved to 'configure' the integrated web server to respond with a JSON or XML (or any other text based format) to a http/s request. Therefore, the access to variables and tags inside the PLC is not limited to the S7-1200 native web frontend, it is also possible to develop user-defined pages (or rather web apps) using JavaScript and HTML. The Siemens Simatic S7-1200 PLC comes with an integrated web server which just needs to be activated for the specific project. It is used in web-services and is one possibility to achieve M2M (Machine-to-Machine) communication. ReST (Representational State Transfer) is an often used technique in distributed environments to simplify the data exchange between devices.