VISA error handeled in PICA

Author: prathameshnium

docs/User_Manual.md

@@ -83,9 +83,9 @@ This approach, however, leads to a considerable degree of code repetition becaus
 >
 > Choose one of the following:
 > - **NI-VISA:** The industry standard from National Instruments. Download and install it from the [NI website](https://www.ni.com/en/support/downloads/drivers/download.ni-visa.html#575764).
-> - **PyVISA-py:** A backend written in pure Python that is installed automatically with PICA. It can be used as a fallback but may have limitations compared to vendor-specific drivers like NI-VISA.
+> - **PyVISA-py:** A backend written in pure Python. Install it using `pip install pyvisa-py`. It can be used as a fallback but may have limitations compared to vendor-specific drivers like NI-VISA.
 >
-> **Before proceeding, verify your VISA installation.**
+> **Before proceeding, verify your VISA installation.** For more details and troubleshooting, refer to the "[Common Issues & Troubleshooting](#6-common-issues--troubleshooting)" section.
 
 ### 3.2 Getting Started
 

pica/main.py

@@ -32,6 +32,7 @@
 
 try:
     import pyvisa
+    import pyvisa.errors # Import pyvisa.errors
     PYVISA_AVAILABLE = True
 except ImportError:
     PYVISA_AVAILABLE = False
@@ -1058,6 +1059,11 @@ def _gpib_scan_worker(self):
                     except Exception as e:
                         result = f"Address: {address}\n    Error: Could not get ID. {e}\n\n"
                         self.result_queue.put(result)
+        except pyvisa.errors.VisaIOError:
+            error_msg = (
+                "PICA could not find a VISA backend. Please install NI-VISA or run pip install pyvisa-py.\n"
+                "Refer to the 'Troubleshooting Installation' section in the documentation for more details.\n")
+            self.result_queue.put(error_msg)
         except Exception as e:
             error_msg = (
                 f"A critical VISA error occurred: {e}\n"