Fixed LS240 connection drop crashing acq process

[davidvng]

Changed agent code to handle connection drops without crashing the acq process.

Description

When a connection drop occurs, the process will stop the current loop and attempt to run init_lakeshore to re-initialize the data fields. The re-initialization will try once every second until reconnection and then the loop continues.

Motivation and Context

Addresses connection drop issues seen across all groups using LS240's.
Possibly fixes #418 and any other old issues?

How Has This Been Tested?

Tested by pulling USB connection and re-connecting. Testing environment is a nuc machine at Yale running Ubuntu 18.04 (required for Anyplace coolgear drivers to work). Works on LS240's connected either directly to nuc or to the Anyplace device.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[BrianJKoopman]

This looks good, and is definitely an improvement over having no error handling. I made one small change to handle the slightly less broad Exception instead of BaseException, but other than that I'm happy with this for now.

Sorry this sat forever -- it's not how I initially envisioned handling this, and I might change how it works again soon (generically for all serial devices), but I wanted to get this merged, finally.