Serial collisions cause LS240 to respond with garbage and crashes the agent

[BrianJKoopman]

If multiple programs try to communicate with the 240, junk might be sent back when the agent is querying the sensors. This junk then can't be cast to float here:

socs/socs/Lakeshore/Lakeshore240.py

Line 337 in 9ab5c5e

return float(response)

This causes the acq process to crash. We should catch these instances and log the error, but just move onto the next iteration of the loop and continue querying.

Here are some examples:

2023-02-22T23:53:34+0000 startup-op: launching init_lakeshore
2023-02-22T23:53:34+0000 start called for init_lakeshore
2023-02-22T23:53:34+0000 init_lakeshore:0 Status is now "starting".
2023-02-22T23:53:34+0000 init_lakeshore:0 Status is now "starting".
2023-02-22T23:53:34+0000 attempt 0
2023-02-22T23:53:34+0000 Initialized Lakeshore module: Lake Shore Model 240-2P          (LSA21OT)
2023-02-22T23:53:34+0000 start called for acq
2023-02-22T23:53:34+0000 init_lakeshore:0 Lakeshore initialized with ID: LSA21OT
2023-02-22T23:53:34+0000 acq:1 Status is now "starting".
2023-02-22T23:53:34+0000 init_lakeshore:0 Lakeshore module initialized.
2023-02-22T23:53:34+0000 init_lakeshore:0 Status is now "done".
2023-02-22T23:53:34+0000 acq:1 Status is now "running".
2023-02-23T05:34:52+0000 acq:1 CRASH: [Failure instance: Traceback: <class 'ValueError'>: could not convert string to float: '0292.4\r+00.5789'
/usr/lib/python3.8/threading.py:932:_bootstrap_inner
/usr/lib/python3.8/threading.py:870:run
/usr/local/lib/python3.8/dist-packages/twisted/_threads/_threadworker.py:47:work
/usr/local/lib/python3.8/dist-packages/twisted/_threads/_team.py:182:doWork
--- <exception caught here> ---
/usr/local/lib/python3.8/dist-packages/twisted/python/threadpool.py:244:inContext
/usr/local/lib/python3.8/dist-packages/twisted/python/threadpool.py:260:<lambda>
/usr/local/lib/python3.8/dist-packages/twisted/python/context.py:117:callWithContext
/usr/local/lib/python3.8/dist-packages/twisted/python/context.py:82:callWithContext
/usr/local/lib/python3.8/dist-packages/socs/agents/lakeshore240/agent.py:221:acq
/usr/local/lib/python3.8/dist-packages/socs/Lakeshore/Lakeshore240.py:337:get_reading
]

2023-02-22T23:00:16+0000 startup-op: launching init_lakeshore
2023-02-22T23:00:16+0000 start called for init_lakeshore
2023-02-22T23:00:16+0000 init_lakeshore:0 Status is now "starting".
2023-02-22T23:00:16+0000 init_lakeshore:0 Status is now "starting".
2023-02-22T23:00:16+0000 attempt 0
2023-02-22T23:00:16+0000 Initialized Lakeshore module: Lake Shore Model 240-2P          (LSA21OT)
2023-02-22T23:00:16+0000 start called for acq
2023-02-22T23:00:16+0000 init_lakeshore:0 Lakeshore initialized with ID: LSA21OT
2023-02-22T23:00:16+0000 acq:1 Status is now "starting".
2023-02-22T23:00:16+0000 init_lakeshore:0 Lakeshore module initialized.
2023-02-22T23:00:16+0000 init_lakeshore:0 Status is now "done".
2023-02-22T23:00:16+0000 acq:1 Status is now "running".
2023-02-22T23:06:57+0000 acq:1 CRASH: [Failure instance: Traceback: <class 'ValueError'>: could not convert string to float: 'D-670S-.L,6SN  235000,\r+0.00000'
/usr/lib/python3.8/threading.py:932:_bootstrap_inner
/usr/lib/python3.8/threading.py:870:run
/usr/local/lib/python3.8/dist-packages/twisted/_threads/_threadworker.py:47:work
/usr/local/lib/python3.8/dist-packages/twisted/_threads/_team.py:182:doWork
--- <exception caught here> ---
/usr/local/lib/python3.8/dist-packages/twisted/python/threadpool.py:244:inContext
/usr/local/lib/python3.8/dist-packages/twisted/python/threadpool.py:260:<lambda>
/usr/local/lib/python3.8/dist-packages/twisted/python/context.py:117:callWithContext
/usr/local/lib/python3.8/dist-packages/twisted/python/context.py:82:callWithContext
/usr/local/lib/python3.8/dist-packages/socs/agents/lakeshore240/agent.py:221:acq
/usr/local/lib/python3.8/dist-packages/socs/Lakeshore/Lakeshore240.py:337:get_reading
]
2023-02-22T23:06:57+0000 acq:1 Status is now "done".
2023-02-22T23:53:13+0000 Received SIGTERM, shutting down.

[davidvng]

This error looks exactly like a connection error I'm getting while testing connection drops (unplugging the USB). In my fix, I am able to address this by moving onto the next iteration without the process crashing. For documentation purposes, I label this error as a connection error, but I can add something like: "This might also be multiple programs trying to communicate with the device."

[BrianJKoopman]

Interesting. I do like that additional log message you suggest.

I'm catching up on emails/PRs, and hope to get to #430 soon.