fix: reduce high CPU usage in serial monitor

[CFM880]

Description:

Problem

The current implementation uses ser.in_waiting inside a tight loop:

while not stop_event.is_set():
    if ser.in_waiting:
        ...

cfm880@cfm880:~$ py-spy top --pid 34326


Collecting samples from 'python /home/cfm880/sources/git_clone/TuyaOpen/tools/tyCollecting samples from 'python /home/cfm880/sources/git_clone/TuyaOpen/tools/tyCollecting samples from 'python 
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/home/cfm880/sources/git_clone/TuyaOpen/tools/tyCollecting samples from 'python /home/cfm880/sources/git_clone/TuyaOpen/tools/tyutool/tyutool_cli.py monitor -d T5AI' (python v3.13.5)
Total Samples 5592
GIL: 48.00%, Active: 102.00%, Threads: 3

  %Own   %Total  OwnTime  TotalTime  Function (filename)                        
100.00% 100.00%   55.29s    55.29s   in_waiting (serial/serialposix.py)
  1.00%   1.00%    1.21s     1.21s   join (threading.py)
  1.00%   1.00%    1.20s     1.20s   send_data (tyutool/cli/cli_monitor.py)
  0.00% 100.00%   0.520s    55.91s   receive_data (tyutool/cli/cli_monitor.py)
  0.00%   0.00%   0.100s    0.100s   is_set (threading.py)
  0.00% 101.00%   0.000s    57.11s   _bootstrap_inner (threading.py)
  0.00% 101.00%   0.000s    57.11s   _bootstrap (threading.py)
  0.00% 101.00%   0.000s    57.11s   run (threading.py)
  0.00%   1.00%   0.000s     1.21s   <module> (tyutool_cli.py)
  0.00%   1.00%   0.000s     1.21s   __call__ (click/core.py)
  0.00%   1.00%   0.000s     1.21s   cli (tyutool/cli/cli_monitor.py)
  0.00%   1.00%   0.000s     1.21s   cli (tyutool/cli/__init__.py)
  0.00%   1.00%   0.000s     1.21s   main (click/core.py)
  0.00%   1.00%   0.000s     1.21s   invoke (click/core.py)



Press Control-C to quit, or ? for help.

Solution

• Remove ser.in_waiting polling
• Use blocking ser.readline() instead
• Reduce unnecessary flush() calls

Benefits

• CPU usage reduced from ~100% to <1%
• More efficient and power-friendly
• Cleaner and more idiomatic pyserial usage

Testing

• Verified serial communication works as expected
• Ctrl+C exits correctly
• Log file writing is preserved
• cpu result

// after

cfm880@cfm880:~$ py-spy top --pid 50451


Collecting samples from 'python /home/cfm880/sources/git_clone/TuyaOpen/tools/tyCollecting samples from 'python /home/cfm880/sources/git_clone/TuyaOpen/tools/tyCollecting samples from 'python 
.
.
.
/home/cfm880/sources/git_clone/TuyaOpen/tools/tyCollecting samples from 'python /home/cfm880/sources/git_clone/TuyaOpen/tools/tyutool/tyutool_cli.py monitor -d T5AI' (python v3.13.5)
Total Samples 1227
GIL: 0.00%, Active: 15.00%, Threads: 3

  %Own   %Total  OwnTime  TotalTime  Function (filename)                        
  7.00%   7.00%   0.570s    0.570s   join (threading.py)
  8.00%   8.00%   0.410s    0.410s   send_data (tyutool/cli/cli_monitor.py)
  0.00%   0.00%   0.360s    0.360s   read (serial/serialposix.py)
  0.00%   7.00%   0.000s    0.570s   __call__ (click/core.py)
  0.00%   8.00%   0.000s    0.770s   _bootstrap (threading.py)
  0.00%   8.00%   0.000s    0.770s   _bootstrap_inner (threading.py)
  0.00%   7.00%   0.000s    0.570s   main (click/core.py)
  0.00%   7.00%   0.000s    0.570s   <module> (tyutool_cli.py)
  0.00%   7.00%   0.000s    0.570s   cli (tyutool/cli/cli_monitor.py)
  0.00%   0.00%   0.000s    0.360s   receive_data (tyutool/cli/cli_monitor.py)
  0.00%   7.00%   0.000s    0.570s   invoke (click/core.py)
  0.00%   8.00%   0.000s    0.770s   run (threading.py)
  0.00%   7.00%   0.000s    0.570s   cli (tyutool/cli/__init__.py)

Notes

timeout=1 ensures the thread remains responsive to stop_event