Fixes by sinihappo

[sinihappo]

Please test and consider my changes. I modified the code to consistently send '\n' after each command and with this the sleep is avoided and the power supply responds immediately. Now the code also reads until it gets a full line as all responses are single line and terminated with '\n'.

[Lukse]

Thank you for the changes! Looks like something is wrong with the measure function after the changes:

example.py
{'manufacturer': 'Siglent Technologies', 'model': 'SPD3303X', 'sn': 'SPD3XHBXxxxxxx', 'firmware_ver': '1.01.01.02.05', 'hadrware_ver': 'V3.0'}
{'ch1_mode': <MODE.CV: 1>, 'ch2_mode': <MODE.CV: 1>, 'mode': <TRACK.INDEPENDENT: 0>, 'ch1': <STATE.OFF: 0>, 'ch2': <STATE.OFF: 0>}
Traceback (most recent call last):
  File "Z:\5. Development\projects_github\siglent_test\example.py", line 29, in <module>
    r = s.measure(ch = siglent.CHANNEL.CH1, parameter = siglent.PARAMETER.VOLTAGE)
  File "Z:\5. Development\projects_github\siglent_test\siglent_psu_api.py", line 82, in measure
    reply = float(reply)
ValueError: could not convert string to float: ''