Getters and Setters Configuration

To use the Command Reader GettersAndSetters, you must define "getters_and_setters" as a dictionary in your configuration.

Dictionary Sections

The different sections inside this dictionary are

“default_values”

The default values for the attributes that you will be storing, that is, the values they will be initially set to if you call a getter before you call a setter.

“getters”

The getter serial commands and their responses. The getter commands are specified as a string with your eol characters, and the response is a string with Jinja2 variable formatting.

This allows you to do basic equations inside the response, such as combining multiple attributes, doing unit conversion, and other things.

“setters”

The setter serial commands and their responses. The setter commands change the stored attributes you initially set up inside "default_values". Both the commands and responses uses Jinja2 variable formatting.

Caution

The jinja2 formatting inside the cmd field for setters currently can only accept the name of an attribute

Example

>>> from granola import Cereal

>>> command_readers = {
...     "GettersAndSetters": {
...         "default_values": {"sn": "42", "temp": "20.0", "conversion_factor": "7.0"},
...         "getters": [
...             {"cmd": "get -sn\r", "response": "{{ sn }}\r>"},
...             {"cmd": "get -temp\r", "response": "{{ temp }}\r>"},
...             {"cmd": "get -tempf\r", "response": "{{ temp|float * (9/5) + 32 }}\r>"},
...             {"cmd": "get temp_convt\r", "response": "{{ (temp|float + conversion_factor|float) / 2 }}"},
...         ],
...         "setters": [
...             {"cmd": "set -sn {{sn}}\r", "response": "OK\r>"},
...             {"cmd": "set sn and temp {{ sn }} {{ temp }}\r", "response": "serial number {{ sn }} temp: {{temp}}"},
...             {"cmd": "set -temp {{ temp }}\r", "response": "{{ temp }}"},
...             {"cmd": "set convt {{ conversion_factor }}\r", "response": "Conversion Factor {{ conversion_factor }}"},
...         ],
...     }
... }
>>> cereal = Cereal(command_readers=command_readers)
>>> cereal.write(b"get -sn\r")
8
>>> cereal.read(cereal.in_waiting)
b'42\r>'
>>> cereal.write(b"set -sn granola42\r")
18
>>> cereal.read(cereal.in_waiting)
b'OK\r>'
>>> cereal.write(b"get -sn\r")
8
>>> cereal.read(cereal.in_waiting)
b'granola42\r>'
>>> cereal.write(b"get -tempf\r")
11
>>> cereal.read(cereal.in_waiting)
b'68.0\r>'

Customizing Jinja

If the default jinja2 templating characters are incompatible with your serial commands, you can configure those in your configuration dictionary as so.

>>> command_readeres = {
...     "GettersAndSetters": {
...         "default_values": {"sn": "42"},
...         "getters": [{"cmd": "get -sn\r", "response": "`sn`\r>"}],
...         "setters": [{"cmd": "set -sn `sn`\r", "response": "OK\r>"}],
...         "variable_start_string": "`",
...         "variable_end_string": "`",
...     }
... }
>>>
>>> cereal = Cereal(command_readers=command_readers)
>>> cereal.write(b"set -sn granola42\r")
18
>>> cereal.read(cereal.in_waiting)
b'OK\r>'
>>> cereal.write(b"get -sn\r")
8
>>> cereal.read(cereal.in_waiting)
b'granola42\r>'