[ale] Anyone familiar with Python?

[Alex Carver]

On 2016-03-08 13:24, Pete Hardie wrote:
> My first thought is not so much Python-related as design related.  If you
> want to have only one instance of the wire, you need to make it so that the
> base class functions are either bound to the class, or to an object passed
> in, so you can use the same 'wire' object for each sensor class
> 
> (I am assuming that you are dealing with just a single one of these buses)

Yep, only one address.  But passing it in made sense.  I split off the
serial into a top level class within the imported module and then turned
it into a parameter for the other classes.

I had hoped for a slightly more "automagic" method where the serial port
was already in place without having to pass it as an argument but that
doesn't appear to be possible.  Fortunately I only have to pass it once
when the class is instantiated.

> 
> 
> On Tue, Mar 8, 2016 at 4:12 PM, Alex Carver <agcarver+ale at acarver.net>
> wrote:
> 
>> Ok, so this should be fun since I've spent the past hour and a half on
>> Google and haven't really gotten anywhere.
>>
>> I'm writing some code to control data collection modules.  Physically,
>> all the modules are hanging off an RS485 bus with a single wire to the
>> computer.  Each of the modules has a set of very core commands
>> (specifically for things like fetching the module name, firmware number,
>> and base configuration) and then it has module specific commands that
>> vary depending on the type of module (read voltage inputs, set relays on
>> outputs, etc.)  All of the modules share the same protocol for comms.
>>
>> So my original thought was to create a class which contained the very
>> bottom stuff, serial I/O/ that would handle the basic serial functions
>> and the protocol.  Let's call this data_collectors.
>>
>> I then thought to make a subclass of data_collectors that contains the
>> more specific functions mapped to the protocol commands (e.g. I'd have a
>> get_voltage() function for the specific voltage input module and a
>> set_relay() function for a relay output module).  The modules each have
>> their own address.
>>
>> So in code form (some pseudo code in here, too for brevity):
>>
>> <file is my_data_collector_file>
>> class data_collector(object):
>>
>>         serial_port = None
>>
>>         def open_port(self, tty=''):
>>                 self.serial_port = serial.open(tty)
>>
>>         def write_port(...):
>>
>>         def read_port(...):
>>
>>         def get_module_name(...):
>>                 write_port()
>>                 read_port()
>>
>> class voltage_input(data_collector):
>>         __init__(self, module_address):
>>                 self.module_address  = module_address
>>
>>         get_voltage(self, channel):
>>                 <stuff here including write_port() read_port()>
>>
>> class relay_output(data_collector):
>>         __init__(self, module_address):
>>                 self.module_address = module_address
>>
>>
>>         set_relay(self, channel, value):
>>                 <stuff here including value validation, write_port(),
>> read_port()
>>
>>
>> The goal was to be able to import this block of code and then do the
>> following (somehow):
>>
>> import my_data_collector_file as my_dcf
>>
>> dcf.open_port(tty=...0)  #somehow do this, not sure how
>> gauges = dcf.voltage_input(module_address=1)
>> valves = dcf.relay_output(module_address=2)
>>
>>
>> Right now, with the same structure I can execute the gauges = and valves
>> = lines but they get independent copies of the base class.  I want to
>> share the base class (so the port opens and stays open) among all of the
>> subclasses but have the subclasses behave individually (since they each
>> have their own set of commands that don't overlap).
>>
>> I haven't figured out if there's a way to accomplish this even if
>> there's a third call (as above with the dcf.open_port) to just get
>> everything started.
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> 
> 
> 
> 
> 
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