pypck is an open source library written in Python which allows the connection to the LCN (local control network) system. It uses the vendor protocol LCN-PCK. To get started an unused license of the coupling software LCN-PCHK and a hardware coupler is necessary.
pypck is used by the LCN integration of the Home Assistant project.
"""Example for switching an output port of module 10 on and off."""
import asyncio
from pypck.connection import PchkConnectionManager
from pypck.lcn_addr import LcnAddr
async def main():
"""Connect to PCK host, get module object and switch output port on and off."""
async with PchkConnectionManager(
"192.168.2.41",
4114,
username="lcn",
password="lcn",
settings={"SK_NUM_TRIES": 0},
) as pck_client:
module = pck_client.get_address_conn(LcnAddr(0, 10, False))
await module.dim_output(0, 100, 0)
await asyncio.sleep(1)
await module.dim_output(0, 0, 0)
asyncio.run(main())
pypck relies heavily on asyncio for talking to the LCN-PCHK software. This makes it unusable with the standard python interactive interpreter. Fortunately, ipython provides some support for asyncio in its interactive interpreter, see ipython autoawait.
Python 3.8.3 (default, Jun 9 2020, 17:39:39)
Type 'copyright', 'credits' or 'license' for more information
IPython 7.19.0 -- An enhanced Interactive Python. Type '?' for help.
In [1]: from pypck.connection import PchkConnectionManager
...: from pypck.lcn_addr import LcnAddr
...: import asyncio
In [2]: connection = PchkConnectionManager(host='localhost', port=4114, username='lcn', password='lcn')
In [3]: await connection.async_connect()
In [4]: module = connection.get_address_conn(LcnAddr(seg_id=0, addr_id=10, is_group=False), request_serials=False)
In [5]: await module.request_serials()
Out[5]:
{'hardware_serial': 127977263668,
'manu': 1,
'software_serial': 1771023,
'hardware_type': <HardwareType.UPU: 26>}
In [6]: await module.dim_output(0, 100, 0)
...: await asyncio.sleep(1)
...: await module.dim_output(0, 0, 0)
Out[6]: True
ipython starts and stops the asyncio event loop for each toplevel command sequence. Also it only starts the loop if the toplevel commands includes async code (like await or a call to an async function). This can lead to unexpected behavior. For example, background tasks run only while ipython is executing toplevel commands that started the event loop. Functions that use the event loop only internally may fail, e.g. the following would fail:
In [4]: module = connection.get_address_conn(LcnAddr(seg_id=0, addr_id=10, is_group=False), request_serials=True)
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-7-cd663974bde2> in <module>
----> 1 module = connection.get_address_conn(modaddr)
/pypck/connection.py in get_address_conn(self, addr, request_serials)
457 address_conn = ModuleConnection(self, addr)
458 if request_serials:
--> 459 self.request_serials_task = asyncio.create_task(
460 address_conn.request_serials()
461 )
/usr/local/lib/python3.8/asyncio/tasks.py in create_task(coro, name)
379 Return a Task object.
380 """
--> 381 loop = events.get_running_loop()
382 task = loop.create_task(coro)
383 _set_task_name(task, name)
RuntimeError: no running event loop
See ipython autoawait internals for details.