# -*- coding: utf-8 -*-
# (c) Copyright 2019 Sensirion AG, Switzerland
from __future__ import absolute_import, division, print_function
from .errors import ShdlcResponseError
import logging
log = logging.getLogger(__name__)
[docs]class ShdlcCommand(object):
"""
Base class for all SHDLC commands.
"""
[docs] def __init__(self, id, data, max_response_time,
min_response_length=0, max_response_length=255,
post_processing_time=0.0):
"""
Constructor.
:param byte id: Command ID (0..255).
:param bytes-like/list data: MOSI data (0..255 bytes).
:param float max_response_time: Maximum time the device needs to
response (used as timeout).
:param byte min_response_length: Minimum expected response length.
:param byte max_response_length: Maximum expected response length.
:param float post_processing_time: Maximum time in seconds the device
needs for post processing
(typically 0.0s).
"""
super(ShdlcCommand, self).__init__()
self._id = id
self._data = bytes(bytearray(data)) # Allow arbitrary iterables
self._max_response_time = max_response_time
self._min_rx_len = min_response_length
self._max_rx_len = max_response_length
self._post_processing_time = post_processing_time
@property
def id(self):
"""
Get the command ID.
:return: Command ID (0..255).
:rtype: byte
"""
return self._id
@property
def data(self):
"""
Get the command data (payload).
:return: Command data (length 0..255).
:rtype: bytes
"""
return self._data
@property
def max_response_time(self):
"""
Get the maximum response time for this command.
:return: Maximum response time in seconds.
:rtype: float
"""
return self._max_response_time
@property
def post_processing_time(self):
"""
Get the post processing time for this command. The post processing time
defines how long a device needs to execute a command *after* responding
to the SHDLC command. Most devices don't need post processing (command
is executed *before* the response is sent). Only special commands (e.g.
a device reset) are executed after the response is sent.
:return: Maximum response time in seconds.
:rtype: float
"""
return self._post_processing_time
[docs] def check_response_length(self, data):
"""
Check if the response length is correct.
:param bytes data: Raw data (payload) received from the device.
:raise ~sensirion_shdlc_driver.errors.ShdlcResponseError:
If length is wrong.
"""
if not (self._min_rx_len <= len(data) <= self._max_rx_len):
raise ShdlcResponseError(
"Wrong response length (expected {}..{} bytes, got {})."
.format(self._min_rx_len, self._max_rx_len, len(data)), data)
[docs] def interpret_response(self, data):
"""
Interpret the response to this command received from the device. This
converts the raw byte array to the actual data type(s) depending on the
sent command.
:param bytes data: Raw data (payload) received from the device.
:return: Interpreted response. Data type and meaning depends on the
sent command. None for commands without response data. See the
actual command implementation for details.
"""
return data if len(data) > 0 else None