156 lines
4.2 KiB
Python
156 lines
4.2 KiB
Python
import json
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import serial
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import threading
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import time
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from platypush.plugins import Plugin, action
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from platypush.plugins.gpio.sensor import GpioSensorPlugin
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class SerialPlugin(GpioSensorPlugin):
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"""
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The serial plugin can read data from a serial device, as long as the serial
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device returns a JSON. You can use this plugin to interact for example with
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some sensors connected through an Arduino. Just make sure that the code on
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your serial device returns JSON values. If you're using an Arduino or any
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ATMega compatible device, take a look at
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https://github.com/bblanchon/ArduinoJson.
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"""
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def __init__(self, device, baud_rate=9600, *args, **kwargs):
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"""
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:param device: Device path (e.g. ``/dev/ttyUSB0`` or ``/dev/ttyACM0``)
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:type device: str
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:param baud_rate: Serial baud rate (default: 9600)
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:type baud_rate: int
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"""
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super().__init__(*args, **kwargs)
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self.device = device
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self.baud_rate = baud_rate
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self.serial = None
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self.serial_lock = threading.Lock()
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self.last_measurement = None
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def _read_json(self, serial_port):
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n_brackets = 0
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is_escaped_ch = False
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parse_start = False
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output = bytes()
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while True:
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ch = serial_port.read()
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if not ch:
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break
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if ch.decode() == '{' and not is_escaped_ch:
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parse_start = True
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n_brackets += 1
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if not parse_start:
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continue
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output += ch
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if ch.decode() == '}' and not is_escaped_ch:
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n_brackets -= 1
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if n_brackets == 0:
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break
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is_escaped_ch = ch.decode() == '\\'
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return output.decode().strip()
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def _get_serial(self, reset=False):
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if self.serial:
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if not reset:
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return self.serial
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self._close_serial()
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self.serial = serial.Serial(self.device, self.baud_rate)
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return self.serial
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def _close_serial(self):
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if self.serial:
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try:
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self.serial.close()
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self.serial = None
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except Exception as e:
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self.logger.warning('Error while closing serial communication: {}')
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self.logger.exception(e)
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@action
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def get_measurement(self):
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"""
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Reads JSON data from the serial device and returns it as a message
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"""
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data = None
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try:
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serial_available = self.serial_lock.acquire(timeout=2)
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if serial_available:
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try:
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ser = self._get_serial()
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except:
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time.sleep(1)
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ser = self._get_serial(reset=True)
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data = self._read_json(ser)
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try:
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data = json.loads(data)
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except:
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self.logger.warning('Invalid JSON message from {}: {}'.
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format(self.device, data))
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else:
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data = self.last_measurement
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finally:
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try:
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self.serial_lock.release()
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except:
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pass
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if data:
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self.last_measurement = data
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return data
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@action
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def write(self, data):
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"""
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Writes data to the serial device.
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:param data: Data to send to the serial device
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:type data: str, bytes or dict. If dict, it will be serialized as JSON.
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"""
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if isinstance(data, dict):
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data = json.dumps(data)
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if isinstance(data, str):
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data = data.encode('utf-8')
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try:
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serial_available = self.serial_lock.acquire(timeout=2)
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if serial_available:
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try:
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ser = self._get_serial()
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except:
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time.sleep(1)
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ser = self._get_serial(reset=True)
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self.logger.info('Writing {} to {}'.format(data, self.device))
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ser.write(data)
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finally:
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try:
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self.serial_lock.release()
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except:
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pass
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# vim:sw=4:ts=4:et:
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