forked from BrewPi/brewpi-script
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backgroundserial.py
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backgroundserial.py
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from __future__ import print_function
import threading
import Queue
import sys
import time
from BrewPiUtil import printStdErr, logMessage
from serial import SerialException, serial_for_url
from expandLogMessage import filterOutLogMessages
import autoSerial
class BackGroundSerial():
def __init__(self, port):
self.buffer = ''
self.port = port
self.ser = None
self.queue = Queue.Queue()
self.messages = Queue.Queue()
self.thread = None
self.fatal_error = None
self.stop_event = threading.Event()
self.start()
self.error = None
# public interface only has 4 functions: start/stop/read_line/write
def start(self):
self.stop_event.clear()
if not self.thread:
self.thread = threading.Thread(target=self.__listen_thread, kwargs={'stop_event': self.stop_event})
self.thread.setDaemon(True)
self.thread.start()
def stop(self):
self.stop_event.set()
if self.thread is not None:
start = time.time()
while(self.thread.isAlive()):
time.sleep(0.1) # give time to close
if time.time() - start > 5:
self.fatal_error = "Cannot stop Serial background thread"
break
self.thread = None
def connected(self):
return self.ser is not None
def read_line(self):
self.exit_on_fatal_error()
try:
return self.queue.get_nowait()
except Queue.Empty:
return None
def read_message(self):
self.exit_on_fatal_error()
try:
return self.messages.get_nowait()
except Queue.Empty:
return None
def writeln(self, data):
return self.write(data + "\n")
def write(self, data):
self.exit_on_fatal_error()
# Prevent writing to a port in error state.
# This will leave unclosed handles to serial on the system
written = 0
if self.ser:
try:
written = self.ser.write(data)
except (IOError, OSError, SerialException) as e:
logMessage('Serial Error: {0})'.format(str(e)))
return written
def exit_on_fatal_error(self):
if self.fatal_error is not None:
self.stop()
logMessage(self.fatal_error)
sys.exit("Terminating due to fatal serial error")
def __listen_thread(self, stop_event):
logMessage('Background thread for serial started')
while not stop_event.is_set():
if not self.ser:
serial_port = autoSerial.find_port(self.port)
try:
if serial_port is not None:
self.ser = serial_for_url(serial_port['device'], baudrate=57600, timeout=0.1, write_timeout=0.1)
self.ser.inter_byte_timeout = 0.01 # necessary because of bug in in_waiting with sockets
self.ser.flushInput()
self.ser.flushOutput()
if "socket://" in serial_port['device']:
logMessage('Serial (re)connected over WiFi at {0}'.format(
serial_port.get('device') or "unknown location"
)
)
else:
logMessage('Serial (re)connected for {0} [{1}] at port: {2}'.format(
serial_port.get('product') or 'unknown product',
serial_port.get('serial_number') or 'unknown serial number',
serial_port.get('name') or 'unknown location'
)
)
self.writeln('r') # ask device to print reset reason if disconnection was due to reset
except (IOError, OSError, SerialException) as e:
if self.ser:
self.ser.close()
self.ser = None
error = str(e)
if error != self.error:
#only print once
self.error = error
logMessage('Error opening serial: {0}'.format(self.error))
time.sleep(1)
else:
new_data = ""
try:
while self.ser.in_waiting > 0:
# for sockets, in_waiting returns 1 instead of the actual number of bytes
# this is a workaround for that
new_data = new_data + self.ser.read(self.ser.in_waiting)
except (IOError, OSError, SerialException) as e:
logMessage('Serial Error: {0})'.format(str(e)))
self.ser.close()
self.ser = None
if len(new_data) > 0:
self.buffer = self.buffer + new_data
while True:
line_from_buffer = self.__get_line_from_buffer()
if line_from_buffer:
self.queue.put(line_from_buffer)
else:
break
# max 10 ms delay. At baud 57600, max 576 characters are received while waiting
time.sleep(0.01)
logMessage('Background thread for serial stopped')
if self.ser:
self.ser.close()
self.ser = None
def __get_line_from_buffer(self):
while '\n' in self.buffer:
stripped_buffer, messages = filterOutLogMessages(self.buffer)
if len(messages) > 0:
for message in messages:
self.messages.put(message)
self.buffer = stripped_buffer
continue
lines = self.buffer.partition('\n') # returns 3-tuple with line, separator, rest
if not lines[1]:
# '\n' not found, first element is incomplete line
self.buffer = lines[0]
return None
else:
# complete line received, [0] is complete line [1] is separator [2] is the rest
self.buffer = lines[2]
return self.__ascii_to_unicode(lines[0])
# remove extended ascii characters from string, because they can raise UnicodeDecodeError later
def __ascii_to_unicode(self, s):
s = s.replace(chr(0xB0), '°')
return unicode(s, 'ascii', 'ignore')
if __name__ == '__main__':
# some test code that requests data from serial and processes the response json
import simplejson
import BrewPiUtil as util
config_file = util.addSlash(sys.path[0]) + 'settings/config.cfg'
config = util.readCfgWithDefaults(config_file)
bg_ser = BackGroundSerial('auto')
bg_ser.start()
success = 0
fail = 0
for i in range(1, 5):
# request control variables 4 times.
# This would overrun buffer if it was not read in a background thread
# the json decode will then fail, because the message is clipped
bg_ser.writeln('v')
bg_ser.writeln('v')
bg_ser.writeln('v')
bg_ser.writeln('v')
bg_ser.writeln('v')
line = True
while line:
line = bg_ser.read_line()
if line:
if line[0] == 'V':
try:
decoded = simplejson.loads(line[2:])
print("Success")
success += 1
except simplejson.JSONDecodeError:
logMessage("Error: invalid JSON parameter string received: " + line)
fail += 1
else:
print(line)
time.sleep(5)
print("Successes: {0}, Fails: {1}".format(success, fail))