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packet_handler.py
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executable file
·460 lines (382 loc) · 13.1 KB
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"""Low-level communication for PSLab.
Example
-------
>>> from PSL.packet_handler import Handler
>>> device = Handler()
>>> version = device.get_version()
>>> device.disconnect()
"""
import logging
import os.path
import platform
import struct
import time
from functools import partial, update_wrapper
from typing import List, Union
import serial
from serial.tools import list_ports
import PSL.commands_proto as CP
logger = logging.getLogger(__name__)
USB_VID = 0x04D8
USB_PID = 0x00DF
class Handler:
"""Provides methods for communicating with the PSLab hardware.
When instantiated, Handler tries to connect to the PSLab. A port can optionally
be specified; otherwise Handler will try to find the correct port automatically.
Parameters
----------
See :meth:`connect. <PSL.packet_handler.Handler.connect>`.
"""
def __init__(
self,
port: str = None,
baudrate: int = 1000000,
timeout: float = 1.0,
**kwargs, # Backward compatibility
):
self._check_udev()
self.burst_buffer = b""
self.load_burst = False
self.input_queue_size = 0
self.version = ""
self._log = b""
self._logging = False
self.interface = serial.Serial()
self.send_byte = partial(self._send, size=1)
update_wrapper(self.send_byte, self._send)
self.send_int = partial(self._send, size=2)
update_wrapper(self.send_int, self._send)
self.get_byte = partial(self._receive, size=1)
update_wrapper(self.get_byte, self._receive)
self.get_int = partial(self._receive, size=2)
update_wrapper(self.get_int, self._receive)
self.get_long = partial(self._receive, size=4)
update_wrapper(self.get_long, self._receive)
self.connect(port=port, baudrate=baudrate, timeout=timeout)
# Backwards compatibility
self.fd = self.interface
self.occupiedPorts = set()
self.connected = self.interface.is_open
self.__sendByte__ = self.send_byte
self.__sendInt__ = self.send_int
self.__get_ack__ = self.get_ack
self.__getByte__ = self.get_byte
self.__getInt__ = self.get_int
self.__getLong__ = self.get_long
self.waitForData = self.wait_for_data
self.sendBurst = self.send_burst
self.portname = self.interface.name
self.listPorts = self._list_ports
@staticmethod
def _check_udev():
if platform.system() == "Linux":
udev_paths = [
"/run/udev/rules.d/",
"/etc/udev/rules.d/",
"/lib/udev/rules.d/",
]
for p in udev_paths:
udev_rules = os.path.join(p, "99-pslab.rules")
if os.path.isfile(udev_rules):
break
else:
e = (
"A udev rule must be installed to access the PSLab. "
+ "Please copy 99-pslab.rules to /etc/udev/rules.d/."
)
raise OSError(e)
@staticmethod
def _list_ports() -> List[str]: # Promote to public?
"""Return a list of serial port names."""
return [p.device for p in list_ports.comports()]
def connect(
self,
port: str = None,
baudrate: int = 1000000,
timeout: float = 1.0,
):
"""Connect to PSLab.
Parameters
----------
port : str, optional
The name of the port to which the PSLab is connected as a string. On
Posix this is a path, e.g. "/dev/ttyACM0". On Windows, it's a numbered
COM port, e.g. "COM5". Will be autodetected if not specified.
baudrate : int, optional
Symbol rate in bit/s. The default value is 1000000.
timeout : float, optional
Time in seconds to wait before cancelling a read or write command. The
default value is 1.0.
Raises
------
SerialException
If connection could not be established.
"""
# serial.Serial opens automatically if port is not None.
self.interface = serial.Serial(
port=port,
baudrate=baudrate,
timeout=timeout,
write_timeout=timeout,
)
if self.interface.is_open:
# User specified a port.
version = self.get_version()
else:
port_info_generator = list_ports.grep(f"{USB_VID:04x}:{USB_PID:04x}")
for port_info in port_info_generator:
self.interface.port = port_info.device
self.interface.open()
version = self.get_version()
if any(expected in version for expected in ["PSLab", "CSpark"]):
break
else:
version = ""
if any(expected in version for expected in ["PSLab", "CSpark"]):
self.version = version
self.fd = self.interface # Backward compatibility
logger.info(f"Connected to {self.version} on {self.interface.port}.")
else:
self.interface.close()
self.version = ""
raise serial.SerialException("Device not found.")
def disconnect(self):
"""Disconnect from PSLab."""
self.interface.close()
def reconnect(
self,
port: str = None,
baudrate: int = None,
timeout: float = None,
):
"""Reconnect to PSLab.
Will reuse previous settings (port, baudrate, timeout) unless new ones are
provided.
Parameters
----------
See :meth:`connect. <PSL.packet_handler.Handler.connect>`.
"""
self.disconnect()
# Reuse previous settings unless user provided new ones.
baudrate = self.interface.baudrate if baudrate is None else baudrate
port = self.interface.port if port is None else port
timeout = self.interface.timeout if timeout is None else timeout
self.interface = serial.Serial(
port=port,
baudrate=baudrate,
timeout=timeout,
write_timeout=timeout,
)
self.connect()
def get_version(self, *args) -> str: # *args for backwards compatibility
"""Query PSLab for its version and return it as a decoded string.
Returns
-------
str
Version string.
"""
self.send_byte(CP.COMMON)
self.send_byte(CP.GET_VERSION)
version = self.interface.readline()
self._write_log(version, "RX")
return version.decode("utf-8")
def get_ack(self) -> int: # Make _internal?
"""Get response code from PSLab.
Also functions as handshake.
Returns
-------
int
Response code. Meanings:
1 SUCCESS
2 ARGUMENT_ERROR
3 FAILED
"""
if not self.load_burst:
response = self.read(1)
else:
self.input_queue_size += 1
return 1
try:
return CP.Byte.unpack(response)[0]
except Exception as e:
logger.error(e)
return 3 # raise exception instead?
@staticmethod
def _get_integer_type(size: int) -> struct.Struct:
if size == 1:
return CP.Byte
elif size == 2:
return CP.ShortInt
elif size == 4:
return CP.Integer
else:
raise ValueError("size must be 1, 2, or 4.")
def _send(self, value: Union[bytes, int], size: int):
"""Send a value to the PSLab.
Parameters
----------
value : int
Value to send to PSLab. Must fit in four bytes.
"""
if isinstance(value, bytes):
packet = value
else:
packer = self._get_integer_type(size)
packet = packer.pack(value)
if self.load_burst:
self.burst_buffer += packet
else:
self.write(packet)
def _receive(self, size: int) -> int:
"""Read and unpack data from the serial port.
Returns
-------
int
Unpacked data, or -1 if too few bytes were read.
"""
received = self.read(size)
if len(received) == size:
unpacker = self._get_integer_type(size)
retval = unpacker.unpack(received)[0]
else:
logger.error(f"Requested {size} bytes, got {len(received)}.")
retval = -1 # raise an exception instead?
return retval
def read(self, number_of_bytes: int) -> bytes:
"""Log incoming bytes.
Wrapper for Serial.read().
Parameters
----------
number_of_bytes : int
Number of bytes to read from the serial port.
Returns
-------
bytes
Bytes read from the serial port.
"""
data = self.interface.read(number_of_bytes)
self._write_log(data, "RX")
return data
def write(self, data: bytes):
"""Log outgoing bytes.
Wrapper for Serial.write().
Parameters
----------
data : int
Bytes to write to the serial port.
"""
self.interface.write(data)
self._write_log(data, "TX")
def _write_log(self, data: bytes, direction: str):
if self._logging:
self._log += direction.encode() + data + "STOP".encode()
def wait_for_data(self, timeout: float = 0.2) -> bool:
"""Wait for :timeout: seconds or until there is data in the input buffer.
Parameters
----------
timeout : float, optional
Time in seconds to wait. The default is 0.2.
Returns
-------
bool
True iff the input buffer is not empty.
"""
start_time = time.time()
while time.time() - start_time < timeout:
if self.interface.in_waiting:
return True
time.sleep(0.02)
return False
def send_burst(self) -> List[int]:
"""Transmit the commands stored in the burst_buffer.
The burst_buffer and input buffer are both emptied.
The following example initiates the capture routine and sets OD1 HIGH
immediately. It is used by the Transient response experiment where the input
needs to be toggled soon after the oscilloscope has been started.
Example
-------
>>> I.load_burst = True
>>> I.capture_traces(4, 800, 2)
>>> I.set_state(I.OD1, I.HIGH)
>>> I.send_burst()
Returns
-------
list
List of response codes
(see :meth:`get_ack <PSL.packet_handler.Handler.get_ack>`).
"""
self.write(self.burst_buffer)
self.burst_buffer = b""
self.load_burst = False
acks = self.read(self.input_queue_size)
self.input_queue_size = 0
return list(acks)
RECORDED_TRAFFIC = iter([])
"""An iterator returning (request, response) pairs.
The request is checked against data written to the dummy serial port, and if it matches
the response can be read back. Both request and response should be bytes-like.
Intended to be monkey-patched by the calling test module.
"""
class MockHandler(Handler):
"""Mock implementation of :class:`Handler` for testing.
Parameters
----------
Same as :class:`Handler`.
"""
VERSION = "PSLab vMOCK"
def __init__(
self,
port: str = None,
baudrate: int = 1000000,
timeout: float = 1.0,
):
self._in_buffer = b""
super().__init__(port, baudrate, timeout)
@staticmethod
def _check_udev():
pass
def connect(
self,
port: str = None,
baudrate: int = 1000000,
timeout: float = 1.0,
):
"""See :meth:`Handler.connect`."""
self.version = self.get_version()
def disconnect(self):
"""See :meth:`Handler.disconnect`."""
pass
def reconnect(
self,
port: str = None,
baudrate: int = None,
timeout: float = None,
):
"""See :meth:`Handler.reconnect`."""
pass
def get_version(self, *args) -> str:
"""Return mock version."""
return self.VERSION
def read(self, number_of_bytes: int) -> bytes:
"""Mimic the behavior of the serial bus by returning recorded RX traffic.
The returned data depends on how :meth:`write` was called prior to calling
:meth:`read`.
See also :meth:`Handler.read`.
"""
read_bytes = self._in_buffer[:number_of_bytes]
self._in_buffer = self._in_buffer[number_of_bytes:]
return read_bytes
def write(self, data: bytes):
"""Add recorded RX data to buffer if written data equals recorded TX data.
See also :meth:`Handler.write`.
"""
tx, rx = next(RECORDED_TRAFFIC)
if tx == data:
self._in_buffer += rx
def wait_for_data(self, timeout: float = 0.2) -> bool:
"""Return True if there is data in buffer, or return False after timeout."""
if self._in_buffer:
return True
else:
time.sleep(timeout)
return False