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revamp the serial connection to avoid Tbeam reboots

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This commit is contained in:
Mike Kinney
2021-12-29 19:24:26 -08:00
parent 047f43534f
commit c70d36d2cd
3 changed files with 32 additions and 42 deletions
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66
meshtastic/serial_interface.py
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@@ -1,9 +1,8 @@
""" Serial interface class
"""
import logging
import platform
import os
import stat
import time
import termios
import serial
import meshtastic.util
@@ -20,6 +19,7 @@ class SerialInterface(StreamInterface):
devPath {string} -- A filepath to a device, i.e. /dev/ttyUSB0 (default: {None})
debugOut {stream} -- If a stream is provided, any debug serial output from the device will be emitted to that stream. (default: {None})
"""
self.noProto = noProto
if devPath is None:
ports = meshtastic.util.findPorts()
@@ -35,43 +35,29 @@ class SerialInterface(StreamInterface):
logging.debug(f"Connecting to {devPath}")
# Note: we provide None for port here, because we will be opening it later
self.stream = serial.Serial(
None, 921600, exclusive=True, timeout=0.5, write_timeout=0)
# first we need to set the HUPCL so the device will not reboot based on RTS and/or DTR
# see https://github.com/pyserial/pyserial/issues/124
if not self.noProto:
with open(devPath, encoding='utf8') as f:
attrs = termios.tcgetattr(f)
attrs[2] = attrs[2] & ~termios.HUPCL
termios.tcsetattr(f, termios.TCSAFLUSH, attrs)
f.close()
time.sleep(0.1)
# rts=False Needed to prevent TBEAMs resetting on OSX, because rts is connected to reset
self.stream.port = devPath
self.stream = serial.Serial(devPath, 921600, exclusive=True, timeout=0.5)
if not self.noProto:
self.stream.flush()
time.sleep(0.1)
# HACK: If the platform driving the serial port is unable to leave the RTS pin in high-impedance
# mode, set RTS to false so that the device platform won't be reset spuriously.
# Linux does this properly, so don't apply this hack on Linux (because it makes the reset button not work).
if self._hostPlatformAlwaysDrivesUartRts():
self.stream.rts = False
self.stream.open()
StreamInterface.__init__(self, debugOut=debugOut, noProto=noProto, connectNow=connectNow)
StreamInterface.__init__(
self, debugOut=debugOut, noProto=noProto, connectNow=connectNow)
"""true if platform driving the serial port is Windows Subsystem for Linux 1."""
def _isWsl1(self):
# WSL1 identifies itself as Linux, but has a special char device at /dev/lxss for use with session control,
# e.g. /init. We should treat WSL1 as Windows for the RTS-driving hack because the underlying platfrom
# serial driver for the CP21xx still exhibits the buggy behavior.
# WSL2 is not covered here, as it does not (as of 2021-May-25) support the appropriate functionality to
# share or pass-through serial ports.
try:
# Claims to be Linux, but has /dev/lxss; must be WSL 1
return platform.system() == 'Linux' and stat.S_ISCHR(os.stat('/dev/lxss').st_mode)
except:
# Couldn't stat /dev/lxss special device; not WSL1
return False
def _hostPlatformAlwaysDrivesUartRts(self):
# OS-X/Windows seems to have a bug in its CP21xx serial drivers. It ignores that we asked for no RTSCTS
# control and will always drive RTS either high or low (rather than letting the CP102 leave
# it as an open-collector floating pin).
# TODO: When WSL2 supports USB passthrough, this will get messier. If/when WSL2 gets virtual serial
# ports that "share" the Windows serial port (and thus the Windows drivers), this code will need to be
# updated to reflect that as well -- or if T-Beams get made with an alternate USB to UART bridge that has
# a less buggy driver.
return platform.system() != 'Linux' or self._isWsl1()
def close(self):
"""Close a connection to the device"""
if not self.noProto:
self.stream.flush()
time.sleep(0.1)
self.stream.flush()
time.sleep(0.1)
logging.debug("Closing Serial stream")
StreamInterface.close(self)