revamp the serial connection to avoid Tbeam reboots

.pylintrc

@@ -23,7 +23,7 @@ ignore-patterns=mqtt_pb2.py,channel_pb2.py,environmental_measurement_pb2.py,admi
 # no Warning level messages displayed, use"--disable=all --enable=classes
 # --disable=W"
 #
-disable=invalid-name,fixme,logging-fstring-interpolation,too-many-statements,too-many-branches,too-many-locals,no-member,f-string-without-interpolation,protected-access,no-self-use,pointless-string-statement,too-few-public-methods,consider-using-f-string,broad-except,no-else-return,unused-argument,global-statement,global-variable-not-assigned,too-many-boolean-expressions,no-else-raise,bare-except
+disable=invalid-name,fixme,logging-fstring-interpolation,too-many-statements,too-many-branches,too-many-locals,no-member,f-string-without-interpolation,protected-access,no-self-use,pointless-string-statement,too-few-public-methods,consider-using-f-string,broad-except,no-else-return,unused-argument,global-statement,global-variable-not-assigned,too-many-boolean-expressions,no-else-raise,bare-except,c-extension-no-member
 
 
 [BASIC]

meshtastic/serial_interface.py

@@ -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)

meshtastic/stream_interface.py

@@ -62,7 +62,8 @@ class StreamInterface(MeshInterface):
         # because we want to ensure it is looking for START1)
         p = bytearray([START2] * 32)
         self._writeBytes(p)
-        time.sleep(0.1)  # wait 100ms to give device time to start running
+        if not self.noProto:
+            time.sleep(0.1)  # wait 100ms to give device time to start running
 
         self._rxThread.start()
 
@@ -88,6 +89,9 @@ class StreamInterface(MeshInterface):
         if self.stream:  # ignore writes when stream is closed
             self.stream.write(b)
             self.stream.flush()
+            # we sleep here to give the TBeam a chance to work
+            if not self.noProto:
+                time.sleep(0.1)
 
     def _readBytes(self, length):
         """Read an array of bytes from our stream"""