From 8394333cab3ad4f0627a7d4931ba833815b8d3d7 Mon Sep 17 00:00:00 2001
From: Johny Mattsson <jmattsson@dius.com.au>
Date: Thu, 2 Jul 2015 20:09:32 +1000
Subject: [PATCH] Pull in upstream fixes for getting board into flash mode.

---
 tools/esptool.py | 56 +++++++++++++++++++++---------------------------
 1 file changed, 25 insertions(+), 31 deletions(-)

diff --git a/tools/esptool.py b/tools/esptool.py
index 53e10041..17311fb5 100755
--- a/tools/esptool.py
+++ b/tools/esptool.py
@@ -128,38 +128,32 @@ class ESPROM:
     def connect(self):
         print 'Connecting...'
 
-        # RTS = CH_PD (i.e reset)
-        # DTR = GPIO0
-        # self._port.setRTS(True)
-        # self._port.setDTR(True)
-        # self._port.setRTS(False)
-        # time.sleep(0.1)
-        # self._port.setDTR(False)
+        for _ in xrange(4):
+            # issue reset-to-bootloader:
+            # RTS = either CH_PD or nRESET (both active low = chip in reset)
+            # DTR = GPIO0 (active low = boot to flasher)
+            self._port.setDTR(False)
+            self._port.setRTS(True)
+            time.sleep(0.05)
+            self._port.setDTR(True)
+            self._port.setRTS(False)
+            time.sleep(0.05)
+            self._port.setDTR(False)
 
-        # NodeMCU devkit
-        self._port.setRTS(True)
-        self._port.setDTR(True)
-        time.sleep(0.1)
-        self._port.setRTS(False)
-        self._port.setDTR(False)
-        time.sleep(0.1)
-        self._port.setRTS(True)
-        time.sleep(0.1)
-        self._port.setDTR(True)
-        self._port.setRTS(False)
-        time.sleep(0.3)
-        self._port.setDTR(True)
-
-        self._port.timeout = 0.5
-        for i in xrange(10):
-            try:
-                self._port.flushInput()
-                self._port.flushOutput()
-                self.sync()
-                self._port.timeout = 5
-                return
-            except:
-                time.sleep(0.1)
+            self._port.timeout = 0.3 # worst-case latency timer should be 255ms (probably <20ms)
+            for _ in xrange(4):
+                try:
+                    self._port.flushInput()
+                    self._port.flushOutput()
+                    self.sync()
+                    self._port.timeout = 5
+                    return
+                except:
+                    time.sleep(0.05)
+            # this is a workaround for the CH340 serial driver on current versions of Linux,
+            # which seems to sometimes set the serial port up with wrong parameters
+            self._port.close()
+            self._port.open()
         raise Exception('Failed to connect')
 
     """ Read memory address in target """