do the whole RS485 DE handling in Python

src/MyRS485.py

@@ -0,0 +1,26 @@
+import serial
+import serial.serialutil
+import ctypes
+import wiringpi
+import array
+import fcntl
+import termios
+
+DE_PIN = 0
+
+class MyRS485(serial.Serial):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        wiringpi.wiringPiSetup()
+        wiringpi.pinMode(DE_PIN, wiringpi.OUTPUT)
+        self.buf = array.array('h', [0])
+
+    def write(self, b):
+        wiringpi.digitalWrite(DE_PIN, wiringpi.HIGH)
+        super.write(b)
+        while True:
+            fcntl.ioctl(self.fileno(), termios.TIOCSERGETLSR, self.buf, 1)
+            if self.buf[0] & termios.TIOCSER_TEMT:
+                break
+        wiringpi.digitalWrite(DE_PIN, wiringpi.LOW)
+