works, but license issues due to bcm2835 lib

pyserialext/RS485Ext.py

@@ -0,0 +1,19 @@
+import serial.rs485
+import serial.serialutil
+import ctypes
+
+
+class RS485Ext(serial.rs485.RS485):
+    def __init__(self, *args, **kwargs):
+        super(RS485Ext, self).__init__(*args, **kwargs)
+        self.writec = ctypes.cdll.LoadLibrary('writec.so')
+        fd = self.fileno()
+        r = self.writec.set_rs485_mode(fd)
+
+    def write(self, b):
+        d = serial.serialutil.to_bytes(b)
+        l = len(d)
+        fd = self.fileno()
+        r = self.writec.writec(fd, d, l)
+        return r
+