we can readback preloader version

src/readback/readback

@@ -0,0 +1,56 @@
+#!/usr/bin/env python
+
+import sys
+import serial
+import os.path
+import time
+from struct import pack, unpack
+from socket import ntohs
+
+class MTKSerial(serial.Serial):
+
+    def echo(self, command):
+        self.flushInput()
+        self.write(command)
+        self.flush()
+        return port.read(len(command))
+
+if __name__ == '__main__':
+
+    print 'waiting device connected'
+    while not os.path.exists('/dev/ttyACM0'):
+        time.sleep(1)
+        print '.',
+    print
+
+    port = None
+    connected = False
+    while not connected:
+        print 'opening port'
+        try:
+            port = MTKSerial('/dev/ttyACM0', 921600, timeout = 1 )
+            connected = True
+        except serial.serialutil.SerialException:
+            print 'port is busy'
+
+    print 'reading startup sequence'
+    echo = port.read(10)
+    if 'READY' not in echo:
+        raise Exception('device not ready')
+
+    print 'device ready, trying to be master'
+
+    mastered = False
+    while not mastered:
+        mastered = port.echo("\xA0") == "\x5F"
+
+    print 'device agreed to be slave, completing sequence'
+    assert port.echo("\x0A") == "\xF5"
+    assert port.echo("\x50") == "\xAF"
+    assert port.echo("\x05") == "\xFA"
+
+    print 'device communication channel is ok, asking preloader version'
+    assert port.echo("\xFD") == "\xFD"
+    version, status = unpack('hh', port.read(4))
+    print 'status:', ntohs(status)
+    print 'preloader version reported:', hex(ntohs(version))