Add USB<->serial loopback example to WaveShare Open103R

examples/stm32/f1/waveshare-open103r/usbserial/echo.py

@@ -0,0 +1,16 @@
+#! /usr/bin/python
+
+import sys
+import serial
+
+def echo(text):
+    s = serial.Serial()
+    s.port = "/dev/ttyACM0"
+    s.open()
+    print s.read(s.write(text))
+
+if __name__ == "__main__":
+    if len(sys.argv) > 1:
+        echo(" ".join(sys.argv[1:]))
+    else:
+        print "Usage: sudo echo.py hello world"