Code for the motor controller

This is basically what we used in Detroit.

Change-Id: If2820d7ec5fcbc5f33b4082025027a6e969ad0e1
diff --git a/motors/usb/usb_serial.h b/motors/usb/usb_serial.h
index 2512adc..40e7c36 100644
--- a/motors/usb/usb_serial.h
+++ b/motors/usb/usb_serial.h
@@ -56,7 +56,7 @@
 // Drops any unread input until the most recent packet sent.
 void usb_serial_flush_input(int port);
 
-// Writes data. Returns -1 if it times out or size if it succeeds.
+// Writes data. Returns -1 if it times out or 0 if it succeeds.
 //
 // NOTE: This does not send immediately. The data is buffered
 int usb_serial_write(int port, const void *buffer, uint32_t size);