program: ECHO485.C
  use    : echo485 [baudrate]
	   (1) must run on 7188
	   (2) default baudrate is 9600
  function description:
	   (1) echo any data on the 7188's COM2(RS485) to COM4.
	   (2) data come from COM4(end with CR(0x0d)) will be send to
	       COM2(RS485)(data in will be buffered,until receive 0x0d,
	       7188 will send out the buffered data.(if checksum enable,
	       will append checksum(2 bytes) after the data,before 0x0d.)
	   (3) press 'q'(not 'Q') to quit.
	   (4) press 's'(not 'S') to toggle checksum mode.
	       so 'q' and 's' will not be send to 485.
	   (5) default mode is checksum enable.
	   (6) protocal is 1 start bit,8 data bit,none parity,1 stop bit.

   [PC]<---------->[7188-0]<------------------+----->[7000's]
	RS232  (COM4)    (COM2)  RS485        |
		   [7188-1]<------------------+
			 (COM2/COM1) RS485
   NOTE: Use echo485 to (1)monitor data on RS485,(2)send command to 7000's
ÿ