Access Balance Standalone Program

Version:    1.0 (for DOS)
                                              
Files:      fgscale.c (main), 
            fgscale.h,                               
            mettler.c, 
            sartorius.c, 
            getopt.c
	    scale16.exe (executable)
	    readme.txt
                          
Date:       January 6, 1999

Description:

      This program is to read the weight of clod on balance. The balance is hooked up
to PC computer through serial port. The communication protocol between PC and balance
is dependent on the different model and type of balance, so the communication module 
for balance is created from separate files. Currently, this package includes modules 
for balances of Mettler PM300 and Sartorius LC420. The operator can select balance 
(default Mettler), port (default COM2), unit (default gram), and measured range 
(default 1 - 5). The weight value will be recorded in a file (default filename 
"weight.dat"). The operator can give the file name on the command line. For the 
inquiry of usage, enter /?, followed the executable command.

Compiler:

      Watcom C_C++ version 10.6.

Operation:

      The main program contains the parameter selections for the command line which 
include:

	/b balance:	m for Mettler scale (default), and s for Sartorius scale;
	/c port #:	1, 2, 3, and 4 for COM1, COM2 (default), COM3, and COM4, 
                        respectively;
	/f file:	user's filename for weight record (default weight.dat);
	/u unit:	weight unit (default grams);
	/L bound #:	lower bound for weight (default 1);
	/U bound #:	upper bound for weight (default 5).

These parameters selected follow the command line. After hit the return key, the 
display is as follows:

-----------------------------------------------------------------------------
|       OPERATING INSTRUCTIONS:                                             |
|                                                                           |
|       1. Put clod on scale. The unit is g.                                |
|       2. Enter the can number.                                            |
|       3. Press <enter>, and wait for weight.                              |
|               (clod must weigh between 1.00 and 5.00 (g))                 |
|                                                                           |
|       To quit press 'q' or <esc>.                                         |
|                                               READY TO HIT ENTER KEY      |
-----------------------------------------------------------------------------

      After hit the return key, the PC prompt the user for sample #. Then hitting
the return key again, the sample number and weight value are displayed.

Configuration:

      The main program calls a function of get_mass corresponding to a specific 
balance which is hooked up to the PC on serial port. This function returns the value
of weight. There needs an individual module for a balance configuration. The 
initialization settings for the balances are put in fgscale.h file, so force the 
balances in the same settings:

             SETTINGS_1 (_COM_9600 | _COM_EVENPARITY | _COM_STOP1 | _COM_CHR7).
 
      For Mettler (PM300), the data format of balance interface is 1 start bit, 7
data bits, 1 parity bit, and the stop bit automatic (1 RX/2 TX). The balance
setting is:

             S.     ALL   (momentary value for data output, 
                          factory setting Stb: next stable value)
             b.     9600  (factory setting 2400 baud)  
             P.	    -E-   (factory setting even parity)		 
             PAUSE  1     (factory setting 1 second transfer rate to data receivers)
             AU	    off   (factory setting off)

The routine for interfacing Mettler PM300 first initializes the specified COM port
and settings as mentioned above, then enables the register of data available
interrupt. After pulsing the balance handshake line and sending a print command
(control word "ACK"), the routine goes into a loop to read characters from the
balance. During running in the loop, if getting an interrupt for a new charcter
available, the routine takes the character in the array. Otherwise, the routine
waits for the next character coming in until timeout break from the loop. If the
transmission errors happen associated with the COM port, the data from the balance
would be retransmitted. Because some unwanted spaces and possibly other unwanted
characters may be taken or 'D' is received if the data on balance is not stable, the
routine finally checks the characters received to strip the unwanted characters from
the array or retransmits the data if 'D' is found. The final correct string
transmitted is converted into the float type for the return value.

      For Sartorius (LC420), the data format of balance interface is the same as that
of Mettler PM300 except the stop bits (1 or 2) defined by user. The balance setting
is the factory settings except:

             9600 baud                     (code 517)
             Even parity                   (code 524)
             W/o stability for data output (code 611).

The routine for interfacing Satorius LC420 is the same as that for Mettler PM300
except the control word of "ESC P CR LF" and data stable sign which can be obtained
by ckecking wether the unit characters are received. If all the characters in
locations 12, 13 and 14 of the array are empty, the data is unstable.

Wiring Diagram for COM connector:

      The handshake modes both for Mettler and Sartorius are working in hardware
handshake. After the PC asserts DTR and sends a control command to the balances, the
balances transmit the weight data to the PC. There are a couple of wiring diagrams
for DTE device. The following are the COM wiring diagrams for Mettler PM300:

Diagrams of Figures 1(a) and (b) are provided by the manufacturer. Both diagrams 
are working properly by testing. The wiring diagram currently used (Figure 1(c)) 
is the one modified according to Figure 1(a). It also works well as follows:

	Mettler                                        "Standard" RS-232
	Connector                                      DB25 Connector
	----------------------------------------------------------------
	Description     Pin #                   Pin #  Description

	Brown Tx Data    12   ----------------->   3   RxD Input
	Green Rx Data     2   <-----------------   2   TxD Output

	White Signal     13   <---------------->   7   Signal Ground
	Ground
	
	Yellow handshake  3   <-----------------  20   DTR Output

                                          |<----   4   RTS
	                                  |---->   5   CTS
	                                  |---->   6   DSR
	                                  +---->   8   DCD
	----------------------------------------------------------------

                    (a) Connection between DB25 and DB25


	Mettler                                        "Standard" RS-232
	Connector                                      DB25 Connector
	----------------------------------------------------------------
	Description     Pin #                   Pin #  Description

	Brown Tx Data    12   ----------------->   3   RxD Input
	Green Rx Data     2   <-----------------   2   TxD Output

	White Signal     13   <---------------->   7   Signal Ground
	Ground
	
	Yellow handshake  3   <-----------------   4   RTS Output

                                          |<----  20   DTR
	                                  |---->   5   CTS
	                                  |---->   6   DSR
	                                  +---->   8   DCD
	----------------------------------------------------------------

                (b) Alternative connection between DB25 and DB25


	Mettler                                        "Standard" RS-232
	Connector                                      DB25 Connector
	----------------------------------------------------------------
	Description     Pin #                   Pin #  Description

	Brown Tx Data    12   ----------------->   3   RxD Input
	Green Rx Data     2   <-----------------   2   TxD Output

	White Signal     13   <---------------->   7   Signal Ground
	Ground
	
	Yellow handshake  3   <-----------|-----  20   DTR Output
                                          +---->   5   CTS

	----------------------------------------------------------------

                (c) Currently used connection between DB25 and DB25


                   Figure 1. Mettler Data-output Cable Digrams

The wiring diagrams for Sartorius scale are shown in Figure 2. The diagram currently 
used is Figure 2(b) for DB9 connector of COM.

	Sartorius                                      "Standard" RS-232
	DB25 Connector                                 DB25 Connector
	----------------------------------------------------------------
	Description     Pin #                   Pin #  Description

	TxD output        2   ----------------->   3   RxD Input
	RxD Input         3   <-----------------   2   TxD Output

	Ext. Signal       4   <----|----------->   7   Signal Ground
	Ground           14   <----+
	
	CTS Input         5   <-----------------  20   DTR Output

	DTR Output       20   ------------+---->   5   CTS Input
	                                  |---->   6   DSR
	                                  +---->   8   CD
	Chassis
	  Ground          1   <------ **               No connection
	----------------------------------------------------------------

                    (a) Connection between DB25 and DB25


	Sartorius                                      "Standard" RS-232
	DB25 Connector                                 DB9 Connector
	----------------------------------------------------------------
	Description     Pin #                   Pin #  Description

	TxD output        2   ----------------->   2   RxD Input
	RxD Input         3   <-----------------   3   TxD Output

	Ext. Signal       4   <----|----------->   5   Signal Ground
	Ground           14   <----+
	
	CTS Input         5   <-----------------   4   DTR Output

	DTR Output       20   ------------+---->   1   CD
	                                  |---->   6   DSR
	                                  +---->   8   CTS Input
	Chassis
	  Ground          1   <------ **               No connection
	----------------------------------------------------------------

                    (b) Connection between DB25 and DB9

	        Figure 2. Sartorius Data-output Cable Digrams
	
** CAble shield should be connected to one side only, usually the transmitting side.