Appendix

COM Ports and Serial Devices

Formats	1. Open Device in DOS: OPEN (chan[,fileopt])"port:" 2. Open Device in Windows: OPEN (chan,fileopt,OPT=string$)"port:" 3. Open Device in UNIX: OPEN (chan[,fileopt])dev_path$ Where
		chan		Channel or logical file number to assign to the file.
		dev_path$		Path to a UNIX device file.
		fileopt		File options. Supported options for opening a COM port include:
				BSZ=num Block size
				ERR=stmtref Error transfer
				ISZ=num Open file in binary mode NBF=num Dedicated number of buffers OPT=string$ Options for Windows only
				(See Windows OPT= Settings.)
		port:		Port ID; e.g., OPEN(1,settings$)"COM2:".
		string$		String defining the characteristics of the connection.
		stmtref		Program line number or statement label to which to transfer control.
Description	You can OPEN a COM port for direct serial communication and gain access to special serial devices, including: label printers, weigh scales, modems, and access card readers) Some devices, such as modems, involve two-way communications, where you can set up tasks such as background processes to monitor the port, with ACK-NAK and/or READ-do processing. Other devices, such as label printers, use one-way serial communication; e.g., in PRINT statements.
Format 1	Open Device in DOS   OPEN (chan[,fileopt])"port:"   When you OPEN a serial device in DOS, ProvideX uses the current DOS "mode" settings for the port.
Format 2	Open Device in Windows   OPEN (chan,fileopt,OPT=string$)"port:" Use this format in Windows to open a serial device for direct access. For Windows only, you can include OPT=string$; e.g., in OPEN (1,OPT=settings$)"COM2:", the string variable in the OPT= option contains settings for the attributes.
*Note*	If the OPT= option is omitted from the communications settings, ProvideX will default to the setup in the Windows Control Panel.
	Windows OPT= Settings The settings for the OPT= option use the following attributes and format. Note that flow_rate is optional. OPT="baud_rate,parity,data_bits,stop_bits[,flow_rate]" Where
	baud rate		Valid range is 300 to 115200
	data_bits		Use one of three valid values: 1, 7, or 8
	flow_rate		(Optional.) Valid values include: x for XON/XOFF software flow or p for RTS/CTS physical/hardware flow. (Omit the value for "none")
	parity char. Use one of three alpha characters: N for None, O for Odd parity, E for
			Even parity
	stop_bits		Use one of the valid values: -1 (minus one), 0 (zero), 1, 1.5, 2.
	Example: The setting$ assigned in the Windows example below are for the serial communications attributes: baud rate, parity (n=none), data bits (8), stop bit (1) and flow rate (xon/xoff switch).   12540 let setting$="9600,n,8,1,x" 12550 let printer=hfn 12560 open (printer,isz=1,opt=setting$,err=13000)"COM2:" 12570 print (printer)"Title"
Format 3	Open Device in UNIX   OPEN (chan[,fileopt])dev_path$ When you OPEN the serial device using this format in UNIX, the port is opened with the current characteristics. To change the settings, you can either set line characteristics at the OS level before starting ProvideX or use an INVOKE directive after you open the device:   invoke "stty 38400 -IXANY IXON IXOFF ... </dev/tty2A"
*Note*	WindX Tip. While it is possible to open a serial device on the client PC by using the [WDX] tag, we recommend against doing this. Instead, we advise you to use a CALL from the host to a [WDX] subprogram on the remote client PC. Design your subprogram to open and control the device and its settings. You can return your results to the host via your CALL's parameters. For more information see[WDX] Direct Action to Client Machine.
See Also	OPEN Directive