{{fbdoc item="title" value="OPEN COM"}}----
Opens a serial port for input and output

{{fbdoc item="syntax"}}##
	[[KeyPgDeclare|declare]] [[KeyPgFunction|function]] **Open Com** ( byref //options// [[KeyPgAs|as]] [[KeyPgString|string]], **AS** //filenumber// [[KeyPgAs|as]] [[KeyPgLong|long]] ) [[KeyPgAs|as]] [[KeyPgLong|long]]
##
{{fbdoc item="usage"}}##
	//result// = **Open Com**( //options//[,] **AS**[#] //filenumber// )
##
{{fbdoc item="param"}}
	##//options//##
		A [[KeyPgString|string]] containing options used in controlling the port.
	##//filenumber//##
		The file number to bind to the port.

{{fbdoc item="ret"}}
	##**Open Com()**## returns a 32 bit ##[[KeyPgLong|Long]]##: a zero (##0##) on success and a non-zero error code otherwise.

{{fbdoc item="desc"}}
	This command opens a serial port of the PC, allowing to send and receive data by using the normal file commands as ##[[KeyPgPrintPp|Print  #]]##, ##[[KeyPgInputPp|Input #]]##, ##[[KeyPgGetfileio|Get #]]##, ...
	
	The main parameter is a ##[[KeyPgString|String]]## that describes, at the very least, which communications port to open. It has the format:
	
		##"**COM**//n//**:** [ //baudrate// ][ , [ //parity// ][ , [ //data_bits// ][ , [ //stop_bits// ][ , [ //extended_options// ]]]]]"##
	
	where,
	##//n//##
		Com port to open. ##"1"##, ##"2"##, ##"3"##, ##"4"##, etc.  Some platforms will support more serial ports depending on how the operating system is configured.  Where ##//n//## is not given, ##"COM:"## will map to ##"COM1:"##, except on Linux where ##"COM:"## maps to ##"/dev/modem"##
	##//baudrate//##
		##"300"## (default), ##"1200"##, ..., etc.
	##//parity//##
		##"N"## (none), ##"E"## (even, default), ##"O"## (odd), ##"S"## (space), ##"M"## (mark), ##"PE"## (QB-quirk: checked, even parity)
	##//data_bits//##
		##"5"##, ##"6"##, ##"7"## (default) or ##"8"##.
	##//stop_bits//##
		##"1"##, ##"1.5"## or ##"2"##. //(default value depends on baud rate and data bits, see table below)//
	
			{{table columns="2" cellpadding="2" cells="Condition;Default number of stop bits;baud rate <= 110 and data bits = 5;1.5;baud rate <= 110 and data bits >= 6;2;baud rate > 110;1"}}
	##//extended_options//##
		Miscellaneous options. //(See table below)//
	
			{{table columns="2" cellpadding="2" cells="Option;Action;'CSn';Set the CTS duration (in ms) (n>=0), 0 = turn off, default = 1000;'DSn';Set the DSR duration (in ms) (n>=0), 0 = turn off, default = 1000;'CDn';Set the Carrier Detect duration (in ms) (n>=0), 0 = turn off;'OPn';Set the 'Open Timeout' (in ms) (n>=0), 0 = turn off;'TBn';Set the 'Transmit Buffer' size (n>=0), 0 = default, depends on platform;'RBn';Set the 'Receive Buffer' size (n>=0), 0 = default, depends on platform;'RS';Suppress RTS detection;'LF';Communicate in ASCII mode (add LF to every CR) - Win32 doesn't support this one;'ASC';same as 'LF';'BIN';The opposite of LF and it'll always work;'PE';Enable 'Parity' check;'DT';Keep DTR enabled after CLOSE;'FE';Discard invalid character on error;'ME';Ignore all errors;'IRn';IRQ number for COM (only supported (?) on DOS)"}}
	
	All items except for the COM port are optional. The order of ##//baudrate//##, ##//parity//##, ##//data_bits//##, ##//stop_bits//## is fixed. Any skipped fixed item ( ##//baudrate//##, etc...) must be empty.
	
	The error code returned by ##**Open Com**## can be checked using ##[[KeyPgErr|Err]]## in the next line. The function version of  ##**Open Com**## returns directly the error code as a 32 bit ##[[KeyPgLong|Long]]##.

{{fbdoc item="ex"}}
{{fbdoc item="filename" value="examples/manual/fileio/opencom1.bas"}}%%(freebasic)
OPEN COM "COM1:9600,N,,2" as 1
%%
	Opens COM1 with 9600 baud, no parity, 7 data bits and 2 stop bits.

{{fbdoc item="filename" value="examples/manual/fileio/opencom2.bas"}}%%(freebasic)
OPEN COM "COM1:115200" as 1
%%
	Opens COM1 with 115200 baud, "even" parity, 7 data bits and 1 stop bits. 

{{fbdoc item="target"}}
	- On the Windows platform ##"COM:"## maps to ##"COM1:"##
	- On the Linux platform
		##"COM:"## maps to ##"/dev/modem"##
		##"COM1:"## maps to ##"/dev/ttyS0"##
		##"COM2:"## maps to ##"/dev/ttyS1"##, etc 
		##"/dev/xyz:"## maps to ##"/dev/xyz"##, etc
	- The DOS serial driver is experimental and can access COM ports 1 to 4 
		It uses the following base io and IRQ's as default: 
		COM1 - &h3f8 - IRQ4 
		COM2 - &h2f8 - IRQ3 
		COM3 - &h3e8 - IRQ4 
		COM4 - &h2e8 - IRQ3 
		An alternate IRQ can be specified using the the ##"IR//n//"## protocol option where ##//n//## is ##3## through ##7##.
		Currently not supported: IRQ's on the slave PIC, alternate base I/O addresses, Timeouts and most errors as detected in QB, hardware flow control, FIFO's.
		##"COM:"## maps to ##"COM1:"##
{{fbdoc item="lang"}}
	- In the //[[CompilerOptlang|-lang qb]]// dialect the old syntax ##OPEN "COMx:...## is supported. 

{{fbdoc item="diff"}}
	- In QB the syntax was ##OPEN  "COMx:[baudrate] [,parity, [data_bits, [stop_bits, [extended_options]]]]"  FOR INPUT|OUTPUT|RANDOM AS [#] n##
	- In QB, only ##"COM1:"## and ##"COM2:"## are supported.  In ""FreeBASIC"", any correctly configured serial port may be used.

{{fbdoc item="see"}}
	- ##[[KeyPgOpen|Open]]##

{{fbdoc item="back" value="CatPgFile|File I/O Functions"}}