OPEN COM

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Revision as of 23:52, 9 May 2011 by imported>Clippy
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The OPEN COM statement is used to access a computer's Serial port COM1 or COM2 address using an OPEN statement.


Syntax

OPEN "COMn: Speed, Parity, Bits, Stopbit, [Options]" [FOR mode] AS #P [LEN = bytesize]


  • QB64 can open any COM n port number. Qbasic could only open COM1 or COM2, but 3 and 4 could be swapped.
  • See Windows System Device Manager for COM port numbers and port addresses &H3F8, &H2F8, &H3E8 and &H2E8.
  • Four commas are required after the Speed, Parity, Bits, and Stopbit, even if none of the Options are used.
  • Speed(baud rate): 50, 150, 300, 600, 1200, 1800, 2400, 9600(QB max), 19200 or 115200(QB64 max) maximum.
  • Parity: N (none), E (even), O (odd), S (space) or M (mark). Note: If 8 bits use parity N for numerical data!
  • Bits = number of bits/byte: Valid numbers: 5, 6, 7 or 8
  • Stopbit = number of stop bits: Valid numbers: 1, 1.5 or 2
  • Other OPEN options are optional and in any order separated by commas within the OPEN command string.
  • The optional FOR access mode can be OUTPUT, INPUT or RANDOM (default mode when no FOR statement is used).
  • Currently, QB64 only supports OPEN FOR RANDOM access using the GET/PUT commands in BIN mode!
  • Use the BIN option listed below for BINARY byte mode port access!
  • The LEN statement is also optional. The default record size is 512 bytes when not used.
  • Use the LOC(portnumber) function to determine that there is data in the receive buffer when the value is greater than 0.
  • OPEN AS number can use a FREEFILE value. Numbers used by files already open cannot be used by OPEN COM!


Additional COM port Options (separated by commas)
* ASC : ASCII byte mode. End of line = CHR$(13). End of file = CHR$(26)
* BIN : Binary byte mode. Default mode if ASC is not used(option not required).
Below m is the timeout in milliseconds 1 to 65535. Zero is ignore timeout. Default m = 1000 :
CD[m] : Time until timeout of DCD (Carrier Detect) line in. CD0 ignores timeouts.
CS[m] : Time until timeout of CTS (Clear to Send) line in. CS0 ignores timeouts.
DS[m] : Time until timeout of DSR (Data Set Ready) line in. DS0 ignores timeouts.
OP[m] : Time until data lines become active. If timeout then OPEN fails! OP0 ignores timeouts.
If any timeouts occur the OPEN will fail or port access will stop!
RB[b] : Size of receive buffer in bytes when used. Default when not used = 512 bytes
TB[b] : Size of transmit buffer in bytes when used. Default when not used = 512 bytes
RS : Supress detection of Request to Send (RTS) line.


Qbasic Description NOT Currently supported in QB64!



Example: Opening a COM port with the BIN, CS0 and DS0 options in QB64.

INPUT "COM port number #", port$ 'any COM port number available DIM bytestr AS STRING * 1 'one byte transfers OPEN "COM" + port$ + ":9600,N,8,1,BIN,CS0,DS0" FOR RANDOM AS #1 DO 'main loop 'receive data in buffer when LOC > 0 IF LOC(1) THEN GET #1, , bytestr PRINT "[" + bytestr + "]"; END IF 'transmit (send) k$ = INKEY$ IF LEN(k$) = 1 THEN k = ASC(k$) IF k >= 32 THEN 'ignore control key codes PRINT ">" + k$ + "<"; bytestr = k$: PUT #1, , bytestr END IF END IF LOOP UNTIL k$ = CHR$(27) CLOSE #1: PRINT "Finished!


See also:



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