OPEN COM: Difference between revisions

Latest revision as of 22:55, 19 February 2024

The OPEN COM statement is used to access a computer's serial port COM.

Syntax

OPEN "COMn: Speed, Parity, Bits, Stopbit, [Options]" [FOR {RANDOM|BINARY|OUTPUT|INPUT}] AS #P [LEN = byteSize]

Parameters

Speed (baud rate): 50, 150, 300, 600, 1200, 1800, 2400, 9600 (QBasic's maximum), 19200 or 115200 (QB64's 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
Optional 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 ms is the timeout in milliseconds 1 to 65535. Zero ignores a timeout. Default without ms = 1000 :

CD[ms] : Time until timeout of DCD (Carrier Detect) line in. CD0 ignores timeouts.
CS[ms] : Time until timeout of CTS (Clear to Send) line in. CS0 ignores timeouts.
DS[ms] : Time until timeout of DSR (Data Set Ready) line in. DS0 ignores timeouts.
OP[ms] : Time until data lines become active. If timeout then OPEN fails, OP0 ignores timeouts.
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.

Description

If any optional CD, CS, DS or OP timeouts occur the OPEN will fail or port access will stop. Try 0 to ignore.
QB64 can open any COMn port number from 1 to 9.
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.
Other OPEN options are optional and in any order separated by commas within the OPEN command string.(See list below)
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.
Keyword not supported in Linux or macOS versions

Examples

Example 1: Checking to see if a COM port exists. If the port does not exist QBasic will cause a Windows access error.

ON ERROR GOTO Handler
FF = FREEFILE
comPort$ = "COM1:"                         'try a COM port number that does not exist
CONST comMode$ = "9600,N,8,1,CS0,DS0"      'Use 0 to avoid timeouts
OPEN comPort$ + comMode$ FOR RANDOM AS FF
IF errnum = 0 THEN PRINT "COM exists!

K$ = INPUT$(1)
END

Handler:
errnum = ERR
PRINT "Error:"; errnum
RESUME NEXT

Explanation: QB64 may create error 68 if COM is not found. Use a zero CD, CS, DS or OP timeout value to avoid COM timeouts.

Example 2: Opening a COM port with the BIN, CS0 and DS0 options in QB64.

DIM bytestr AS STRING * 1  'one byte transfers
INPUT "COM port number #", port$  'any COM port number available

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!"

Example 3: Sending string data from one COM port to another requires predefined length strings:

DIM SHARED ByteIn AS STRING * 1 'One byte transfers
DIM SHARED Byte4 AS STRING * 4 'Four byte transfers

Byte4 = CHR$(254) + CHR$(175) + CHR$(0) + CHR$(3) 'Command code to query all 4 banks of switch input board.

OPEN "COM1:115200,N,8,1,BIN,CS0,DS0" FOR RANDOM AS #1 'Open port used to send commands.
OPEN "COM2:115200,N,8,1,BIN,CS0,DS0" FOR RANDOM AS #2 'Open port used to receive commands.

PUT #1, , Byte4 'Send the 4 byte command.

Start# = TIMER
DO UNTIL LOC(2) <> 0 'Check if there is data received at com2
    IF TIMER - Start# > .5 THEN EXIT DO 'Exit loop if no data arrives within .5 seconds.
LOOP

IF LOC(2) = 0 THEN 'If no data was received.....
    PRINT "No data received from COM port."
    END
END IF

PRINT "Received from COM2:";

DO UNTIL LOC(2) = 0 'Read data from COM2 until there is no more data.
    GET #2, , ByteIn
    PRINT ASC(ByteIn);
LOOP
END

Code courtesy of Hydrofoiler

@@ Line 6: / Line 6: @@
-{{Parameters}}
+{{PageParameters}}
 * ''Speed'' (baud rate): 50, 150, 300, 600, 1200, 1800, 2400, '''9600''' (QBasic's maximum), 19200 or '''115200''' ('''QB64''''s maximum).
 * ''Parity'': '''N''' (none), E (even), O (odd), S (space) or M (mark). Note: If 8 bits, use parity N for numerical data.
@@ Line 25: / Line 25: @@
 {{PageDescription}}
+* '''If any optional CD, CS, DS or OP timeouts occur the OPEN will fail or port access will stop. Try 0 to ignore.'''
+* '''QB64''' can open any COM''n'' port number from 1 to 9.
+* 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.
+* Other [[OPEN]] ''options'' are optional and in any order separated by commas within the OPEN command [[STRING|string]].(See list below)
+* The optional FOR access ''mode'' can be [[OUTPUT]], [[INPUT (file mode)|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 [[BINARY|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.
+* '''[[Keywords currently not supported by QB64#Keywords_not_supported_in_Linux_or_macOS_versions|Keyword not supported in Linux or macOS versions]]'''
+{{PageExamples}}
+''Example 1:'' Checking to see if a COM port exists. If the port does not exist QBasic will cause a Windows access error.
+{{CodeStart}}
+{{Cl|ON ERROR}} {{Cl|GOTO}} Handler
+FF = {{Cl|FREEFILE}}
+comPort$ = "COM1:"                         'try a COM port number that does not exist
+{{Cl|CONST}} comMode$ = "9600,N,8,1,CS0,DS0"      'Use 0 to avoid timeouts
+{{Cl|OPEN}} comPort$ + comMode$ {{Cl|FOR...NEXT|FOR}} {{Cl|RANDOM}} {{Cl|AS}} FF
+{{Cl|IF...THEN|IF}} errnum = 0 {{Cl|THEN}} {{Cl|PRINT}} "COM exists!
+K$ = {{Cl|INPUT$}}(1)
+{{Cl|END}}
+Handler:
+errnum = {{Cl|ERR}}
+{{Cl|PRINT}} "Error:"; errnum
+{{Cl|RESUME}} {{Cl|NEXT}}
+{{CodeEnd}}
+: ''Explanation:'' QB64 may create error 68 if COM is not found. Use a zero CD, CS, DS or OP timeout value to avoid COM timeouts.
+''Example 2:'' Opening a COM port with the BIN, CS0 and DS0 options in '''QB64'''.
+{{CodeStart}}
+{{Cl|DIM}} bytestr {{Cl|AS}} {{Cl|STRING}} * 1  'one byte transfers
+{{Cl|INPUT}} "COM port number #", port$  'any COM port number available
+{{Cl|OPEN}} "COM" + port$ + ":9600,N,8,1,BIN,CS0,DS0" {{Cl|FOR (file statement)|FOR}} {{Cl|RANDOM}} {{Cl|AS}} #1
+{{Cl|DO}} 'main loop
+    'receive data in buffer when LOC > 0
+    {{Cl|IF}} {{Cl|LOC}}(1) {{Cl|THEN}}
+       {{Cl|GET}} #1, , bytestr
+       {{Cl|PRINT}} "[" + bytestr + "]";
+    {{Cl|END IF}}
+    'transmit (send)
+    k$ = {{Cl|INKEY$}}
+    {{Cl|IF}} {{Cl|LEN}}(k$) = 1 {{Cl|THEN}}
+       k = {{Cl|ASC (function)|ASC}}(k$)
+       {{Cl|IF}} k >= 32 {{Cl|THEN}}     'ignore control key codes
+           {{Cl|PRINT}} ">" + k$ + "<";
+           bytestr = k$: {{Cl|PUT}} #1, , bytestr
+       {{Cl|END IF}}
+    {{Cl|END IF}}
+{{Cl|LOOP}} {{Cl|UNTIL}} k$ = {{Cl|CHR$}}(27)
+{{Cl|CLOSE}} #1: {{Cl|PRINT}} "Finished!"
+{{CodeEnd}}
+''Example 3:'' Sending string data from one COM port to another requires predefined length strings:
+{{CodeStart}}
+{{Cl|DIM}} {{Cl|SHARED}} ByteIn {{Cl|AS}} {{Cl|STRING}} * 1 'One byte transfers
+{{Cl|DIM}} {{Cl|SHARED}} Byte4 {{Cl|AS}} {{Cl|STRING}} * 4 'Four byte transfers
+Byte4 = {{Cl|CHR$}}(254) + {{Cl|CHR$}}(175) + {{Cl|CHR$}}(0) + {{Cl|CHR$}}(3) 'Command code to query all 4 banks of switch input board.
+{{Cl|OPEN}} "COM1:115200,N,8,1,BIN,CS0,DS0" {{Cl|FOR...NEXT|FOR}} {{Cl|RANDOM}} {{Cl|AS}} #1 'Open port used to send commands.
+{{Cl|OPEN}} "COM2:115200,N,8,1,BIN,CS0,DS0" {{Cl|FOR...NEXT|FOR}} {{Cl|RANDOM}} {{Cl|AS}} #2 'Open port used to receive commands.
+{{Cl|PUT}} #1, , Byte4 'Send the 4 byte command.
+Start# = {{Cl|TIMER (function)|TIMER}}
+{{Cl|DO...LOOP|DO}} {{Cl|UNTIL}} {{Cl|LOC}}(2) <> 0 'Check if there is data received at com2
+    {{Cl|IF...THEN|IF}} {{Cl|TIMER (function)|TIMER}} - Start# > .5 {{Cl|THEN}} {{Cl|EXIT DO}} 'Exit loop if no data arrives within .5 seconds.
+{{Cl|LOOP}}
+{{Cl|IF...THEN|IF}} {{Cl|LOC}}(2) = 0 {{Cl|THEN}} 'If no data was received.....
+    {{Cl|PRINT}} "No data received from COM port."
+    {{Cl|END}}
+{{Cl|END IF}}
+{{Cl|PRINT}} "Received from COM2:";
+{{Cl|DO...LOOP|DO}} {{Cl|UNTIL}} {{Cl|LOC}}(2) = 0 'Read data from COM2 until there is no more data.
+    {{Cl|GET}} #2, , ByteIn
+    {{Cl|PRINT}} {{Cl|ASC (function)|ASC}}(ByteIn);
+{{Cl|LOOP}}
+{{Cl|END}}
+{{CodeEnd}}
+{{Small|Code courtesy of Hydrofoiler}}
+{{PageSeeAlso}}
+* [[BINARY]], [[RANDOM]]
+* [[INPUT$]], [[PRINT (file statement)|PRINT #]]
+* [[LOC]], [[INKEY$]], [[OPEN]]
+* [[GET|GET #]], [[PUT|PUT #]]
+* [[Port Access Libraries]]
+* [[Windows Libraries#Windows_Ports|Enumerating Windows Ports]]
+{{PageNavigation}}

OPEN COM: Difference between revisions

Latest revision as of 22:55, 19 February 2024

Contents

Syntax

Parameters

Description

Examples

See also

Navigation menu

OPEN COM: Difference between revisions

Latest revision as of 22:55, 19 February 2024

Syntax

Parameters

Description

Examples

See also

Navigation menu

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