Difference between revisions of "OPEN COM"

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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.
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The [[OPEN COM]] statement is used to access a computer's serial port COM.
  
  
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{{PageSyntax}}
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: '''OPEN''' "COMn: ''Speed'', ''Parity'', ''Bits'', ''Stopbit'', [''Options'']" [FOR {[[RANDOM]]|[[BINARY]]|[[OUTPUT]]|[[INPUT (file mode)|INPUT]]}] AS #''P'' [LEN = {{Parameter|byteSize}}]
  
{{PageSyntax}}
 
: [[OPEN]] "COMn: ''Speed'', ''Parity'', ''Bits'', ''Stopbit'', ['''Options''']" [FOR mode] AS #''P'' [LEN = ''bytesize'']
 
  
 
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{{PageParameters}}
* '''QB64''' can open any [[COM]] ''n'' port number. Qbasic could only open COM1 or COM2, but 3 and 4 could be swapped.
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* ''Speed'' (baud rate): 50, 150, 300, 600, 1200, 1800, 2400, '''9600''' (QBasic's maximum), 19200 or '''115200''' ('''QB64''''s maximum).
* See Windows System '''Device Manager''' for COM port numbers and port addresses &H3F8, &H2F8, &H3E8 and &H2E8.
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* ''Parity'': '''N''' (none), E (even), O (odd), S (space) or M (mark). Note: If 8 bits, use parity N for numerical data.
* 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'''
 
* ''Bits'' = number of bits/byte: Valid numbers: 5, 6, 7 or '''8'''
 
* ''Stopbit'' = number of stop bits: Valid numbers: '''1''', 1.5 or 2
 
* ''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|string]].(See list below)
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* Optional COM port ''Options'' (separated by commas):
* 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_MAC_OSX_versions|Keyword Not Supported in Linux or MAC versions]]
 
 
 
 
 
<center>'''Additional COM port Options (separated by commas)'''</center>
 
 
::* ASC : [[ASCII]] byte mode. End of line = [[CHR$]](13). End of file = CHR$(26)
 
::* 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).
 
::* 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 ignores a timeout. Default m = 1000 :''
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:: ''Below ms is the timeout in milliseconds 1 to 65535. Zero ignores a timeout. Default without ms = 1000 :''
::* CD[m] : Time until timeout of DCD (Carrier Detect) line in. CD0 ignores timeouts.
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::* CD[ms] : 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.
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::* CS[ms] : 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.
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::* DS[ms] : 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.
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::* OP[ms] : 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
 
::* 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
 
::* TB[b] : Size of transmit buffer in bytes when used. Default when not used = 512 bytes
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<center>'''Qbasic Description NOT Currently supported in QB64!'''</center>
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{{PageDescription}}
*[[INPUT (file mode)|INPUT]] mode can use [[INPUT (file statement)|INPUT #]] or [[INPUT$]]. [[OUTPUT]] mode can use [[PRINT (file statement)|PRINT #]] or [[PRINT USING (file statement)|PRINT #, USING]].
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* '''If any optional CD, CS, DS or OP timeouts occur the OPEN will fail or port access will stop. Try 0 to ignore.'''  
*[[RANDOM]] or [[BINARY|BIN]] modes can use [[INPUT (file statement)|INPUT #]], [[INPUT$]], [[PRINT (file statement)|PRINT #]], [[GET]] or [[PUT]]. BIN cannot set a buffer size!
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* '''QB64''' can open any COM''n'' port number from 1 to 9.
* Note: If random use [[LEN]] = to set size of random buffer(default LEN = 128). Use multiples of 128 for larger buffers.
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* See Windows System '''Device Manager''' for COM port numbers and port addresses &H3F8, &H2F8, &H3E8 and &H2E8.
* NOTE: NT or XP computers need a program like [http://www.beyondlogic.org/porttalk/porttalk.htm PortTalk] to access COM or other ports with Qbasic only!
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* Four commas are required after the Speed, Parity, Bits, and Stopbit, even if none of the Options are used.
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* 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).  
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* '''Currently, QB64 only supports [[OPEN]] FOR [[RANDOM]] access using the [[GET]]/[[PUT]] commands in [[BINARY|BIN]] mode.'''
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* '''Use the BIN option listed below for [[BINARY]] byte mode port access.'''
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* The [[LEN]] statement is also optional. The default record size is 512 bytes when not used.
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* Use the [[LOC]](portnumber) function to determine that there is data in the receive buffer when the value is greater than 0.
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* OPEN AS number can use a [[FREEFILE]] value. Numbers used by files already open '''cannot''' be used by OPEN COM.
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* [[Keywords_currently_not_supported_by_QB64#Keywords_Not_Supported_in_Linux_or_MAC_OSX_versions|Keyword Not Supported in Linux or MAC versions]]
  
  
''Example 1:'' Checking to see if a COM port exists. If the port does not exist Qbasic will cause a Windows access error!
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{{PageExamples}}
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''Example 1:'' Checking to see if a COM port exists. If the port does not exist QBasic will cause a Windows access error.
 
{{CodeStart}} '' ''
 
{{CodeStart}} '' ''
 
{{Cl|ON ERROR}} {{Cl|GOTO}} Handler  
 
{{Cl|ON ERROR}} {{Cl|GOTO}} Handler  
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{{Cl|RESUME}} {{Cl|NEXT}}  
 
{{Cl|RESUME}} {{Cl|NEXT}}  
 
{{CodeEnd}}
 
{{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!
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: ''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.
  
  
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''See also:''  
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''Example 3:'' Sending string data from one COM port to another requires predefined length strings:
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{{CodeStart}} '' ''
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{{Cl|DIM}} {{Cl|SHARED}} ByteIn {{Cl|AS}} {{Cl|STRING}} * 1 'One byte transfers
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{{Cl|DIM}} {{Cl|SHARED}} Byte4 {{Cl|AS}} {{Cl|STRING}} * 4 'Four byte transfers
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Byte4 = {{Cl|CHR$}}(254) + {{Cl|CHR$}}(175) + {{Cl|CHR$}}(0) + {{Cl|CHR$}}(3) 'Command code to query all 4 banks of switch input board.
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{{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.
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{{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.
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{{Cl|PUT}} #1, , Byte4 'Send the 4 byte command.
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Start# = {{Cl|TIMER}}
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{{Cl|DO...LOOP|DO}} {{Cl|UNTIL}} {{Cl|LOC}}(2) <> 0 'Check if there is data received at com2
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    {{Cl|IF...THEN|IF}} {{Cl|TIMER}} - Start# > .5 {{Cl|THEN}} {{Cl|EXIT DO}} 'Exit loop if no data arrives within .5 seconds.
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{{Cl|LOOP}}
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{{Cl|IF...THEN|IF}} {{Cl|LOC}}(2) = 0 {{Cl|THEN}} 'If no data was received.....
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    {{Cl|PRINT}} "No data received from COM port."
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    {{Cl|END}}
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{{Cl|END IF}}
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{{Cl|PRINT}} "Received from COM2:";
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{{Cl|DO...LOOP|DO}} {{Cl|UNTIL}} {{Cl|LOC}}(2) = 0 'Read data from COM2 until there is no more data.
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    {{Cl|GET}} #2, , ByteIn
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    {{Cl|PRINT}} {{Cl|ASC}}(ByteIn);
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{{Cl|LOOP}}
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{{Cl|END}} '' ''
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{{CodeEnd}}{{small|Code courtesy of forum member Hydrofoiler}}
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 +
 
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{{PageSeeAlso}}
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* [[BINARY]], [[RANDOM]]
 
* [[INPUT$]], [[PRINT (file statement)|PRINT #]]
 
* [[INPUT$]], [[PRINT (file statement)|PRINT #]]
 
* [[LOC]], [[INKEY$]], [[OPEN]]
 
* [[LOC]], [[INKEY$]], [[OPEN]]
 
* [[GET|GET #]], [[PUT|PUT #]]
 
* [[GET|GET #]], [[PUT|PUT #]]
* [[Port Access Libraries]] {{text|(COM or LPT registers)}}
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* [[Port Access Libraries]] {{text|(Includes full LPT and COM port descriptions with downloadable DLL library)}}
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* [[Windows_Libraries#Windows_Ports|Enumerating Windows Ports]]
  
  
 
{{PageNavigation}}
 
{{PageNavigation}}

Latest revision as of 12:44, 17 February 2021

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 MAC 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 forum member Hydrofoiler


See also



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