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You can use LPRINT in an OPL program to send information from the serial port (for printing or otherwise). OPL provides more advanced formatting features and printing control using Printer OPX, see Printer.opx — Printer and text handling.
It is also possible to read information from the serial port.
Section Contents
In your OPL program, set up the port with the statement LOPEN "TTY:A".
Now LPRINT should send information down the serial link lead for example, to an attached printer. If it does not, the serial port settings are not correct.
LOPEN "TTY:A" opens the serial port with the following default characteristics:
9600 baud
no parity
8 data bits
1 stop bit
RTS handshaking.
If your printer (or other device) does match these characteristics, the LOPEN statement sets the port up correctly, and subsequent LPRINT statements will print there successfully.
If your printer does not match these characteristics, you must use a procedure like the one listed below to change the characteristics of the serial port, before LPRINTs will print successfully to your printer.
Printers very often use DSR (DSR/DTR) handshaking, and you may need to set the port to use this.
The rsset: procedure listed below provides a convenient way to set up the serial port.
Each time you use an LOPEN "TTY:" statement, follow it with a call to the rsset: procedure. Otherwise the LOPEN will use the default characteristics.
Pass the procedure the values for the five port characteristics, like this:
rsset:(baud%,parity%,data%,stop%,hand%,&0)
The final parameter, which should be &0 here, is only used when reading from the port.
To find the value you need for each characteristic, use the tables below. You must give values to all five parameters, in the correct order.
Baud
|
Baud |
50 |
75 |
110 |
134 |
150 |
300 |
600 |
1200 |
1800 |
2000 |
2400 |
3600 |
4800 |
7200 |
9600 |
19200 |
|
value |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
Parity
|
Parity |
NONE |
EVEN |
ODD |
|
value |
0 |
1 |
2 |
Data bits
5, 6, 7 or 8
Stop bits
2 or 1
Handshaking
|
Handshaking |
ALL |
NONE |
XON |
RTS |
XON+RTS |
DSR |
XON+DSR |
RTS+DSR |
|
value |
11 |
4 |
7 |
0 |
3 |
12 |
15 |
8 |
PROC rsset:(baud%,parity%,data%,stop%,hand%,term&)
LOCAL frame%,srchar%(6),dummy%,err%
frame%=data%-5
IF stop%=2 :frame%=frame% OR 16 :ENDIF
IF parity% :frame%=frame% OR 32 :ENDIF
srchar%(1)=baud% OR (baud%*256)
srchar%(2)=frame% OR (parity%*256)
srchar%(3)=(hand% AND 255) OR $1100
srchar%(4)=$13
POKEL ADDR(srchar%(5)),term&
err%=IOW(-1,7,srchar%(1),dummy%)
IF err% :RAISE err% :ENDIF
ENDP
Take care to type this program in exactly as it appears here.
PROC test:
PRINT "Testing port settings"
LOPEN "TTY:A"
LOADM "rsset"
rsset:(8,0,8,1,0,&0)
LPRINT "Port OK" :LPRINT
PRINT "Finished" :GET
LCLOSE
ENDP
rsset:(8,0,8,1,0,&0) sets 1200 Baud, no parity, 8 data bits, 1 stop bit, and RTS/CTS handshaking.
The section of the rsset: procedure which actually sets the port is this:
srchar%(1)=baud% OR (baud%*256)
srchar%(2)=frame% OR (parity%*256)
srchar%(3)=(hand% AND 255) OR $1100
srchar%(4)=$13
POKEL ADDR(srchar%(5)),term&
err%=IOW(-1,7,srchar%(1),dummy%)
IF err% :RAISE err% :ENDIF
The elements of the array srchar% contain the values specifying the port characteristics. If you want to write a shorter procedure, you could work out what these values need to be for a particular setup you want, assign these values to the elements of the array, and then use the IOW function (followed by the error check) exactly as above.
If you need to read from the serial port, you must also pass a parameter specifying terminating mask for the read function. If term& is not supplied, the read operation terminates only after reading exactly the number of bytes requested. In practice, however, you may not know exactly how many bytes to expect and you would therefore request a large maximum number of bytes. If the sender sends less than this number of bytes altogether, the read will never complete.
The extra parameter, term& , allows you to specify that one or more characters should be treated as terminating characters. The terminating character itself is read into your buffer too, allowing your program to act differently depending on its value.
The 32 bits of term& each represent the corresponding ASCII character that should terminate the read. This allows any of the ASCII characters 1 to 31 to terminate the read.
For example, to terminate the read when Control-Z (i.e. ASCII 26) is received, set bit 26 of term&. To terminate on Control-Z or <CR> or <LF> which allows text to be read a line at a time or until end of file set the bits 26, 10 and 13. In binary, this is:
0000 0100 0000 0000 0010 0100 0000 0000
Converting to a long integer gives &04002400 and this is the value to be passed in term& for this case.
This example assumes that each line sent has maximum length 255 characters and is terminated by a <CR> and that Control-Z signals the end of all the data.
PROC testread:
LOCAL ret%,pbuf&,pbuf1&,buf$(255),end%,len%
PRINT "Test reading from serial port"
LOPEN "TTY:A"
LOADM "rsset" REM receive at 2400 without h/shake
rsset:(11,0,8,1,0,&04002000) REM Control-Z or CR
pbuf&=ADDR(buf$)
DO REM read max 255 bytes, after leading count byte
len%=255
pbuf1&=pbuf&+1
ret%=IOW(-1,1,#pbuf1&,len%)
POKEB pbuf&,len% REM len% = length actually read
REM including terminator char
end%=LOC(buf$,CHR$(26)) REM non-zero for Control-Z
IF ret%<0 and ret%<>-43
BEEP 3,500
PRINT
PRINT "Serial read error: ";ERR$(ret%)
ENDIF
IF ret%<>-43 REM if received with terminator
POKEB pbuf&,len%-1 REM remove terminator
PRINT buf$ REM echo with CRLF
ELSE
PRINT buf$; REM echo without CRLF
ENDIF
UNTIL end%
PRINT "End of session" :PAUSE -30 :KEY
ENDP
In your OPL program, specify the destination file with an LOPEN statement like this:
LOPEN "D:\PRINT\MEMO"
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