Chapter 6 Application Programs
RS-232 Operation Using QuickBASIC
RS-232 Operation Using QuickBASIC
The following example shows how to send command instructions and receive command responses over the RS-232 interface using QuickBASIC.
RS-232 Operation Using QuickBASIC
CLS
LOCATE 1, 1
DIM cmd$(100), resp$(1000)
’Set up serial port for 9600 baud, even parity, 7 bits;
’Ignore Request to Send and Carrier Detect; Send line feed,
’enable parity check, reserve 1000 bytes for input buffer
OPEN "com1:9600,e,7,2,rs,cd,lf,pe" FOR RANDOM AS #1 LEN = 1000
’Put the multimeter into the remote operation mode
PRINT #1, ":SYST:REM"
’
’Query the multimeter’s id string
PRINT #1, "*IDN?" LINE INPUT #1, resp$
PRINT "*IDN? returned: ", resp$
’Ask what revision of SCPI the multimeter conforms to PRINT #1, ":SYST:VERS?"
LINE INPUT #1, resp$
PRINT ":SYST:VERS? returned: ", resp$
’Send a message to the multimeter’s display, and generate a beep PRINT #1, ":SYST:BEEP;:DISP:TEXT ’34401A’"
’Configure the multimeter for dc voltage readings,
’10 V range, 0.1 V resolution, 4 readings
PRINT #1, ":CONF:VOLT:DC 10,0.1;:SAMP:COUN 4" ’ Trigger the readings, and fetch the results PRINT #1, ":READ?"
LINE INPUT #1, resp$
PRINT ":READ? returned: ", resp$ END
192
Chapter 6 Application Programs
RS-232 Operation Using Turbo C
RS-232 Operation Using Turbo C
The following example shows how to program an AT personal computer for interrupt-driven COM port communications. SCPI commands can be sent to the Agilent 34401A and responses received for commands that query information. The following program is written in Turbo C and can be easily modified for use with Microsoft Quick C.
RS-232 Operation Using Turbo C
#include <bios.h> |
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#include <stdio.h> |
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#include <string.h> |
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#include <dos.h> |
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#include <conio.h> |
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#define EVEN_7 (0x18 | 0x02 | 0x04) |
/* Even parity, 7 data, 2 stop */ |
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#define ODD_7 |
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(0x08 | 0x02 | 0x04) |
/* Odd parity, 7 data, 2 stop */ |
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#define NONE_8 (0x00 | 0x03 | 0x04) |
/* None parity, 8 data, 2 stop */ |
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#define BAUD300 |
0x40 |
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#define BAUD600 |
0x60 |
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#define BAUD1200 0x80 |
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#define BAUD2400 0xA0 |
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#define BAUD4800 0xC0 |
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#define BAUD9600 0xE0 |
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/* 8250 UART Registers */ |
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#define COM |
0x3F8 |
/* COM1 base port address */ |
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#define THR |
COM+0 |
/* LCR bit 7 = 0 */ |
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#define RDR |
COM+0 |
/* LCR bit 7 = 0 */ |
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#define IER |
COM+1 |
/* LCR bit 7 = 0 */ |
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#define IIR |
COM+2 |
/* The rest are don’t care for bit 7 */ |
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#define LCR |
COM+3 |
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#define MCR |
COM+4 |
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#define LSR |
COM+5 |
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#define MSR |
COM+6 |
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Continued on next page > |
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Microsoft is a U.S. registered trademark of Microsoft Corporation. |
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Chapter 6 Application Programs
RS-232 Operation Using Turbo C
RS-232 Operation Using Turbo C (continued)
#define IRQ4_int |
0xC |
/* IRQ4 interrupt vector number */ |
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#define IRQ4_enab |
0xEF |
/* IRQ4 interrupt controller enable mask */ |
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#define INT_controller |
0x20 |
/* |
8259 Interrupt controller address */ |
#define End_of_interrupt |
0x20 |
/* |
Non-specific end of interrupt command */ |
void interrupt int_char_in(void); void send_ctlc(void);
#define INT_BUF_size 9000
char int_buf[INT_BUF_size], *int_buf_in = int_buf, *int_buf_out = int_buf; unsigned int int_buf_count = 0;
unsigned char int_buf_ovfl = 0;
int main(int argc, char *argv[])
{
void interrupt (*oldvect)(); char command[80], c;
int i;
oldvect = getvect(IRQ4_int); |
/* Save old interrupt vector */ |
setvect(IRQ4_int,int_char_in); |
/* Set up new interrupt handler */ |
bioscom(0,BAUD9600 | EVEN_7,0); |
/* Initialize settings for COM1 */ |
outportb(MCR,0x9); |
/* Enable IRQ buffer, DTR = 1 */ |
outportb(IER,0x1); |
/* Enable UART data receive interrupt */ |
/* Enable IRQ4 in 8259 interrupt controller register */ outportb(INT_controller+1,inportb(INT_controller+1) & IRQ4_enab);
do { if(int_buf_ovfl) {
printf("\nBuffer Overflow!!!\n\n"); int_buf_in = int_buf_out = int_buf; int_buf_count = int_buf_ovfl = 0;
}
Continued on next page >
194
Chapter 6 Application Programs
RS-232 Operation Using Turbo C
RS-232 Operation Using Turbo C (continued)
printf("\nEnter command string:\n"); |
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gets(command); strcat(command,"\n"); |
/* SCPI requires line feed */ |
if(command[0] == 0x19) send_ctlc(); |
/* If ^Y then send ^C */ |
else if(command[0] != ’q’) { |
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for(i=0; i<strlen(command); i++) { |
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/* Wait for DSR and transmitter hold register empty */ while(!(inportb(LSR) & inportb(MSR) & 0x20)) ;
outportb(THR,command[i]); |
/* Send character */ |
} |
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} |
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if(strpbrk(command,"?")) { |
/* If query then get response */ |
c = 0; |
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do { |
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while(int_buf_count && !kbhit()) { |
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putch(c = *int_buf_out++); int_buf_count--;
if(int_buf_out >= int_buf + INT_BUF_size) int_buf_out = int_buf;
}
if(kbhit()) |
{ |
if(getch() |
== 0x19) send_ctlc(); /* if ^Y then send ^C */ |
c = 0xa; |
/* Terminate loop */ |
} |
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}
while(c != 0xa);
} |
/* End if */ |
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} |
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while(command[0] != ’q’); |
/* ’q’ to quit program */ |
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outportb(IER,inportb(IER) & 0xfe); |
/* Disable UART interrupt */ |
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outportb(MCR,0x1); |
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/* Disable IRQ buffer, DTR = 1 */ |
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/* Disable IRQ4 in 8259 interrupt controller register */ |
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outportb(INT_controller+1,inportb(INT_controller+1) | ~IRQ4_enab); |
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setvect(IRQ4_int,oldvect); |
/* Restore old interrupt vector */ |
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return(0); |
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} |
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Continued on next page >
195
Chapter 6 Application Programs
RS-232 Operation Using Turbo C
RS-232 Operation Using Turbo C (continued)
void interrupt int_char_in(void) |
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{ |
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enable(); |
/* Enable hardware interrupts */ |
if(int_buf_count < INT_BUF_size) { |
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*int_buf_in++ = inportb(RDR); |
/* Read byte from UART */ |
int_buf_count++; |
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if(int_buf_in >= int_buf + INT_BUF_size) int_buf_in = int_buf; |
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int_buf_ovfl = 0; |
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} |
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else { |
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inportb(RDR); |
/* Clear UART interrupt */ |
int_buf_ovfl = 1; |
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} |
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outportb(INT_controller,End_of_interrupt); |
/* Non-specific EOI */ |
} |
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void send_ctlc(void)
{
outportb(MCR,0x8);
delay(10); while(!(inportb(LSR) & 0x20)) ; outportb(THR,0x3); while(!(inportb(LSR) & 0x40)) ;
int_buf_in = int_buf_out = int_buf; int_buf_count = int_buf_ovfl = 0; delay(20);
outportb(MCR,0x9);
}
/* De-assert DTR */
/* Wait 10 mS for stray characters */ /* Wait on transmitter register */ /* Send ^C */
/* Wait for ^C to be sent */ /* Clear int_char_in buffer */
/* 20mS for 34401 to clean up */ /* Assert DTR */
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7
7
Measurement
Tutorial