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Serial Port (RS232)
[Device Drivers]

Functions
void	rs232_handler (word port)
	RS232 common handler routine. Parameters: port  The serial port.
void	close_rs232 (word port)
	Close a specific RS232 port. Parameters: port  The port to close.
void	init_rs232 (word port, byte divisor)
	Initialize the RS232 interface with a bps rate. Parameters: port  The serial port to initialize. divisor  The divisor to set the bps rate (see serial.h).
byte	rs232_getchar ()
	Get a character from the current serial port. Returns: The ASCII code of the character read.
void	rs232_putchar (byte c)
	Write a character to the current serial port. Parameters: c  The ASCII code of the character to write.
void	rs232_task ()
	Get permanently characters from the serial port and print it to the screen. Note: This is no-exit function, you have to use it not as a simple procedure, but as a kernel-thread (see task.c).
void	rs232_chat (char *argv)
	Chat with a modem or a serial device. Parameters: argv  A string that contains the bps rate to initialize the serial port connection.
Variables
int	rs232_read_head = 0
	RS232 buffer for read operations :: head pointer.
int	rs232_read_tail = 0
	RS232 buffer for read operations :: tail pointer.
byte	rs232_read_buf [RS232_BUF_DIM]
	RS232 buffer for read operations.
int	rs232_write_head = 0
	RS232 buffer for write operations :: head pointer.
int	rs232_write_tail = 0
	RS232 buffer for write operations :: tail pointer.
byte	rs232_write_buf [RS232_BUF_DIM]
	RS232 buffer for write operations.
word	curr_port = COM1
	RS232 current port.

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Detailed Description

The RS232 COM-port driver.

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Function Documentation

void close_rs232 (  word    port )

Close a specific RS232 port. Parameters: port  The port to close. Definition at line 122 of file serial.c. { // Turn off rs232 interrupt // outportb(port+1, 0); // Disable the FIFO // outportb(port+2, 0); // Disconnect UART from the ICU // outportb(port+4, 0); }

void init_rs232 (  word    port, byte    divisor )

Initialize the RS232 interface with a bps rate. Parameters: port  The serial port to initialize. divisor  The divisor to set the bps rate (see serial.h). Definition at line 138 of file serial.c. { // Install the IRQ handler routine // if ( (port == COM1) || (port == COM3) ) install_irq_handler( RS232_1_IRQ, (void *)rs232_handler_port1 ); else if ( (port == COM2) || (port == COM4) ) install_irq_handler( RS232_2_IRQ, (void *)rs232_handler_port2 ); else return; // Turn off rs232 interrupt // outportb(port+1, 0); // Set DLAB on // outportb(port+3, 0x80); // Set baud rate - Divisor Latch Low Byte // outportb(port, divisor); // Set baud rate - Divisor Latch High Byte // outportb(port+1, 0x00); // 8 bits, no parity, 1 stop-bit // outportb(port+3, 0x03); // FIFO Control Register // outportb(port+2, 0xC7); // Turn on DTR, RTS and OUT2 // outportb(port+4, 0x0B); // Enable interrupts when data is received // outportb(port+1, 0x01); // Clear receiver // (void)inportb(port); // Clear line status // (void)inportb(port+5); // Clear modem status // (void)inportb(port+6); }

void rs232_chat (  char *    argv )

Chat with a modem or a serial device. Parameters: argv  A string that contains the bps rate to initialize the serial port connection. Definition at line 247 of file serial.c. { static char *default_bps = "38400"; task_t *child; word key; kprintf( "\n\rOpening RS232-1 interface (COM1)... " "\n\rPress CTRL-X to quit." ); if (strcmp(argv, "2400")==0) init_rs232(COM1, BPS_2400); else if (strcmp(argv, "4800")==0) init_rs232(COM1, BPS_4800); else if (strcmp(argv, "9600")==0) init_rs232(COM1, BPS_9600); else if (strcmp(argv, "19200")==0) init_rs232(COM1, BPS_19200); else if (strcmp(argv, "38400")==0) init_rs232(COM1, BPS_38400); else if (strcmp(argv, "56700")==0) init_rs232(COM1, BPS_56700); else if (strcmp(argv, "115200")==0) init_rs232(COM1, BPS_115200); else { // Default bps // argv = default_bps; init_rs232(COM1, BPS_38400); } kprintf("\n\rBitrate: %s bps", argv); child = create_process(&rs232_task, &rs232_task, 0, "rs232_task", KERNEL_PRIVILEGE); set_color(GREEN); kprintf("\r [ OK ]\n\r"); set_color(DEFAULT_COLOR); while(TRUE) { // Get a char from the keyboard // key = kgetchar(); if (key==CTRL_X) break; if ((key&0xFF)==13) rs232_putchar(10); // Write the char to the serial port // rs232_putchar(key); } // Local echo of the ESCape char // kputchar((byte)CTRL_X); // Kill the rs232 task // kill(child->pid); // Close RS232 connection // close_rs232(curr_port); kprintf("\n\rBye.\n\r"); }

byte rs232_getchar (    )

Get a character from the current serial port. Returns: The ASCII code of the character read. Definition at line 183 of file serial.c. { byte temp; dword IF = GET_IF(); // If the buffer is empty enable interrupts and wait... // while( rs232_read_head==rs232_read_tail ) { enable(); idle(); } disable(); // Update the RS232 buffer in mutual exclusion & get the char // temp = rs232_read_buf[rs232_read_head]; rs232_read_head = (rs232_read_head+1)%RS232_BUF_DIM; SET_IF(IF); return(temp); }

void rs232_handler (  word    port )

RS232 common handler routine. Parameters: port  The serial port. Definition at line 47 of file serial.c. { byte flag, ch; while(TRUE) { // Get a char from the serial port // flag = inportb(port+2); if (flag & 0x01) break; switch(flag & 0x06) { // Modem status - clear intr by reading modem status reg // case 0x00: (void)inportb(port+6); break; // Write char - Send the char to the serial port // case 0x02: if (rs232_write_head != rs232_write_tail) { ch = rs232_write_buf[rs232_write_head]; rs232_write_head = (rs232_write_head+1)%RS232_BUF_DIM; outportb(port, ch); } // Inhibit TX interrupts if write buffer is empty (leave RX enabled) // if (rs232_write_head == rs232_write_tail) outportb(port+1, 0x01); break; // Read char - Get the char from the serial port // case 0x04: while(TRUE) { // Check for data ready // flag = inportb(port+5); if (!(flag & 0x01)) break; // Get the character // ch = inportb(port); // Store it into the buffer if it is not full // if (((rs232_read_tail+1)%RS232_BUF_DIM) != rs232_read_head) { rs232_read_buf[rs232_read_tail] = ch; rs232_read_tail = (rs232_read_tail+1)%RS232_BUF_DIM; } } break; // Line status - clear intr by reading line status reg // case 0x06: (void)inportb(port+5); break; } } }

void rs232_putchar (  byte    c )

Write a character to the current serial port. Parameters: c  The ASCII code of the character to write. Definition at line 210 of file serial.c. { dword IF = GET_IF(); // Check if the write buffer is full // if (((rs232_write_tail+1)%RS232_BUF_DIM) == rs232_write_head) return; disable(); // Write the char to the buffer in mutual exclusion // rs232_write_buf[rs232_write_tail] = c; rs232_write_tail = (rs232_write_tail+1)%RS232_BUF_DIM; SET_IF(IF); // Enable RX & TX interrupts // outportb(curr_port+1, 0x03); }

void rs232_task (    )

Get permanently characters from the serial port and print it to the screen. Note: This is no-exit function, you have to use it not as a simple procedure, but as a kernel-thread (see task.c). Definition at line 235 of file serial.c. { while(TRUE) { kputchar(rs232_getchar()); } }

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Variable Documentation

word curr_port = COM1 [static]

RS232 current port. Definition at line 43 of file serial.c.

byte rs232_read_buf[RS232_BUF_DIM]

RS232 buffer for read operations. Definition at line 32 of file serial.c.

int rs232_read_head = 0 [static]

RS232 buffer for read operations :: head pointer. Definition at line 27 of file serial.c.

int rs232_read_tail = 0 [static]

RS232 buffer for read operations :: tail pointer. Definition at line 29 of file serial.c.

byte rs232_write_buf[RS232_BUF_DIM]

RS232 buffer for write operations. Definition at line 40 of file serial.c.

int rs232_write_head = 0 [static]

RS232 buffer for write operations :: head pointer. Definition at line 35 of file serial.c.

int rs232_write_tail = 0 [static]

RS232 buffer for write operations :: tail pointer. Definition at line 37 of file serial.c.

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