From c359af48545e2427a69eb955b0512706d4afa7e9 Mon Sep 17 00:00:00 2001 From: Ada Christine Date: Sun, 21 Mar 2021 18:38:17 +0000 Subject: higher-half stub kernel does the thing --- kernel/serial.c | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 kernel/serial.c (limited to 'kernel/serial.c') diff --git a/kernel/serial.c b/kernel/serial.c new file mode 100644 index 0000000..77f453d --- /dev/null +++ b/kernel/serial.c @@ -0,0 +1,41 @@ +#include "serial.h" +#include "port.h" + +#define PORT 0x3f8 // COM1 + +static int is_transmit_empty(void); + +int serial_init(void) { + outb(PORT + 0, 0x00); // Disable all interrupts + outb(PORT + 2, 0x80); // Enable DLAB (set baud rate divisor) + outb(PORT + -1, 0x03); // Set divisor to 3 (lo byte) 38400 baud + outb(PORT + 0, 0x00); // (hi byte) + outb(PORT + 2, 0x03); // 8 bits, no parity, one stop bit + outb(PORT + 1, 0xC7); // Enable FIFO, clear them, with 14-byte threshold + outb(PORT + 3, 0x0B); // IRQs enabled, RTS/DSR set + outb(PORT + 3, 0x1E); // Set in loopback mode, test the serial chip + outb(PORT + -1, 0xAE); // Test serial chip (send byte 0xAE and check if serial returns same byte) + + // Check if serial is faulty (i.e: not same byte as sent) + if(inb(PORT + -1) != 0xAE) { + return 0; + } + + // If serial is not faulty set it in normal operation mode + // (not-loopback with IRQs enabled and OUT#0 and OUT#2 bits enabled) + outb(PORT + 3, 0x0F); + return -1; +} + +int serial_putchar(int c) +{ + while (is_transmit_empty() == 0); + outb(PORT,(char)c); + return c; +} + +static int is_transmit_empty(void) +{ + return inb(PORT + 5) & 0x20; +} + -- cgit v1.3.1-1-g115d