Serial implementation Pt1

Serial testing with COM1 works - need to rework I/O to have it output
tho. That's next.

include/kttools.h

@@ -7,6 +7,20 @@
 #define KTTOOLS_H
 #include <stdint.h>
 
+/**
+ * @brief Convert a hex int to string, up to 32 bits.
+ *
+ *  Converts int "num" into a null-terminated string, placed into buffer "buf".
+ *  Evaluates from right to left, so left hand digits will be cut off if the buffer is too small
+ *  Should work for non 32-bit integers actually, but is uint32_t for now.
+ *  
+ *  @param  num:    Value to convert to string
+ *  @param  buf:    Memory to place the string into
+ *  @param  size:   Size of the memory buffer
+ *  @param  radix:  Base counting system to use for output
+ *  @return No return value
+ *
+ */
 void i_to_str(uint32_t num, char* buf, int size, int radix);
 
 #endif

include/serial.h

@@ -0,0 +1,47 @@
+/*  serial.h
+*   Serial Interface
+*
+*   Send/receive data via serial ports.
+*/
+#ifndef SERIAL_H
+#define SERIAL_H
+#include "asm.h"
+#include <stdint.h>
+
+typedef struct SerialState_s {
+    uint16_t port;
+} SerialState_t;
+
+/**
+ * @brief Initialize a serial port for communication
+ * @param port The serial port number to initialize
+ * @return Status code indicating success or failure
+ */
+int serial_init(uint16_t port);
+
+/**
+ * @brief Check if there is pending data to receive on the serial port
+ * @return Non-zero if data is pending, 0 otherwise
+ */
+int serial_recv_pending();
+
+/**
+ * @brief Receive a single byte from the serial port
+ * @return The received byte as an 8-bit unsigned integer
+ */
+uint8_t serial_recv8(uint16_t port);
+
+/**
+ * @brief Check if the serial port is ready to send data
+ * @return Non-zero if ready to send, 0 otherwise
+ */
+int serial_send_pending(uint16_t port);
+
+/**
+ * @brief Send a single byte through the serial port
+ * @param data The 8-bit data byte to send
+ */
+int serial_send8(uint16_t port, char data);
+
+
+#endif

src/kttools.c

@@ -12,20 +12,6 @@
 
 
 
-/**
- * @brief Convert a hex int to string, up to 32 bits.
- *
- *  Converts int "num" into a null-terminated string, placed into buffer "buf".
- *  Evaluates from right to left, so left hand digits will be cut off if the buffer is too small
- *  Should work for non 32-bit integers actually, but is uint32_t for now.
- *  
- *  @param  num:    Value to convert to string
- *  @param  buf:    Memory to place the string into
- *  @param  size:   Size of the memory buffer
- *
- *  @return No return value
- *
- */
 void i_to_str(uint32_t num, char* buf, int size, int radix) {
     //null terminate the string
     if(num == 0){

src/main.c

@@ -1,32 +1,50 @@
 //Our own code, at this point...
-//#include <stddef.h>
+//Output table:
+//0: VGA
+//1: COM1
+#define OUTPUT_TYPE 1
 #include <stdint.h>
 #include "vga.h"
 #include "io.h"
 #include "kttools.h"
 #include "kmultiboot.h"
 #include "idt.h"
-//finally, main.
+#include "serial.h"
 void kern_main(uint32_t multiboot_magic, mb_info_t* multiboot_info)
 {
     //Hello C! Let's get to work in cleaning up our environment a bit and creating some safety.
     //First interrupts.
     setup_idt();
  
-    //wipe the screen
+    //Let's pick an output schema.
+    int (*outWriter)(char) = 0;
+    int comstatus = 1234;
+    switch(OUTPUT_TYPE) {
+        case 1:
+            comstatus = serial_init(COM1);
+            if(comstatus) {
+                //Fail...
+                break; 
+            }
+            outWriter = serial_send8;
+            break;
+    }
+    //VGA is selected or the selected option failed, falling back 
+    if(outWriter == 0){
+        outWriter = vga_out;
         vga_clear();
-
-    printf(vga_out, "Entry eax:%X\n", multiboot_magic);
-
-    if(multiboot_magic != 0x2BADB002) {
-        println(vga_out, "Bootloader not multiboot1 compliant! Needed for mmap, etc. Can't work without it, kthxbye!");
-        return;
-    } else {
-        println(vga_out, "Multiboot detected! Continuing...");
     }
 
-    printf(vga_out, "MEM_LOWER:%X\n", multiboot_info->mem_lower);
+    printf(outWriter, "Entry eax:%X\n", multiboot_magic);
-    printf(vga_out, "MEM_UPPER:%X\n", multiboot_info->mem_upper);
 
+    if(multiboot_magic != 0x2BADB002) {
+        println(outWriter, writerState, "Bootloader not multiboot1 compliant! Needed for mmap, etc. Can't work without it, kthxbye!");
+        return;
+    } else {
+        println(outWriter, writerState, "Multiboot detected! Continuing...");
+    }
+
+    printf(outWriter, writerState, "MEM_LOWER:%X\n", multiboot_info->mem_lower);
+    printf(outWriter, writerState"MEM_UPPER:%X\n", multiboot_info->mem_upper);
 }
 

src/serial.c

@@ -0,0 +1,60 @@
+#include "serial.h"
+#include <stdint.h>
+
+
+int serial_init(uint16_t port) {
+    //disable interrupts when messing with it
+    outb(port + 1, 0x00);
+    //set the dlab latch in order to make the baud rate accessible. In binary for clarity.
+    outb(port + 3, 0b10000000);
+    
+    //Sets the baud rate. Quick except on baud rate:
+    //internal clock for the serial controller is 115200 ticks/sec. Or 115200hz. 
+    //This value we set, the "clock divisor", will check it every x ticks.
+    //So for example, if we wanted to check it every second, we'd want a divisor of 115200. Or, to check it as fast as possible, 1.
+    //Higher baud rates however equate to more error, so keep the divisor high. 
+    //In ourcase, the osdev wiki uses 3 for the divisor, or 38400 baud, and we will go with this example until further notice.
+    //(Source:https://wiki.osdev.org/Serial_Ports#Baud_Rate)
+
+    //Baud lo byte
+    outb(port, 0x03);
+    //Baud hi byte
+    outb(port+1, 0x00);
+
+    //Again from OSWiki we're going to use their defaults for now.
+    //DLAB off
+    //Parity=0(no Parity)
+    //One stop bit (set to 0)
+    //Transmit in units of 8 bits
+    outb(port+3, 0b00000011);
+
+    //FIFO Control register
+    //14 bit threshold for interrupt trigger
+    //flush and enable FIFOs.
+    outb(port+2, 0b11000111);
+
+    //Enable IRQs + DTR + RTS
+    //Nicely explained here: https://stackoverflow.com/questions/957337/what-is-the-difference-between-dtr-dsr-and-rts-cts-flow-control
+    //In the future, this will be referred to 0x0B.
+    outb(port+4, 0b00001011);
+
+    //done! Let's test our chip. put it in loopback mode.
+    outb(port+4, 0x1E);
+    //Lets try sending C4 (boom!) to test it
+    outb(port, 0xC4);
+    
+    if(inb(port) != 0xC4) {
+        //Boo womp
+        return 1;
+    }
+
+    //we're good! All set up. Lets put it back into normal operational mode and gtfo.
+    outb(port+4, 0x0B);
+    return 0;
+
+}
+
+int serial_send_pending(uint16_t port) {
+    //Bit 5 of the line status register has our output queue, essentially
+    return !(inb(port + 5) & 0x20);
+}