lesson 20 finished: timer + keyboard

Author: cfenollosa

20-interrupts-timer/README.md

@@ -34,3 +34,6 @@ created with the definitions.
 `keyboard.c` also has a long table to translate scancodes to ASCII keys. For the time
 being, we will only implement a simple subset of the US keyboard. You can read
 more [about scancodes here](http://www.win.tue.nl/~aeb/linux/kbd/scancodes-1.html)
+
+I don't know about you, but I'm thrilled! We are very close to building a simple shell.
+In the next chapter, we will expand a little bit on keyboard input

20-interrupts-timer/cpu/timer.c

@@ -9,7 +9,7 @@ static void timer_callback(registers_t regs) {
     tick++;
     kprint("Tick: ");
 
-    char *tick_ascii;
+    char tick_ascii[256];
     int_to_ascii(tick, tick_ascii);
     kprint(tick_ascii);
     kprint("\n");

20-interrupts-timer/drivers/keyboard.c

@@ -197,11 +197,14 @@ void print_letter(u8 scancode) {
             break;
         default:
             /* 'keuyp' event corresponds to the 'keydown' + 0x80 
-             * it may still be a scancode we haven't implemented yet */
-            if (scancode - 0x80 <= 0x39) {
+             * it may still be a scancode we haven't implemented yet, or
+             * maybe a control/escape sequence */
+            if (scancode <= 0x7f) {
+                kprint("Unknown key down");
+            } else if (scancode <= 0x39 + 0x80) {
                 kprint("key up ");
                 print_letter(scancode - 0x80);
-            } else kprint("Unknown");
+            } else kprint("Unknown key up");
             break;
     }
 }

20-interrupts-timer/kernel/kernel.c

@@ -6,7 +6,7 @@ void main() {
     isr_install();
 
     asm volatile("sti");
-//    init_timer(50);
+    init_timer(50);
     /* Comment out the timer IRQ handler to read
      * the keyboard IRQs easier */
     init_keyboard();