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 Keyboard IRQ Help 
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Joined: Thu Dec 23, 2010 1:12 pm
Posts: 9
Post Keyboard IRQ Help
EDIT: I completely recoded my interrupt code and it works now.

I am currently developing a 32 bit C++ and assembly OS booted by grub 2. I have got as far as implementing the IDT, remapping the PIC and implementing test keyboard code. However, when I press a key I get IRQ 4(interrupt 36) instead of IRQ 1 and the cpu resets. I have debugged it in bochs and it seems to do a far jump to 246:000a during the iret instruction then resets. This is very strange because my code segment is 8 and my data segment is 16. Including the null segment, they are the only gdt selectors in the kernel.
My Keyboard code is here:
Code:
void kbd_isr()
{
  unsigned char scancode = inb(0x60);
  char tmp[5];
  itoa(scancode,tmp,10);
  puts(tmp);
}

and my irq/isr handler is here:
Code:
#include <screen.h>
#include <string.h>
#include <system.h>
#include <keyboard.h>

//extern "C" void pit_isr();

struct registers
{
    unsigned int ds;                  // Data segment selector
    unsigned int edi, esi, ebp, esp, ebx, edx, ecx, eax; // Pushed by pusha.
    unsigned int int_no, err_code;    // Interrupt number and error code (if applicable)
    unsigned int eip, cs, eflags, useresp, ss; // Pushed by the processor automatically.
}__attribute__((__packed__));

extern "C"
{
void isr_handler(struct registers regs)
{
  switch(regs.int_no)
  {
    case 33:
      kbd_isr();
      break;
    default:
      char tmp[3];
      itoa(regs.int_no,tmp,16);
      error((char *) "interrupt: 0x");
      error(tmp);   
  }
  if(regs.int_no > 31)
  {
  /*  if(regs.int_no == 39 || regs.int_no == 47)
  {
    puts("spurious7\n");
    outb(0x20,0x0B);
    if(inb(0x20) & 0x80)
    {
      if(regs.int_no == 47)
      {
   puts("spurious15\n");
   outb(0x20,0x20);
      }
      return;
    }
  }
  */
 
  if(regs.int_no >= 40)
    outb(0xA0,0x20);
  outb(0x20,0x20);
  }
}
}

My code is partly based on JamesM's tutorials, but modified a large amount.


Sat Jul 16, 2011 12:44 pm
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Site Admin

Joined: Fri Jul 24, 2009 10:02 pm
Posts: 247
Location: Las Vegas, NV, US
Post Re: Keyboard IRQ Help
Glad you fixed it!

So, for the benefit of others in the future, what was the problem?


Tue Aug 23, 2011 1:10 am
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Joined: Thu Dec 23, 2010 1:12 pm
Posts: 9
Post Re: Keyboard IRQ Help
Most of the idt code was In assembly and was almost incomprihensible so I rewrote it and did more of it in c++. It was much easier to understand and I wouldn't have been able to find the problem in the asm. I don't know what the problem was. The idt code must have not set up the isrs correctly and caused a #GP when called. I'm guessing the asm code didn't split the isr addresses properly.


Wed Aug 31, 2011 4:01 pm
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