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40 lines
1.6 KiB
40 lines
1.6 KiB
*Concepts you may want to Google beforehand: CPU timer, keyboard interrupts, scancode*
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**Goal: Implement our first IRQ handlers: the CPU timer and the keyboard**
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Everything is now ready to test our hardware interrupts.
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Timer
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-----
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The timer is easy to configure. First we'll declare an `init_timer()` on `cpu/timer.h` and
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implement it on `cpu/timer.c`. It is just a matter of computing the clock frequency and
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sending the bytes to the appropriate ports.
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We will now fix `kernel/utils.c int_to_ascii()` to print the numbers in the correct order.
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For that, we need to implement `reverse()` and `strlen()`.
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Finally, go back to the `kernel/kernel.c` and do two things. Enable interrupts again
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(very important!) and then initialize the timer interrupt.
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Go `make run` and you'll see the clock ticking!
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Keyboard
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--------
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The keyboard is even easier, with a drawback. The PIC does not send us the ASCII code
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for the pressed key, but the scancode for the key-down and the key-up events, so we
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will need to translate those.
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Check out `drivers/keyboard.c` where there are two functions: the callback and
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the initialization which configures the interrupt callback. A new `keyboard.h` was
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created with the definitions.
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`keyboard.c` also has a long table to translate scancodes to ASCII keys. For the time
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being, we will only implement a simple subset of the US keyboard. You can read
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more [about scancodes here](http://www.win.tue.nl/~aeb/linux/kbd/scancodes-1.html)
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I don't know about you, but I'm thrilled! We are very close to building a simple shell.
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In the next chapter, we will expand a little bit on keyboard input
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