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Thanks for your reply. In short term I just want to learn how to do this. In long term I'm hoping to read in visual input from a camera or something. Do you know of any tutorials for GPIOs or any tutorials to do with input/outputCombuster wrote:The only digital GPIO you'll find on a PC is the oldfashioned parallel port. I've never bothered with that thing but it will probably look pretty close to the GPIOs you find in all sorts of other devices.
I did see something about the keyboard and 0x60 about 10 minutes ago. You can use the out instruction for outputting to hardware right? and input instructionCasm wrote:The x86's in and out instructions are conceptually similar to programming a port on a microcontroller. Port numbers on a PC don't actually correspond to pins on the processor in a one to one sort of way, but it is possible to think of them in that way. For example, you can get a scan code from the keyboard by reading port 0x60.
But increasingly there is a trend towards devices being memory mapped on the PC. The i/o APIC and HPET being examples. With a memory mapped device you program its registers ostensibly by writing to reserved addresses in main memory. The write never actually reaches main memory, however, but is instead diverted by hardware to the device in question.
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out 0x00, ax ; Just an example
in ax, 0x60 ; Just an example
It all depends upon the device in question. Some, like 0x60, can be read and written to, but others might be read only or write only. A port which reports whether some hardware device has successfully completed an operation might sensibly be read only, unless writing to that port accesses another of the device's internal registers.computertrick wrote:I did see something about the keyboard and 0x60 about 10 minutes ago. You can use the out instruction for outputting to hardware right? and input instruction
The keyboard generates a hardware interrupt when it has a scan code it wants you to read. Doing an "in al, 0x60" would then get you that scan code.I haven't tested the in ax, 0x60 instruction would that bring in data? I read up a few months back that keyboards don't send keystrokes instead the data they send needs to be put through an algorithm to calculate the correct keystroke? I suppose because of this receiving keyboard input you would also need to do this
Hi, thanks for your response I just triedCasm wrote:It all depends upon the device in question. Some, like 0x60, can be read and written to, but others might be read only or write only. A port which reports whether some hardware device has successfully completed an operation might sensibly be read only, unless writing to that port accesses another of the device's internal registers.computertrick wrote:I did see something about the keyboard and 0x60 about 10 minutes ago. You can use the out instruction for outputting to hardware right? and input instruction
The keyboard generates a hardware interrupt when it has a scan code it wants you to read. Doing an "in al, 0x60" would then get you that scan code.I haven't tested the in ax, 0x60 instruction would that bring in data? I read up a few months back that keyboards don't send keystrokes instead the data they send needs to be put through an algorithm to calculate the correct keystroke? I suppose because of this receiving keyboard input you would also need to do this
Scan codes tell you which key has been pressed, but they do not correspond to ascii or unicode characters. Therefore they have to be put through a look up table to obtain the correct character code. For one thing, some keys, such as the shift key, do not correspond to any character, and, for another thing, somebody typing on a Greek keyboard would get the same scan codes, but he wouldn't have much interest in seeing them translated into Latin characters.
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in 0x60, ax
http://webpages.charter.net/danrollins/ ... p/0057.HTMcomputertrick wrote:Hi, thanks for your response I just tried. I ran the operating system in qemu and checked the registers and AX is equal to 0x30fa when no key is pressed. Once a key is pressed this changes do you know any documentation to explain how to generate an ascii code with this information?. Also do you know of any documentation to explain these addresses more the 0x60 address how does the processor know that's the keyboard. If I take my computer apart will I see my keyboard connected to pin 96?Code: Select all
in 0x60, ax
That diagram is about thirty years out of date. Present day x86 processors are square in shape, and have around 200 pins sticking out of the bottom of them.I found a diagram of the processor
"in al, 0x60" is what he wanted. The al is on the "outside" when you are writing out to a port: "out 0x60, al".Levex wrote:I think"in 0x60, ax" is illegal/not what you wanted.
Sorry what do you mean keyboard event i accessed it directly right? Also what do you mean poll 0x60 until empty. Will the keyboard send b00000000 on empty ?. The program also assembled so it cant be a syntax problem. How come you have to poll until empty. And how would you poll until emptyLevex wrote:I was talking about if he wrote that in his binary it would either not assemble or dp undefined things which might be the reason why he received "scancodes" without a keyboard event.
OP, if you have written it the correct way, then the correct way is to clear the KB buffer on boot by polling 0x60 until it is empty. Then start receving kb IRQ, which is IRQ1 IIRC, and poll 0x60 when it has fired.
Cheers,
Levex.
Thank's for your reply I will empty the buffer. And yes I am using nasm and this code assembles fine.Levex wrote:I said that the keyboard encoder's buffer is mapped to I/O port 0x60, which you have been reading. It might contain undefined things and/or garbage. Better clear it. And yes it will return 0x00 when it has been emptied.
Polling means executing the instruction "in al, 0x60" continously until a condition is met. (In this case until $al == 0)
What assembler are you using? If you use NASM then it shouldn't assemble, because NASM uses the instruction dest, src syntax.
Cheers,
Levex.
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in al, 0x60