stanton@Polya.Stanford.EDU (Scott Stanton) (06/21/89)
Is it possible for an extended (101 key) keyboard to do chording on an AT (clone)? i.e. Can I detect if more than one key is being pressed at the same time? I have no qualms about going straight to the hardware interrupts on this one, assuming I can find any info on those. Which brings me to my next question: Could someone provide me with a description of how INT 9H works? Is it triggered by both key press and key release? How do I query the keyboard to determine which key(s) are currently being held down? I assume the info is available on some port, but I'm having trouble finding any books that will tell me anything about this. (or anything about ports at all, for that matter) --Scott (stanton@polya.stanford.edu)
dross@umn-d-ub.D.UMN.EDU (david ross) (06/21/89)
In article <10146@polya.Stanford.EDU> stanton@Polya.Stanford.EDU (Scott Stanton) writes: >Is it possible for an extended (101 key) keyboard to do chording on an >AT (clone)? i.e. Can I detect if more than one key is being pressed >at the same time? I have no qualms about going straight to the >hardware interrupts on this one, assuming I can find any info on >those. I know of at least one word processing program that detects keypress makes and breaks, and therefore lets you chord; I believe, however, they use port polling and not interrupts. Unfortunately, port polling will keep your program from working with many useful TSR utilities.
toma@tekgvs.LABS.TEK.COM (Tom Almy) (06/21/89)
In article <10146@polya.Stanford.EDU> stanton@Polya.Stanford.EDU (Scott Stanton) writes: >Is it possible for an extended (101 key) keyboard to do chording on an >AT (clone)? i.e. Can I detect if more than one key is being pressed >at the same time? I have no qualms about going straight to the >hardware interrupts on this one, assuming I can find any info on >those. Yes you can, and you don't need to take over the hardware interrupt (!). I had just such an application. I chained into interrupt 15H (system intercept) handling only the cases when AH=4FH (keycode function). In this case, AL has the key scan code (which has make/break encoded in the msb). If you return with carry clear, then the key is ignored. I would "snarf" the keycodes I was interested in into my own ring buffer, which my program would then empty. If you return with carry set, then the value in AL is used as the key code -- I made use of this in my oft-posted TSR KBDR.COM which makes the caps lock key behave as an additional control key. >Which brings me to my next question: Could someone provide me >with a description of how INT 9H works? You need to find a copy of the Technical reference manual, which unfortuately is now out of print. It also lists all the keycodes. >Is it triggered by both >key press and key release? Normally. It turns out the keyboard can be programmed to run in three different modes! >How do I query the keyboard to >determine which key(s) are currently being held down? You can't. I maintained a bit-per-key table to keep track of depressions. To make matters worse, the "typamatic" action causes multiple depress codes (without release codes) to be sent! My app required no repeating keys, so if I got a depress code when the table indicated already depressed, I ignored the code. Tom Almy toma@tekgvs.labs.tek.com Standard Disclaimers Apply
cjdb@tank.uchicago.edu (Charles Blair) (07/05/89)
In article <5404@tekgvs.LABS.TEK.COM> toma@tekgvs.LABS.TEK.COM (Tom Almy) writes: >[...] >You need to find a copy of the Technical reference manual, which unfortuately >is now out of print. It also lists all the keycodes. A more than decent substitute is the Technical Reference Manual that Hewlett-Packard puts out for its HP Vectra CS PC. Other clone-makers might have their own tech ref manuals which could do in a pinch as well. -- Bitnet: pmrcjdb@uchimvs1 Internet: cjdb@tank.uchicago.edu uucp: ...!uunet!mimsy!oddjob!tank!cjdb