First, I found that many of you computer types look down upon us WebTv users. I can understand as I was a radio amateur when the FCC took away our 2 meter band & gave it to CBers who need not even be tested.
But, I’d like to know how the infer-red(sp?) keyboard that I am typing on from my recliner 12 ft the “black box” atop my TV works. It has 97 keys, 47 of which are upper & lower case. Does it have 144 differant IR codes none of which has any effect on my 2 VCR’s nor my TV? It appears that a lot of thought went into the keyboard alone, not to mention the rest of the system. Microsoft now owns WebTv, but, I heard that they were not the original developers. Anybody know the Straight Dope?
Carl- Don’t know about the keyboard, but I do know it’s ‘infrared’.
Every little bit counts.
Thanks for the spelling lesson! Do I have to stay after class?
You could always assume that the keyboard only uses two pulses ( one for 0 and one for 1) and transmits the ASCII or UNICODE value of the character pressed.
I would agree with Headless Cow’s answer, with the exception that it might use special guard signals, to mark the start of a character pulse, or something.
But, it definately would transfer the data digitally instead of having a code for each character.
Likely it uses scan codes, which are just keyboard-ascii, basically. Numbers which represent the keys, but with codes for non-printable characters (F# keys, arrows, etc) and based on layout, where the number pad keys have a different code than the number row keys.
Or, if it’s a special WebTV keyboard which isn’t just a modified standard IR keyboard, they might have made up their own scan codes based on the specific wiring scheme used.
(Keyboards don’t use a horizontal/vertical grid, because any two keys in a row or column would mess this up. Instead they use a different layout. No idea what it is, or how exactly it works, but my keyboard is capable of registering any two keys, most three key combos, and some (but not a lot) of four key combos. For instance, alt-shift-up arrow-left arrow doesn’t work, but alt-shift-up arrow-right arrow does. It’s not directly related to the physical layout from what I can tell…)
I would suspect though that the keyboard is a fairly standard model with branding, instead of their own design.
There are some standards for wireless device operation, and I’m not sure if WebTV uses them or has a proprietary solution, but in any case there is usually some common concepts to everybody’s solution. What WhiteNight posted was on the mark. Here’s some more detail.
IR keyboards typically have a protocol stack partly implemented in hardware and partly in software. At the hardware level you have raw bit encoding on the IR link (usually asynchronous, IIRC), so as mentioned above, it’s digital data. The hardware usually also handles some simple framing features such as beginning and end of frame markers, busy-link detection (in case another wireless device is transmitting), and perhaps CRC codes.
Above that there are some software layers that handle things like detection of lost or erroneous data, flow control, retransmission of bad packets, sometimes segmentation/reassembly, and connection/disconnection, all of course underneath the OS keyboard (or whichever) API. Conceptually, it’s basically just a packet protocol, and the contents of the packet are device specific - in this case, keyboard and mouse events encoded into the packet data field. This lets a bunch of wireless devices potentially coexist peacefully and be independently addressed. As with TCP/IP, you can chose not to use certain capabilities if your device doesn’t need them.
The wireless communication standards also have a zillion and a half higher level features that are probably not used by keyboards, but are available to other devices - stuff like session management and object transfer. These might be used, say, by a PDA, or some such device with wireless capability and more smarts than a keyboard. But at some level it’s all the same protocol. Cool, huh?
peas on earth
As a card carrying techno geek, I want you to know that I don’t look down on you for using WebTV. Anyone with confidence in their own skills and knowledge doesn’t feel the need to pick on other people.
My 72 year old aunt got WebTV because it is easier for her to use then a PC (she can sit on the couch and use it with the TV). She loves it, e-mails me daily, and even bought a digital camera to send me pictures. She is smart as a whip, and could have learned computers in no time. She simply made the best choice for her.
You Go Carl!
PS, I think the keyboards work by magic.
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