keyboard cover interface

[slothead]

This may be a dumb question, and I'm sorry if it is a waste of time or bandwidth for anyone, but here it is:
when I flop my keyboard cover onto the back of my SP3 it is disassociated from the SP3, that is, no depression of keys (while on the back) creates any inputs. what tells the SP3 that it is not being used!

By the way, I think the "off" function of the screen keyboard is counter-intuitive. I am always reaching for the keyboard-graphic button to turn it off rather than the big X button to do so. I think the keyboard-graphic button should toggle the keyboard screen on and off.

thanks for you time,
Tom

 

[leeshor]

Quite a few people have reported various issues folding the type cover back. We can only hope it's a driver/software issue. For now, don't do it.

 

[slothead]

Lee, I don't really have an issue. I'm just wondering what the interface is. Is it a bluetooth connection? And how does it know that I don't want to use it for input (while it is still attached)? Mine actually works great when it's folded behind the tablet, and I am so impressed I want to know how it does that!

I agree that the flex circuits between the keyboard and the SP3 connector could be a problem if flexed a lot, but then those things are designed as 'disposable' anyway. The only question in that regard is how long it will last before a new one is needed (but that is not really why I am posting today).

 

[jnjroach]

The Keyboard uses a USB and I2C Interface, the "spine" provides data and power....

 

[slothead]

You're headed in the right direction Jeff, but what I really wanted to know was how the keyboard knows that it is folded behind and to ignore keystrokes while being held in that configuration (sorry if I wasn't clear).

 

[jnjroach]

The Keyboard has an accelerometer that senses when the keyboard is folded back...

 

[slothead]

Ahh! Thanks. Interesting though, so it probably won't work in space... And if I am laying in bed or in some other odd position, there is a chance it won't work there either.

 

[buers]

Maybe, I don't understand accelerometer... Acceleration is of course also detectable in space. Just the acceleration by gravity you feel on earth is missing, typically.

OTOH, I can't see, how an accelerometer can reliably detect, how the cover is folded back. Some sort of sensor or switch, that really detects the bend of the cover looks more straightforward to me.

 

[slothead]

Don't feel bad, there are a lot of folks that don't understand the uses of accelerometers.

In cases like this, an accelerometer detects orientation because gravity is a force of acceleration - in the case of gravity 32.2 f/s^2. Of course there is very little gravity in space (we in the space industry call the gravity in low Earth orbit "micro-gravity").

But as you mention, acceleration IS detectable in space if you are acceleratiing, but you usually aren't. If you are in orbit you are not accelerating - so the accel says nothing (when it should be telling you in what direction the cover is oriented) or is intermittent - changing all the time. If you are accelerating, it depends on what orientation your cover is in - which could be anything. So by 'not working" I meant not working correctly.

And by the way I was only kidding - I've not seen any real test data on this accel application.

 

[buers]

If you detect the folding position by direction of the gravity force, wouldn't the type cover stop working up side down or in other strange positions (not folded back)? But it doesn't stop working here ...

 

[slothead]

If you detect the folding position by direction of the gravity force, wouldn't the type cover stop working up side down or in other strange positions (not folded back)? But it doesn't stop working here ...

That's a valid question - let me try it...
OK, this is what I found: With the cover hanging straight down from the SP it continues to work, but as soon as it passes the vertical (on the way to being folded back) the SP goes into 'autorotate' mode and the keyboard stops working (I was using the touchpad as a test input). I didn't want to hold up this post for a more extensive test, so I'll conclude that your supposition is correct (the keyboard does stop working), and that the keyboard is indeed controlled by an accel.

 

[buers]

Maybe, I misunderstand your post. To me it still doesn't look, like it was controlled by an accelerometer.

Your experiment: Change the angle between keyboard and screen. When > 180 degrees, keyboard stops working.

My experiment: Keep the angle between the screen and the keyboard at about 100 degrees. Rotate the SP3 (together with the keyboard) to arbitrary orientation in space. Keyboard works independent of orientation in space.

My conclusion (I am obviously not 100% sure): It is not controlled by an accelerometer (which could detect acceleration or orientation of the gravity force relatively to the keyboard), but rather by a sensor (or even a switch), which somehow can measure the angle between keyboard and screen. Two accelerometers could do the job as well.