Prototyping New Keyboard Designs (Using Plate Mounting and Direct Wiring)

[jdcarpe]

I really liked samwisekoi's idea for prototyping new keyboard designs by having a plate cut with the new layout, and bending the front and back of the plate to form the "base" of the keyboard. He then mounted all the switches in the plate and hardwired them into a matrix. Then connect the matrix to the pins of a Teensy 2.0 to control the keyboard. He calls this the "lowpoly" method, after the user who inspired him to try doing it this way (see this thread for more info). By using this method, we save the expense of having a custom one-off PCB designed and fabricated. Also, due to the bent edge design on the plate, a case is rendered unnecessary.

I am starting this thread as an offshoot of his GH60++ design thread, where we can post ideas for new keyboard designs and have them made into prototype boards. I have a few designs in mind already, in addition to samwisekoi's original 75% eRace/xRace/GH75/GH60++ design.

Input is welcomed! If you can help in any way, or if you need help with your design idea, post it here in this thread.

Link to samwisekoi's original design thread: http://geekhack.org/index.php?topic=38847.0

lowpoly's direct wiring technique: http://geekhack.org/index.php?topic=20898.0

[jdcarpe]

Reserved.

[jdcarpe]

Here are my first design ideas.

First, a 40% board:



Next, a design similar to the CM QuickFire TK:

This is shown with standard ANSI 125 layout, but it could have ISO and/or 150 layout.


Here is one inspired by the IBM Model F (84):



And finally, here is the crazy one. C64 repro:

The Enter/Return is 2.00-unit. F-keys on the side and other wide mods are all 1.50.
Could go with a 10-unit spacebar on this one.

[SmallFry]

So what is your end goal here?

[jdcarpe]

The goal would be to create new keyboards, like the GH60. If you have a crazy idea for a new keyboard, you can make a one-off without breaking the bank. Then try it out to see if it's a good design. Then show it to the world, and see if there is interest for production. You can test your crazy design, without having to design a new PCB, with the related expense that entails.

You'll see what I mean when I start posting my crazy design ideas.

[kmiller8]

You'll see what I mean when I start posting my crazy design ideas.

inb4 10x spacebar layout

[jdcarpe]

You'll see what I mean when I start posting my crazy design ideas.

inb4 10x spacebar layout

LOL

Also, because I can't design PCB's like this nice guy right here.

[SmallFry]

Ah, I see now. So what layouts are ye dreaming of now?
Edit: I can't haz read goodz.

[Matt3o]

post the source files! post the source files!

PS: does the KB feel different without a PCB?

[jdcarpe]

post the source files! post the source files!

PS: does the KB feel different without a PCB?

Source files posted.

I don't think it would feel any different without a PCB, unless the switches wobble in the plate holes.

[alaricljs]

The steel plates I've gotten my hands on hold fiercely onto the switches.  I think the only real thing you'll notice is the noise.  It'll be different.

[Matt3o]

the c64 is for Retro set, tell the truth

[jdcarpe]

the c64 is for Retro set, tell the truth

Yes it is exactly for the Retro set. I just wish now for a 2.00-unit Return, 1.50-unit Restore, and 1.50-unit F1, F3, F5, F7 (with front pad printed F2, F4, F6, F8).

I will paint the plate-case beige after I have it made.

[regack]

Sooo... can anyone make a plate that will work with this... I don't have plate skillz

[jdcarpe]

Here ya go...

[Lunartuna]

I've been thinking of what my ideal board layout would be....



No right shift, ctrl, alt, winkey.

[regack]

Here ya go...

Show Image

Wow, that was quick... now I just need to get the PCB prototype made :D

[Hubbert]

post the source files! post the source files!

PS: does the KB feel different without a PCB?

Source files posted.

Where?  Duh; I see the .DWGs.
1) Could you post as .DXF so I can open it directly in LibreCAD and FreeCAD?
2) Where could I find the GH60?
3) Better yet, does anyone have source for a standard 100% 104 key?

Thanks for this thread: it is very timely for me.  I would use breadboard(s), though: just solder to the leads, and wire to the breadboard(s), where the controller will be (get the header pins for $2 or whatever).  Put the matrix in a shoebox or baking pan or something.  Call it  "indirect direct wiring".

Would it be practical to use a rectangular slots for areas where you I'm unsure about the exact placement of individual keys?  I'm thinking of leaving parts of the bottom row as a slot, so I can slide keys around like beads on an abacus.

[alaricljs]

Slotted plates are only practical if you are using a properly drilled PCB and PCB mounted switches.

[Hubbert]

Slotted plates are only practical if you are using a properly drilled PCB and PCB mounted switches.

Thanks...I was referring to a very initial prototype, not the final version.  Electrically, the switches will be wired to the breadboard and then to the controller, so they don't care if Right Alt is in its 104-key position or in the 101-key Model M position.  Mechanically, the slot will constrain the switches to a given row, but they would be free to slide horizontally until I glued them down.

Once I determined the correct position, I would measure it, and make a plate with a square hole in the correct position.

Are you sure this wouldn't work?

EDIT: Thinking of Gutenberg, this would work best if we could have spacers, probably shaped roughly like a slice of bread (the "muffin top" would be above the plate, and a square section would dangle down into the slot), to fill in the empty spaces.

[alaricljs]

It'll work to some extent, but be sure to remember what's available in key cap sizes when you're playing that game.  There's going to be some wear on the switches that you slide around, and you won't be able to use stabilizers on any of the caps that need them.

For my bottom row idea I just used Sketchup and modeled out a few possible bottom rows.  I printed it and layed them 1 at a time just beneath my keyboard.  That way I could see where I use the space bar in comparison to different sized replacements.

You might be interested in a set of these things (1st and 2nd item on the page) from SP that can be positioned in the exact increments available for keycaps.  You can't type on it, but it might be good enough to decide on layouts.

[oneproduct]

Is there some way to take advantage of switches with built in diodes in terms of wiring? It seems like using built in diodes would be harder than what lowpoly did, where the diode was attached directly to the switch pin on one end and then its wire formed the main row wire.

[alaricljs]

"built-in" diodes aren't attached to the switch leads internally at all.  You have a bare switch around?  Check the bottom of it, the outer holes by the diode symbol are for the diode leads, the inner holes are for LED leads and of course you can only do one or the other.

[oneproduct]

Precisely what I was suggesting, and which confirms my thought. It seems that switches with built-in diodes would only make things harder than what lowpoly did, where he attached a diode to the switch pin directly. The only thing I could fathom is bending one of the diode legs upward and one of the switch pins downwards and seeing if they are long enough to touch (I'll have to look at this tomorrow). Then the other diode leg could attach to a row wire that runs along several switches.

[alaricljs]

Having seen lowpoly's work external diodes is how I would go

[TheSoulhunter]

Crossposting: http://geekhack.org/index.php?topic=40812.msg812308#msg812308

I'm working on a "ergonomic" gaming keypad atm, mainly for FPS (as RTS/MMO need sooo many buttons the "ergo" part becomes impossible). The idea is to place all the commonly used buttons so that they are comfortably to reach without stretching the fingers too far, forcing em into a awkward angle, or moving the hand around too much. Below is my first attempt for the layout, feel free to try it (print out) and see how good you can reach the center of the buttons (Note: For now the buttons are simply straight, but I will probably tilt/turn the keys later to match the angle of the fingers) and make suggestions for improvement etc...

Show Image

Someone willing to do a plate for this? ^^;

[simkev]

How about this? 45% board 

[jdcarpe]

Crossposting: http://geekhack.org/index.php?topic=40812.msg812308#msg812308

I'm working on a "ergonomic" gaming keypad atm, mainly for FPS (as RTS/MMO need sooo many buttons the "ergo" part becomes impossible). The idea is to place all the commonly used buttons so that they are comfortably to reach without stretching the fingers too far, forcing em into a awkward angle, or moving the hand around too much. Below is my first attempt for the layout, feel free to try it (print out) and see how good you can reach the center of the buttons (Note: For now the buttons are simply straight, but I will probably tilt/turn the keys later to match the angle of the fingers) and make suggestions for improvement etc...

Show Image

Someone willing to do a plate for this? ^^;

Beyond my plate skillz. :P

How about this? 45% board  :D (Attachment Link)

Here you go...

[TotalChaos]

@jdcarpe

Dude, u r so awesome!

I'm dying of hand pain and I need a ThumbShift keyboard like this:

This msg is about the simple version.

1. Exactly like a WASD or Filco or Rosewill except I need a short spacebar and 2 new 2x keys on each side of the spacebar.   These 2 new keys shall operate as thumbshift keys.  These keys would be aligned with the alt and spacebar.
+ Would fit into a cheap Rosewill case.
- Thumbshift keys might be better if they were placed at an angle.  But I simply don't know what the best angle is.


2. Exactly as above but with the missing F13-F24 keys above F1-F12.

3. As #1 but with angled thumbshift keys.

4. As #2 but with angled thumbshift keys.

For the angled shift key version, what would be the perfect length for the shift keys?  And why?

All I can say is that I can't handle pressing the thumbshift key directly next to ALT.  Using a 2x horizontal thumbshift key I can just barely use that by pressing on the far inner edge of the key, I think.  This is why I need to build a prototype.

How much will someone charge me to make a one-off  plate?  2-off?

What are the ramifications of using lubed switches on a keyboard that has no case?

I welcome any input on where/how the thumbshift keys should be placed?

If I build 2 at once does that shift the economics back in favor of the PCB method?  Or ?

I really love your bent-piece-of-steel idea as it just saved me massive amounts of stress and pain from worrying about how to do the case.  I just won't have a case.

[jdcarpe]

@jdcarpe

Dude, u r so awesome!

I'm dying of hand pain and I need a ThumbShift keyboard like this:

This msg is about the simple version.

1. Exactly like a WASD or Filco or Rosewill except I need a short spacebar and 2 new 2x keys on each side of the spacebar.   These 2 new keys shall operate as thumbshift keys.  These keys would be aligned with the alt and spacebar.
+ Would fit into a cheap Rosewill case.
- Thumbshift keys might be better if they were placed at an angle.  But I simply don't know what the best angle is.


2. Exactly as above but with the missing F13-F24 keys above F1-F12.

3. As #1 but with angled thumbshift keys.

4. As #2 but with angled thumbshift keys.

For the angled shift key version, what would be the perfect length for the shift keys?  And why?

All I can say is that I can't handle pressing the thumbshift key directly next to ALT.  Using a 2x horizontal thumbshift key I can just barely use that by pressing on the far inner edge of the key, I think.  This is why I need to build a prototype.

How much will someone charge me to make a one-off  plate?  2-off?

What are the ramifications of using lubed switches on a keyboard that has no case?

I welcome any input on where/how the thumbshift keys should be placed?

If I build 2 at once does that shift the economics back in favor of the PCB method?  Or ?

I really love your bent-piece-of-steel idea as it just saved me massive amounts of stress and pain from worrying about how to do the case.  I just won't have a case.

Do I understand correctly that for #1 you want a standard ANSI 104-style layout, but with 2x 2.00-unit thumb shift keys on either side of a 2.25-unit spacebar? What keys would you want where the shifts are now? For #3 & #4, would you want the thumb shift keys at a 45-degree angle?

A one-off plate in that size will probably be in the neighborhood or $30. To give you an idea of how much a one-off PCB would be, for the size of a 104-key keyboard PCB, you're easily looking at more than $200 for each in small quantities.

[regack]

A one-off plate in that size will probably be in the neighborhood or $30. To give you an idea of how much a one-off PCB would be, for the size of a 104-key keyboard PCB, you're easily looking at more than $200 for each in small quantities.

Now you've got me wondering if it could be cheaper to stitch together a couple of different smaller PCBs with headers...  the plate or case would hold everything together... sorry not trying to derail the thread with PCB talk

[jdcarpe]

Now you've got me wondering if it could be cheaper to stitch together a couple of different smaller PCBs with headers...  the plate or case would hold everything together... sorry not trying to derail the thread with PCB talk

I think it will still add up to the same. Or maybe more, due to the PCB setup costs. It's based on surface area, so I don't think you can get around the high cost that way.

@TotalChaos How does this work for you?

[TotalChaos]

@jdcarpe

Dude, u r so awesome!

I'm dying of hand pain and I need a ThumbShift keyboard like this:

This msg is about the simple version.

1. Exactly like a WASD or Filco or Rosewill except I need a short spacebar and 2 new 2x keys on each side of the spacebar.   These 2 new keys shall operate as thumbshift keys.  These keys would be aligned with the alt and spacebar.
+ Would fit into a cheap Rosewill case.
- Thumbshift keys might be better if they were placed at an angle.  But I simply don't know what the best angle is.


2. Exactly as above but with the missing F13-F24 keys above F1-F12.

3. As #1 but with angled thumbshift keys.

4. As #2 but with angled thumbshift keys.

For the angled shift key version, what would be the perfect length for the shift keys?  And why?

All I can say is that I can't handle pressing the thumbshift key directly next to ALT.  Using a 2x horizontal thumbshift key I can just barely use that by pressing on the far inner edge of the key, I think.  This is why I need to build a prototype.

How much will someone charge me to make a one-off  plate?  2-off?

What are the ramifications of using lubed switches on a keyboard that has no case?

I welcome any input on where/how the thumbshift keys should be placed?

If I build 2 at once does that shift the economics back in favor of the PCB method?  Or ?

I really love your bent-piece-of-steel idea as it just saved me massive amounts of stress and pain from worrying about how to do the case.  I just won't have a case.

Do I understand correctly that for #1 you want a standard ANSI 104-style layout, but with 2x 2.00-unit thumb shift keys on either side of a 2.25-unit spacebar?

Yes,  1 2.0 unit thumbshift key on each side of spacebar for 2 thumbshift keys total.
Unless u have knowledge of a better way?
Like if 2.25x keys are hard to get as flat or rounded-corner keys then that one could be a 2x key also.
I have not really researched the keycap problem yet.  I just know I don't want regular keycaps on the spacebar + thumbshift keys.  Those keys need "spacebar-style" keycaps so the edge of the key won't stab into my thumb.

What keys would you want where the shifts are now?

Regular shift keys

But if someone out there wants to chop the regular shift keys by removing 1.0x of space off of each shift key and then adding 2 normal keys in the empty space then I am agreeable to that proposal.  We could use the new keys as Fn keys, no problem.  If u could lay that out we could call it the Thumbshift-FN-key version.

The right shift key is soooo long that it can lose 1 unit of space off the right end, no problem.

The left shift is a 2.25 right?  So if we stole 1 unit from the left end then we get a 1.25 shift key... hmmm... That is not that big.  So I will say the Fn-key version should have a normal Left shift key for compatibility with regular ppl and a 1-unit shorter right shift key where the Fn key can go.  Eyeballing the Right shift key it looks like a 2.75 key.  So the Fn-key version shall have a Right Shift key that is 1.75 units long and a 1 unit Fn key taking up the right side space under the Enter key and over the Right CTRL key.

If someone out there has ergonomic information that says a 1.25 unit Fn key with a 1.5 unit right shift key is better then speak now or forever hold ur peace

Or if you have a better idea where the Fn key should be placed then let me know.  I don't use Fn keys much anyway.  Its mostly there for other ppl's benefit.

For #3 & #4, would you want the thumb shift keys at a 45-degree angle?

Sure   I'll build it like that.  If it sux then I throw it away and build a different one.

A one-off plate in that size will probably be in the neighborhood or $30. To give you an idea of how much a one-off PCB would be, for the size of a 104-key keyboard PCB, you're easily looking at more than $200 for each in small quantities.

So I am guessing a 2-off = $60.00 for steel and $210.00 for PCB?

I hafta build AT LEAST 2.  1 for me and 1 for whoever programs the keyboard controller.  I can't say that I will be healthy enuff to do the coding myself.  I don't want to fail in the middle of my project.  So to prevent myself from failing I will pay someone some $$ to code the controller and then I can maybe touch it up later or maybe add a fancy feature or something later on.

So anyway I need at least 2 to make a prototype and possibly 3.

[jdcarpe]

@TotalChaos

You have 8 plates in my GitHub at github.com/jdcarpe/TotalChaos

[TotalChaos]

@TotalChaos How does this work for you?

Show Image

AWESOME!  :cool:  You didn't cheap out on the design!  You have 5 extra holes for keyswitches above the cursor keys and underneath the Delete/End/PageDown keys!  You have achieved what no keyboard company on Earth seems able to do! :eek:

Thanks!  That means I can add 5 extra keys if I want!  I will probably use at least 3 of those keyslots!

Need a .dxf file or whatever filetype a steelcutter would want.

[jdcarpe]

AWESOME!    You didn't cheap out on the design!  You have 5 extra holes for keyswitches above the cursor keys and underneath the Delete/End/PageDown keys!  You have achieved what no keyboard company on Earth seems able to do!

Thanks!  That means I can add 5 extra keys if I want!  I will probably use at least 3 of those keyslots!

Need a .dxf file or whatever filetype a steelcutter would want.

You have .dwg files in the repository I linked above: github.com/jdcarpe/TotalChaos



P.S. You might want to have the drawing mirrored when they cut it, if you're having them laser cut. That way they just have to finish one side to remove burrs, and the underside will have the laser burn marks.

[TotalChaos]

@TotalChaos

You have 8 plates in my GitHub at github.com/jdcarpe/TotalChaos

You are ridiculously awesome!  .dwg files!  :DancingBanana:

I am thinking I can use a numpad 0 key (2.00 units of space) for my 2 different thumbshift keys and a LeftShift key (2.25 units of space) as my spacebar.

Since I am going to put padding on top of the keys anyway that should prevent any "sharp edge problems" for my thumb.

Also since you gave me FREE 5 extra slots for keys over the cursor keys I can hopefully safely ignore the Fn-Key versions and ppl can just install an Fn under the Delete key if they want an Fn key.  Right now I am thinking that makes more sense.  I don't think there is anything "wrong" with using a shorter right shift key its just that its easier to buy keycaps when u use as many "standard" sized keys as possible.

This is really blowing my mind.  So many keyboard companies have told me how hard or impossible it is to add keys to a keyboard and how important it is for them to chop important keys off.  To suddenly experience the opposite is a really wild feeling!

I now have a question for you:
The way you have made your plate in your CAD software, does it require a person to desolder switches in order to lube them?

Or is it like those special plates that allow opening and lubing the switches while they are soldered to the plate?

I don't understand what the actual difference between the 2 types of plates is.  I don't understand what the different advantages and disadvantages is.  I just know that it sounds more user friendly to put switches on plates that allow to open the switch and lube or change the spring without having to go thru the horrendous hassle of desoldering everything and resoldering everything.

What are your views on easymod plates vs. hostilemod plates?

[jdcarpe]

@TotalChaos

You have 8 plates in my GitHub at github.com/jdcarpe/TotalChaos

You are ridiculously awesome!  .dwg files!  :DancingBanana:

I am thinking I can use a numpad 0 key (2.00 units of space) for my 2 different thumbshift keys and a LeftShift key (2.25 units of space) as my spacebar.

Since I am going to put padding on top of the keys anyway that should prevent any "sharp edge problems" for my thumb.

Also since you gave me FREE 5 extra slots for keys over the cursor keys I can hopefully safely ignore the Fn-Key versions and ppl can just install an Fn under the Delete key if they want an Fn key.  Right now I am thinking that makes more sense.  I don't think there is anything "wrong" with using a shorter right shift key its just that its easier to buy keycaps when u use as many "standard" sized keys as possible.

This is really blowing my mind.  So many keyboard companies have told me how hard or impossible it is to add keys to a keyboard and how important it is for them to chop important keys off.  To suddenly experience the opposite is a really wild feeling!

I now have a question for you:
The way you have made your plate in your CAD software, does it require a person to desolder switches in order to lube them?

Or is it like those special plates that allow opening and lubing the switches while they are soldered to the plate?

I don't understand what the actual difference between the 2 types of plates is.  I don't understand what the different advantages and disadvantages is.  I just know that it sounds more user friendly to put switches on plates that allow to open the switch and lube or change the spring without having to go thru the horrendous hassle of desoldering everything and resoldering everything.

What are your views on easymod plates vs. hostilemod plates?

They have the "easymod" switch openings. The difference is between the holes is the difference between a square and the image below. Where the red arrows are is where the release tabs are able to open on the switch housing, so that you can remove the top of the housing without desoldering.




I like to use the easy open switch holes, so I can mod or lube the switches, if I want. I honestly don't find myself opening the switches very often once they are installed on the plate, but it's nice to know I could if I wanted. The square holes might be a tad more stable holding the switch in place, but they don't move much, if at all. Once the switches are soldered to a PCB, they definitely won't move around.

[CaptainAsshat]

Out of curiosity how loose would a switch be if it weren't soldered to a pcb but just mounted in a plate?

[dorkvader]

Out of curiosity how loose would a switch be if it weren't soldered to a pcb but just mounted in a plate?

I only have a few plates to have tested with (vintage WYSE, rosewill, biniaris phantom, kmac) but the plates hold switches pretty well for me, especially for stainless steel.

This is, bytheway, the most awesome topic ever. JDcarpe: what program are you using? Kicad? I'm seriously considering making a sweet layout one-off to use at work I'm thinking 40% (ish) with a tenkey to the side, and some macros, but I want to learn how to make the dwg files myself.

Also, can anyone recommend a steelcutter? I'd also want someone to bend the sides down to make a sort-of case.

[TotalChaos]

@JDCarpe

What is the story with the bending of the steel?

Are there instructions in the .dwg file for the SteelCutter like "Fold on the dotted line" or somesuch?

Is it easy for steelcutters to bend steel in a precise manner?

Thanx!

[jdcarpe]

This is, bytheway, the most awesome topic ever. JDcarpe: what program are you using? Kicad? I'm seriously considering making a sweet layout one-off to use at work I'm thinking 40% (ish) with a tenkey to the side, and some macros, but I want to learn how to make the dwg files myself.

Also, can anyone recommend a steelcutter? I'd also want someone to bend the sides down to make a sort-of case.

Thanks! I have designed a "40XL" with a sort of tenkey on the side. I'll find it and post it here. I use QCAD by RibbonSoft. It's fairly inexpensive, and seems to be full featured for 2D drawing. I've been sending my plate designs to The_Beast to be laser cut. His guy does a really excellent job. And The_Beast says that his guy recently acquired a metal bending machine, so we're going to see if he can bend the plates to form the "legs." We haven't tested it, yet.

@JDCarpe

What is the story with the bending of the steel?

Are there instructions in the .dwg file for the SteelCutter like "Fold on the dotted line" or somesuch?

Is it easy for steelcutters to bend steel in a precise manner?

Thanx!

There aren't instructions, but if you look at the drawing, you'll see "notches" cut where it should be pretty obvious you want it bent. Not really sure about the whole bending process, since I haven't tested it, yet. samwisekoi had a plate bent by a sheet metal place local to him, after receiving the laser cut plate.

[jdcarpe]

@dorkvader, here is the link to the "40XL" drawing file: https://github.com/jdcarpe/Plates/blob/master/New/40XL.dwg
Maybe you can modify that to suit your design idea.

[Matt3o]

I'm after this



and this

[Grimey]

Having done a couple of keyboard using this method, I think this is a great idea all around.

The only thing I have a reservation on is the plate being both the plate and the "base".  I am totally with the plate bending at the sides to created at least a small platform, but I think having mounting points at either the back/front or left/right sides of the plate would be a better solution all around.  Making a couple of wood blocks to mount the custom plate onto would be trivial for anyone with a hand saw and provide a lot more custom configuration options.  This could of course be done in tandem with the plate folding on the top/bottom and mounting points on the left/right, or something like that.  Also having a place to mount the teensy would be a pro.

The other problem is swapping caps on a board with a hand wired matrix like this.  I have only handwired ALPS boards, but when you pull a cap on a keyboard that doesn't have a PCB you are likely to pull the switch up with it.  The wiring does not have enough holding power to keep the switch in place and allow the user to pull the cap off, which can have a small downside of breaking the matrix wiring. 

Otherwise bring on the custom plate options.  I think a lot of cool designs can be done this way on the cheap.

[nebo]

@dorkvader, here is the link to the "40XL" drawing file: https://github.com/jdcarpe/Plates/blob/master/New/40XL.dwg
Maybe you can modify that to suit your design idea.

Show Image

Show Image

Oh God I need this, but with a num row.

[jdcarpe]

I'm after this

Show Image

and this

Show Image

Do you know what the dimensions are for the stabilizers on the 5-unit spacebar?

[jdcarpe]

Oh God I need this, but with a num row.

Why do you need a num row when you have a num pad?

[nebo]

Oh God I need this, but with a num row.

Why do you need a num row when you have a num pad?

1) I have other ideas for those keys.
2) Starcraft would be hell.
3) !@#$%^&*()

[jdcarpe]

Oh God I need this, but with a num row.

Why do you need a num row when you have a num pad?

1) I have other ideas for those keys.
2) Starcraft would be hell.
3) !@#$%^&*()

Would you want a 2-unit backspace, or split backspace? Number row extend over the number pad?