Can we design the teensy alternative for keyboards?

[pomk]

that sparkfun trinket should work just fine.

[vvp]

Conversion from 3.3V output to 5V input:

• Check the specification for input levels on your 5V device. They often accept anything above 3.0 V as logical HIGH. If so then you do not need any conversion from your 3.3 CMOS output to your 5V device input if the connection is short and the fan-out is low.
• If the 5V device needs more than 3.0 V to recognize input HIGH then you need a level converter. The most simple one is just a pull up in series with a FET to ground. If you need more output power then a dual-FET (NFET+PFET) is an option or just use a specializes part just for this.

For conversion from 5V output to 3.3V input a simple resistor voltage divider will often do. Or a pull-up in series with a FET or a dual-FET or you can use something specialized just for this.

There are also full 8-bit wide 3.3V - 5V bidirectional level shifters. E.g. 74LVX4245MTC.
And of course bidirectional 1-bit level shifters. E.g. TXB0101DBVR.
Just search for level shifters. You will find hundreds of them.

What exactly you can use depends on impedance and maximum rise/fall times.

Edit: Actually the dual FET option will not be that easy. The P-FET would need to be properly biased and that can be hard to find. This is a problem for a level converter but not for a simple "amplifier".

[matt3o]

I would be more interested in looking for thumb/pointing sticks analog or digital that we could use for the purpose. I've found a couple that simply act as an switch-per-direction.

[pomk]

Cleaned this up and changed the font to something more explicit in regard to 1 vs I. Also corrected two typos.

PINOUT.jpg (344.43 KiB) Viewed 5722 times

edit:
and new button footprint for bootloader plus a bit more rigid USB 'peninsula'. I decided to keep the old footprint for the reset button, as the larger pads are easier to work with if one wants to do stuff with them.

prod_maybe.jpg (341.71 KiB) Viewed 5701 times

[Sythe]

On the USB connector feet through holes, I think you will want to increase the pad size on the top side of the board to pick up enough solder during SMT.

I have an Atmel board at work I was going to show as an example, but forgot to take a photo of it. Will try and remember Monday.

[vvp]

I've found a couple that simply act as an switch-per-direction.

I'm not sure switch per direction is useful. The keyboards already have many keys/switches. One can just assign some of them in some layer to work as mouse keys (switch for a direction).

[matt3o]

I'm not sure switch per direction is useful. The keyboards already have many keys/switches. One can just assign some of them in some layer to work as mouse keys (switch for a direction).

I agree, the difference would be that you can place it between a couple of keys and use it as a joystick

[pomk]

On the USB connector feet through holes, I think you will want to increase the pad size on the top side of the board to pick up enough solder during SMT.

I have an Atmel board at work I was going to show as an example, but forgot to take a photo of it. Will try and remember Monday.

I can enlarge the front holes, the inner ones are a bit cramped for space

(edit: they are exactly according to molex spec though)

[Sythe]

Yeh saw that. That might work well enough. I'll try get the photo of the board on Monday to show you what they did.
I work with SMT assembly in my job and showed your board layout to the design engineer at work who does our PCB design and he also didn't think there would be enough surface area for solder paste application during SMT. For hand solder, this obviously isn't an issue.

[pomk]

Well it's good to have professional opinions on these things from time to time
I'll try to adjust the design accordingly where possible.

[Sythe]

Image quality is absolute arse as my phone's camera wouldn't focus.
But you can see how they did it, they increased the pad size on the outside of each hole(same footprint top and bottom) but SMD is only top side, so all solder it picked up from top side pads.
Even on these boards, we have seen a couple that didn't have a heap of solder on them and the bottom side looked quite bare with very little solder touching the through hole feet on the connector.

[pomk]

I can do a similar thing with the outermost holes.

[pomk]

So last communal check before I generate the gerbers again for matt3o.

I modified the USB pads as suggested:

traces.png (73.02 KiB) Viewed 5590 times

I added the pin descriptions on the top side for all pins that have some special considerations.

top-silk.png (56.03 KiB) Viewed 5590 times

Lastly I rotated the corner pads by 45 degrees and adjusted the outline to match. With this change the board should no longer be as pointy in your fingers as it was before.

outline.png (54.03 KiB) Viewed 5590 times

[tentator]

Wow!!

[Sythe]

Looks great.
I would suggest you look at doing the panelising yourself, so its done right.
Especially since you have pads all the way around the edge you want to be safe.

For panelising, look at doing it with breakaway tabs.
I think something like larger tabs around usb and clear section opposite side and small tabs near corners should work.

[pomk]

I have no experience in panelization, so I think it would be ill advised for me to begin practicing with this project. The first prototypes had no cosmetic problems from the panelization applied by the company who built them.

[matt3o]

I asked a new quote for the new board... unfortunately the new button has to be sourced externally and the new design basically costs the same as the old one with two buttons... yeah I know... now looking for alternatives.

[pomk]

Oh...

Just tell me if we need a further revision. If you can get the supplier of the manufacturer, who could not get panasonic, I could try to look for another alternative from their catalog.

[HeroXLazer]

Hey, if I want to design a PCB like this with the ATMEGA32U4, what capacitors/resistors/etc., do I need? I also want to use a USB-A port, so how would the schematic look like compared to a normal keyboard PCB using an ATMEGA32U4?

[matt3o]

Oh...

Just tell me if we need a further revision. If you can get the supplier of the manufacturer, who could not get panasonic, I could try to look for another alternative from their catalog.

the problem is the usb port and the button. I'm trying to find alternative manufacturers. Thanks for you help I'll let you know if we need further updates in the coming hours

[pomk]

I have used pcbway in my own projects (though not pcba) and they don't charge for the option of us sending in the components ourselves. They have instructions on how to order from mouser/digikey etc. so that the components end. Up at their door. Their pricing seems fair as well. They do have a turnkey option as well, but I'm not familiar with the component pricing which would ensue.

Just a thought.

[matt3o]

I'm talking with pcbway right now, but it seems both the usb port and the buttons are not very common and hard to find (making them pretty expensive anyway)

[pomk]

At least unless we supply the components to them ourselves, I guess?

edit: arrow seems to have both the button and the USB connector in stock.

[matt3o]

shipping and import tax add up to the final cost, we would need to find a supplier that has all the components and see if we can really save something

[pomk]

Arrow stocks all of the components and has no shipping charges for orders over 50 USD.

I guess the import tax would be calculated according to the PCBA services country? For china that would be 17% I imagine.

[matt3o]

Arrow stocks all of the components and has no shipping charges for orders over 50 USD.

I guess the import tax would be calculated according to the PCBA services country? For china that would be 17% I imagine.

would you be able to send me a complete order with all the components from arrow?

[pomk]

With just the components (for how many boards?) or also with the overrun specified by pcbway?

[Sythe]

Here is a list to compare to that I did up a couple of weeks ago. Prices could be a little different now(but in general can be used a price guide).
These are the quantities I would be buying for a 200pc run being put together for me locally(Aus).
If you are looking at pcbway, do costing based on their wastage requirements as that is what would need to be bought for the production.

https://docs.google.com/spreadsheets/d/ ... edit#gid=0
(A quick way to search for price comparison is findchips.com)

If you were going to source parts yourself for production done in China, I think your options are either buy in China or get someone to move it in from HK, sending direct from outside of China can destroy any savings you were going to have.

[matt3o]

thanks Sythe, that's perfect. I believe the only thing to change is the switch, your total is far from the quote I got. They basically quoted almost double of that.

[Sythe]

Oh yeah, this was done before the button change. Forgot to update, but still gives a reasonable price guide.