Numpad keyboard project - suggestions

[Keyboard_Warrior364]

Hello everyone, here I'd like to post some pictures of schematics and pcb for my numpad project. I would be grateful for your suggestions of what could be done better, or if i made any obvious mistakes.
I made a separate pcb for the usb connector. The two pcbs are supposed to be connected with this cable: MX-92315-0410.

[Keyboard_Warrior364]

Here is the numpad in question

[Keyboard_Warrior364]

Just realized that i posted an older schematic version with the wrong values of capacitors. Should be 100nF and 4.7uF.

[gipetto]

you should remove all the matrix diodes and dedicate one pin per switch, and one for the backlight.

[Findecanor]

Doesn't the ATmega32u4 have a grounding pad at the bottom of the package? I'm not sure if it's advisable to have vias under it.

[Applet]

My suggestions:

• Add ICSP header if you want to change bootloader or if device is bricked (check out tagconnect if you do not want or have space for a connector)
• ESD-protection diodes for USB-traces
• Route USB-data traces differentially (xSignals is very convenient i Altium and good enough)
• You could do a constant current source for the LEDs with a lm317 or such, then you do not have to change resistor depending on LED
• Personally I'd do this with the ATmega32U2, you can fit both QFN and the LQFP footprint in about the same size as the QFN ATmega32U4
• The lines in silkscreen for showing direction on the diodes if very thin, I'd increase thickness
• What's with the + and - and lines on the silkscreen on bottom? (they are also very small/thin)

[Keyboard_Warrior364]

Thank you so much for the suggestions.

I've checked my package of the atmega32u4, it doesn't have a a ground pad at the bottom.

The thickness of the lines for diodes is 12mils, I'll change them to 15mils.
And will try to implement your other suggestions, especially the data lines.

I'm also making a 60% board as well and will have to make the same changes to it, luckily I haven't routed everything yet
I'll post an update of both.

Here is the current unfinished pcb.

[Applet]

I'd suggest rotating all the switches 180 degrees on the 60%. GMK/Cherry keycaps can hit the switch if using that rotation. Same issue on the numpad. Not sure about best rotation for the vertical stabilized keys, someone else here probably knows (I don't think it matters)

[Keyboard_Warrior364]

That regarding switches is very good to know, thanks. Though I am still torn on what to do, I did orient them this way since the LEDs would be positioned on the top. As far as I've seen most keycaps that support backlight have the legends on the upper side

[gipetto]

if you're going to have backlight the leds should be at the top of the switch. i think it's better to have separate boards for backlit and non backlit as compromising doesn't work. the led traces turn the pcb into a rats nest so there's no advantage having them at the bottom where they are unusable.

[Keyboard_Warrior364]

 gipetto you are definetelly right that it turns the board into a rats nest. When i made the first prototypes, I made two boards, one with LEDs and one without. Firstly I wanted to see if the barebones keyboard pcb works and then if the one with LEDs worked. Luckily both versions worked. Then I started doing changes to the shape of the board and routing, so that it would fit into the case that i plan on making. I thought it would be wise to ask for additional advice here seeing as there are a lot of people making their own projects.

Some of the problems I'm having is finding bright smd LEDs that are also low current, was looking at some that are 5mA. Wanted white ones, since they give a neutral look, but the ones I used on the prototype might not be bright enough.
I did find green, yellow and red ones that should be very bright though.

And thanks for taking the time to help.

[Findecanor]

I'd suggest rotating all the switches 180 degrees on the 60%. GMK/Cherry keycaps can hit the switch if using that rotation.

I have found that problem only with EnjoyPBT's dished F and J caps, or with silencing clips (which require GMK/Cherry and the LED window south).

Not sure about best rotation for the vertical stabilized keys, someone else here probably knows (I don't think it matters)

For Numpad-+ and Numpad-Enter keycaps, it does not matter for clearance ...
On backlit keyboards, the LED is either left or north. I think north is more common.

[Keyboard_Warrior364]

Applet, you mentioned the ICSP header for changing the bootlaoder or if the board gets bricked.
What would be the advantage of changing the bootloader from the one already on the MCU?
Or if somebody else knows, I'd be grateful for the answer.

[Applet]

Applet, you mentioned the ICSP header for changing the bootlaoder or if the board gets bricked.
What would be the advantage of changing the bootloader from the one already on the MCU?
Or if somebody else knows, I'd be grateful for the answer.

You get a few more functions with the QMK bootloader, like being able to exit bootloader from matrix scan(button press), flashing indicator sound etc, nothing major. I have no personal experience with the QMK bootloader, I've only been using stock, so someone else should be able to give some more input.

[Keyboard_Warrior364]

Hello again, its been a while since I've last posted something.
Here is a quick update:
            1. As you guys have advised, I've added an ICSP header.  (modded the footprint for tag connect so it could also support a smd 6 pin connector)
            2. Routed the data tracks for the usb differentially with an impedance of 90 Ohms.
            3. Added USBLC6-2SC6 for ESD protection.

I did the same thing for both the numpad and the 60% pcb.

Will post my schematics as well later.

[Keyboard_Warrior364]

Here are a few pics.

Edit: Forgot to say thank you for all your help.

[Keyboard_Warrior364]

So its been a while since I've posted anything, so i thought I'd share how the first prototype looks. Its still a bit rough, but we'll make the next version better, once we make proper tooling.

Sorry for the poor image quality.

What do you guys think so far?

[felix71]

fantastic wowwww... Do you have the electronic schematic? thank you

[simplycanada]

I don't know if you were looking to sell these but anyhow these below are just my own comment if I was to look at one..

I appreciate the use of an usb header as to be able to use my own connector&location

and nice to have the extra row of keys on top to optionally use too (especially when some non-numpad keyboards sometimes are lacking a few keys toward the right side)

the only one thing I maybe voluntarily would had liked to see was that the pcb allowed 1u sized plus key on it as this seem quite lacking in other numpads