Author Topic: The Living PCB Design Thread  (Read 227462 times)

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Offline stoic-lemon

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Re: The Living PCB Design Thread
« Reply #500 on: Mon, 06 February 2017, 07:03:08 »
Hi all. I've come up with this schematic after reading this thread and following a couple of tutorials. I'm just looking for some more experienced eyes to take a look at it and tell me if I've made any mistakes. I'm worried about the fact that I've used all the pins on the controller, and if my diodes are placed correctly, that kind of thing.




Offline skullydazed

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Re: The Living PCB Design Thread
« Reply #501 on: Mon, 06 February 2017, 09:55:17 »
You probably shouldn't connect the USB shield to GND, or if you do it should be through a cap and something like a 10M resistor. This is to avoid emitting unwanted RFI.

You've copied an extremely common pattern by putting all your decoupling caps off to the side, but as a general pattern I do not like to do this. It makes it difficult to determine where each one is intended to go. For example, what is C7's purpose? Instead I think it's better to have every passive component connected with a wire on the schematic, to make your intended placement/purpose obvious.

Otherwise looks like a great start!

Offline stoic-lemon

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Re: The Living PCB Design Thread
« Reply #502 on: Mon, 06 February 2017, 17:25:45 »
I really appreciate you taking a look and giving me feedback. I have nobody else to ask about this stuff lol. I'll take some time to digest what you said and make some changes. Thanks again.

Edit: After doing some research and learning a lot. I updated my schematic. I totally get what you mean about the previous one not being very good, especially for a novice like myself. When it comes to routing traces, I'll be glad I (attempted) to do it right so I understand a little better what is going on.

Altered the decoupling capacitors to show how they will connect. I'm really not sure this is right though.

It seems that the issue of the shield and hooking it to ground is a contentious one. I've followed what I think to be the safest advice, which matches what skullydazed said. Or at least I've tried to as it looks like I forgot to change the value of the resistor for the shield  :( .

« Last Edit: Wed, 08 February 2017, 21:33:54 by stoic-lemon »

Offline CthulhuMart

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Re: The Living PCB Design Thread
« Reply #503 on: Wed, 08 February 2017, 21:44:44 »
Can I get a sanity check on what I've got so far? It's a 40% form factor, ATMEGA32U4 chip, I'm a bit confused with the whole SMD stuff. I've used the SOD-523 footprint as they're smaller and hence give me more space to play around with for routing (I haven't started that yet.

Aside from that, is there anything glaringly wrong with what I've got?

Thanks!
CM.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #504 on: Sat, 11 February 2017, 00:50:48 »
For the shield to GND for the USB, what power rating resistors would I need in mW? Also, for the capacitor in the shield to GND for the USB, what VDC would I need? Are there any recommendations for those resistors and capacitors? They're 10KΩ 0603 resistors and 2.7F 0603 capacitor?
« Last Edit: Fri, 14 April 2017, 15:57:27 by HeroXLazer »

Offline bpiphany

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Re: The Living PCB Design Thread
« Reply #505 on: Sun, 12 February 2017, 05:57:20 »
For the USB shield there seem to be as many different recommendations as there are possible ways to combine resistor/capacitor/inductor networks or directly tie it to GND or floating. It's hard to tell what to use when/where/why.

Decoupling capacitors. Apparently that is a science of it's own with its fair share of hand wavering "rules". I found this thread with an interesting discussion. The answer by Connor Wolf at least makes a compelling argument that there is a difference between the different ways to hook them up. I'm pretty sure that at our low speed digital circuits the via placements are far from critical.

Offline replicaJunction

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Re: The Living PCB Design Thread
« Reply #506 on: Thu, 16 February 2017, 09:05:03 »
I apologize if this is a really stupid question, but I've been searching for a couple weeks and haven't found an answer. This is the biggest thing holding me back from a custom PCB design.

Is there a good KiCad footprint somewhere for a TRRS jack (and a corresponding part number to make sure I get the right one)?

Offline stoic-lemon

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Re: The Living PCB Design Thread
« Reply #507 on: Thu, 16 February 2017, 09:57:19 »
Not sure if this is 'the' one, but http://www.cui.com/product/resource/sj-4351x.pdf You could try your hand at making a footprint in KiCad.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #508 on: Thu, 16 February 2017, 17:07:50 »
I apologize if this is a really stupid question, but I've been searching for a couple weeks and haven't found an answer. This is the biggest thing holding me back from a custom PCB design.

Is there a good KiCad footprint somewhere for a TRRS jack (and a corresponding part number to make sure I get the right one)?
You may want to ask u/wootpatoot on Reddit, he made a PCB with a TRRS jack. He could probably give you a footprint.

Offline layornos

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Re: The Living PCB Design Thread
« Reply #509 on: Sat, 18 February 2017, 12:12:35 »
Dear all,

i want to use I2C as communication protocoll for a split keyboarrd.  As i understand, i need two 4,7k resistors like in this schematic:
160824-0

At the moment, the routing and schematic looks like this:
160826-1
160828-2

Regards

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #510 on: Sat, 18 February 2017, 23:09:59 »
Hey, if I want to use RGBW LEDs, how would I limit the power through USB 2.0? I am going to use 40 key switches and 40 RGBW LEDs.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #511 on: Sun, 19 February 2017, 15:04:39 »
Are there USB C 3.1 through hole KiCad footprints that work with something like this (http://www.digikey.com/product-detail/en/mill-max-manufacturing-corp/898-43-024-90-310000/ED1391CT-ND/5213140)?

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #512 on: Sun, 19 February 2017, 15:17:50 »
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #513 on: Sun, 19 February 2017, 16:24:38 »
Are there USB C 3.1 through hole KiCad footprints that work with something like this (http://www.digikey.com/product-detail/en/mill-max-manufacturing-corp/898-43-024-90-310000/ED1391CT-ND/5213140)?
Like this?
I already downloaded that, they're SMD, not through hole. Thank you anyway.

Offline Criterus

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Re: The Living PCB Design Thread
« Reply #514 on: Tue, 21 February 2017, 23:29:46 »
Does anyone current links for Kicad to the MX switch and the teensy 2.0 boards? I've downloaded a couple of libs and mods files most of them 2-3 years old and haven't had much luck making it from the Eeschema to PCBnew in Kicad. Its highly likely I'm doing something wrong, but I'd like to at least verify that I have the right/current parts installed to tinker on this software.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #515 on: Thu, 23 February 2017, 15:21:06 »
Does anyone current links for Kicad to the MX switch and the teensy 2.0 boards? I've downloaded a couple of libs and mods files most of them 2-3 years old and haven't had much luck making it from the Eeschema to PCBnew in Kicad. Its highly likely I'm doing something wrong, but I'd like to at least verify that I have the right/current parts installed to tinker on this software.
On Reddit, search up The Keebrary.

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #516 on: Sun, 26 February 2017, 10:30:05 »
I have a silly question but I rather be safe than sorry.
What's the correct wiring sequence?
MCU - Crystal - Capacitors or MCU - Capacitors - Crystal?
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline bpiphany

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Re: The Living PCB Design Thread
« Reply #517 on: Sun, 26 February 2017, 23:51:42 »
I have a silly question but I rather be safe than sorry.
What's the correct wiring sequence?
MCU - Crystal - Capacitors or MCU - Capacitors - Crystal?

I've seen both, and I don't think it matters too much. But it may be like with the bypass caps - there's a correct way to do it which will matter in extreme cases.. There's no reference design for the MCU in question?

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #518 on: Mon, 27 February 2017, 04:45:23 »
There's no reference design for the MCU in question?
The MCU is our earnest friend ATMega32u4, I have seen different approaches for this, even forking the trace from the MCU pins equally to crystal and capacitors, yet I'm unsure about the correct way to do it, if it even matters.
The datasheet doesn't seem to tell anything about this and I haven't found any CAD example.
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline pomk

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Re: The Living PCB Design Thread
« Reply #519 on: Mon, 27 February 2017, 05:33:31 »
Atmel has some application guides on this topic. http://ww1.microchip.com/downloads/en/AppNotes/Atmel-8128-Best-Practices-for-the-PCB-Layout-of-Oscillators_ApplicationNote_AVR186.pdf

The one pcb layout they actually show is not even symmetric, but does have caps before the crystal.

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #520 on: Mon, 27 February 2017, 05:39:52 »
Thanks pomk. Must have missed that pdf, and you've already posted it once, my bad forgetting it.

So you would personally put capacitors between MCU and crystal?
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline pomk

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Re: The Living PCB Design Thread
« Reply #521 on: Mon, 27 February 2017, 05:43:47 »
I usually follow the schematic, putting caps after the crystal. How the different sample pcb layouts have been crafted varies between chip manufacturers.

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #522 on: Mon, 27 February 2017, 06:22:59 »
I usually follow the schematic, putting caps after the crystal.
That was my same thought, although the design guides then states the following:
Quote
The load XTAL-IN capacitor should be placed first and closest to the XTAL-IN pin and ground
I guess I'll do this way and cross my fingers.

Again, thank you.
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline pomk

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Re: The Living PCB Design Thread
« Reply #523 on: Mon, 27 February 2017, 06:26:59 »
Any time

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #524 on: Mon, 27 February 2017, 17:15:28 »
So for an LED driver, does anyone have an image of an ATMEGA32U4 schematic with a IS31FL3731?

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #525 on: Wed, 15 March 2017, 18:15:32 »
What thickness of copper should I get for my PCB? Is there an advantage to get 3 ounces over 1 ounce?

Offline bpiphany

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Re: The Living PCB Design Thread
« Reply #526 on: Thu, 16 March 2017, 01:12:32 »
What thickness of copper should I get for my PCB? Is there an advantage to get 3 ounces over 1 ounce?

Not unless you need it to handle more current, which you don't on a keyboard (unless it doubles as a hig intensity light source or something..).

Offline ishtob

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Re: The Living PCB Design Thread
« Reply #527 on: Thu, 16 March 2017, 11:23:40 »
Hi all, its been a while since I posted on the make things forum. I recently started dabbling with type-c connectors for a build. decided that point to point soldering is not a very good idea in the long run as it is hard to reproduce consistent results and more prone to failure if I move this keyboard around a lot. This is what I came up with:



the idea is to use one of these as they look like they are built to outlast this century.



Question I bring here today is I am unsure of how to go about connecting the shield. Right now I have it tied directly to ground as this is what I have done with my hand wired build, it does not seem to have any issues and is working properly. Am I just lucky I am not getting any EMI or is this actually acceptable practice in type-C setups?

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #528 on: Thu, 16 March 2017, 11:29:01 »
Hi and welcome back,
I am unsure of how to go about connecting the shield.

For the USB shield there seem to be as many different recommendations as there are possible ways to combine resistor/capacitor/inductor networks or directly tie it to GND or floating. It's hard to tell what to use when/where/why.

Also, your EasyEDA link is broken, it points to their logo.
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline ishtob

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Re: The Living PCB Design Thread
« Reply #529 on: Thu, 16 March 2017, 11:34:51 »
Hi and welcome back,
I am unsure of how to go about connecting the shield.

For the USB shield there seem to be as many different recommendations as there are possible ways to combine resistor/capacitor/inductor networks or directly tie it to GND or floating. It's hard to tell what to use when/where/why.

Also, your EasyEDA link is broken, it points to their logo.


forgot to set it to public, try now

Offline ishtob

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Re: The Living PCB Design Thread
« Reply #530 on: Thu, 16 March 2017, 13:07:22 »
well, if anyone is adventurous enough and have a device with a type-c plug, let me know, I ordered a couple more since it costs the same. I will send you one of these with the USB port attached to test it out type-c to type-c

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #531 on: Tue, 04 April 2017, 21:33:40 »
Is this right?

Offline pomk

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Re: The Living PCB Design Thread
« Reply #532 on: Tue, 04 April 2017, 23:50:09 »
Depending on the uC it might. Difficult to say if it is not given.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #533 on: Wed, 05 April 2017, 08:41:27 »
ATMEGA32U4

Offline anson-IT

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Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #535 on: Thu, 06 April 2017, 18:37:08 »
Will this work for the ATMEGA32U4 instead of using Capacitors and a crystal. https://www.digikey.com/product-detail/en/murata-electronics-north-america/CSTCE16M0V13L99-R0/490-7851-1-ND/4380182
Also, does anyone know if the datasheet has the PCB footprint drawing flipped or flipped and rotated? Also, are  the pins shorted?

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #536 on: Thu, 06 April 2017, 19:38:34 »
Also, what fuses should I use for USB 2.0?

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #537 on: Fri, 07 April 2017, 05:25:53 »
Will this work for the ATMEGA32U4 instead of using Capacitors and a crystal.
You do need capacitors for either crystal and ceramic resonator. Read this from chapter 6.2 on.

Quote from: HeroXLazer
Also, what fuses should I use for USB 2.0?
Check the previous link at chapter 28.2. There's no fuse bits to set for USB (as far as I can read).
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #538 on: Fri, 07 April 2017, 08:36:57 »
What if I use a ceramic resonator with capacitors built in?

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #539 on: Fri, 07 April 2017, 08:50:30 »
What if I use a ceramic resonator with capacitors built in?
That could work, yet many prefer using crystals over ceramic resonators for the latter tend to be less precise. I'm not really an expert in that regard, so I just follow general recommendations.
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline pomk

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Re: The Living PCB Design Thread
« Reply #540 on: Mon, 10 April 2017, 07:49:28 »
Is this right?
I'm not sure if the pull-up on the reset pin is necessary, though even should it be so it won't break anything.
The caps next to the crystal seem a bit high valued, but of course they just have to match with the crystal itself.
You have a bit high total capacitance on the vbus, I believe that anything past 1 would not pass USB spec.
The USB shield should be connected to the keyboard chassis, while what you have in place will work I'm not sure of the purpose you have for those components.


Will this work for the ATMEGA32U4 instead of using Capacitors and a crystal. https://www.digikey.com/product-detail/en/murata-electronics-north-america/CSTCE16M0V13L99-R0/490-7851-1-ND/4380182
Also, does anyone know if the datasheet has the PCB footprint drawing flipped or flipped and rotated? Also, are  the pins shorted?
That might work, though it is difficult for me to see the point of it. Crystal and two caps will cost less and has been proven to work well with the C you have chosen.

Offline bpiphany

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Re: The Living PCB Design Thread
« Reply #541 on: Mon, 10 April 2017, 09:10:06 »
Resonators are supposedly not accurate/stable enough to support hi-speed USB. There's a built in resonator in the ATmega, if you want to use a resonator you may just use that.

I've always used 18pf caps for the crystal I use. Never analyzed the function further, but it seem to work. This completely depend on the crystal though. Atmel has some application sheet on crystal and caps.

I think a maximum of 10F is what USB allows without inrush limitation. You would probably get away with slightly more.

There's all kind of recommendations on how to connect the shield and GND. I'll stay out of that discussion...

Offline pomk

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Re: The Living PCB Design Thread
« Reply #542 on: Mon, 10 April 2017, 09:59:16 »
ah, my mistake there. Anything between 1 and 10 F should be fine.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #543 on: Mon, 10 April 2017, 16:58:48 »
So what about now?

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #544 on: Wed, 12 April 2017, 04:44:54 »
It looks fine, although that 22 Ohm resistor on the USB shield looks odd to me. I've seen recommendations to put a 4.7uF capacitor in parallel with 1 MOhm resistor but never a 22 Ohms.
Also, are you using PE2 as general I/O pin or as HWB? Because, for the latter, most people add a 1 KOhm resistor to it.
Lastly, out of curiosity, why are you adding a fuse on the VBUS rail?
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Offline HeroXLazer

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Re: The Living PCB Design Thread
« Reply #545 on: Wed, 12 April 2017, 08:35:37 »
I looked at other posts, and they all seemed to have 22Ω on the shield. HWB has a resistor on it. I have a fuse as circuit protection.

Online PancakeMSTR

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Re: The Living PCB Design Thread
« Reply #546 on: Thu, 13 April 2017, 16:22:58 »
I have a question: Can I use a surface mount Atmega32U4 in lieu of a Teensy 2.0 in a custom design I'm working on? Which Atmega should I use? Do I need to get anything else? Will it retain all the important functionality of the Teensy 2.0., e.g. compatibility with TMK or QMK (I don't know the difference between these) firmware?

For example, is this the same chip as is on the Teensy 2.0: https://www.digikey.com/product-detail/en/microchip-technology/ATMEGA32U4-AUR/ATMEGA32U4-AURCT-ND/3440960

Thanks.
   

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #547 on: Thu, 13 April 2017, 17:05:09 »
Can I use a surface mount Atmega32U4 in lieu of a Teensy 2.0 in a custom design I'm working on?
You can surely do, but the MCU alone won't suffice. You can read the whole thread (trust me, it won't take much) to see how other users accomplished that. Also, the datasheet is your friend.

Which Atmega should I use?
Either ATMega32u4 and AT90USB1286 (found on Teensy++ 2.0) are supported by TMK.

Do I need to get anything else?
A SPI programmer helps for most MCUs are blank and you need to flash the bootloader yourself. Some come already flashed but, the ones I found, they cost unreasonably more.

Will it retain all the important functionality of the Teensy 2.0., e.g. compatibility with TMK or QMK (I don't know the difference between these) firmware?
Not quite. You won't be able to use the TeensyLoader because the HalfKey bootloader is proprietary and not public. However, Grendel wrote a bootloader compatible with the TeensyLoader, you can ask him for the source.
Both TMK and QMK will work with the 32u4.

is this the same chip as is on the Teensy 2.0: https://www.digikey.com/product-detail/en/microchip-technology/ATMEGA32U4-AUR/ATMEGA32U4-AURCT-ND/3440960
Same chip, different form factor. The pins on the MU variant (the one found on the Teensy) are only exposed on the bottom side of the chip. The pins on the AU variant (the one you linked) are accessible from the sides which takes a bit more room but they are definitely easier to solder.
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.

Online PancakeMSTR

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Re: The Living PCB Design Thread
« Reply #548 on: Thu, 13 April 2017, 17:16:39 »
Can I use a surface mount Atmega32U4 in lieu of a Teensy 2.0 in a custom design I'm working on?
You can surely do, but the MCU alone won't suffice. You can read the whole thread (trust me, it won't take much) to see how other users accomplished that. Also, the datasheet is your friend




Right, I figured, but I'm having trouble understanding what else I need. There are a lot of surface mount components that I don't understand the purpose of on the Teensy. The basic idea here, I guess, is to replicate a (the necessary parts of) a Teensy on the PCB.

I am reading this thread, and researching stuff on my own, but I could definitely use direction, and would greatly appreciate it. I'm working on this on my own of course, but I'm nonetheless flailing about. I've never done this before.


So, supposing I use the surface mount atmega, I need to put a bootloader on it and program it. What software can I use to program it? Can I just use arduino software? How difficult is what I'm proposing here?


Is there a tutorial for designing a PCB with an integrated controller?
« Last Edit: Thu, 13 April 2017, 17:37:10 by PancakeMSTR »
   

Offline TalkingTree

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Re: The Living PCB Design Thread
« Reply #549 on: Thu, 13 April 2017, 17:42:18 »
I'm having trouble understanding what else I need. There are a lot of surface mount components that I don't understand the purpose of on the Teensy. The basic idea here, I guess, is to replicate a (the necessary parts of) a Teensy on the PCB.
Sure, replicating the Teensy is a good way to start. Its schematic will greatly help you in the process.

I am reading this thread, and researching stuff on my own, but I could definitely use direction, and would greatly appreciate it. I'm working on this on my own of course, but I'm nonetheless flailing about. I've never done this before.
Here are two ([1] [2]) ATMega32u4 breakout boards that you can examine to get an idea.

So, supposing I use the surface mount atmega, I need to put a bootloader on it and program it. What software can I use to program it?
avrdude to flash the bootloader, then, depending on the bootloader you choose, there's a number of different softwares for flashing firmwares, namely FLIP and dfu-programmer.
My opensource projects: GH80-3000, Skipad, TOAD (KotM Sept '17), TOAD v2 (KotM April '18), XMMX.