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First PCB - General Questions and Schematic check

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Torch09:
Hello everyone,

After I had always used complete boards for my small projects, I wanted to build my own.
This is my first board; I would like to ask some questions which I’m not really sure of and maybe you could look over the circuit to point out if there are errors I made.
My plan is to design it with EasyEDA and use the production and assembly service from JLCPCB.

The Microcontroller I’m using is a RP2040, because I’ve worked with the Raspi Devices before, and the documentation seems pretty good for beginners (mostly the Hardware Design Guide).

There are some components which I changed, because JLCPCB has “Basic Parts” which don’t cost more in the assembly process, for every part which is not a “Basic Part” I need to pay 3€ setup fee.
I will only get 5 Boards, which I won’t sell, so this would be getting expensive for this basic test board.

I have added my schematic and the BOM to the attachments.
The BOM includes the ws2812b and the header, but I’ll solder them myself. JLCPCB doesn’t support two side assembly, so no other chance :D .

I’m currently working on making the PCB, if everything from the schematic looks good, I will add it to the post.
Currently the RP2040 is not available on JLCPCB so I thought about replacing it with a STM32F030C8T6 but currently I hope that it gets restocked in the near future.

Function:
The board should just be a basic test board where I can test some code and with some lighting on the bottom.
I’ve added some GPIOs to a Header for future connection to buttons or something along the lines.

Questions:
USB Protection:
I’ve added a ProTek SRV05-4 TVS. I haven’t found circuits with this specific IC to verify my schematic, so I connected it like the Datasheet said. The Schottky on the 5V line is a MDD SS14.
Would the USB protection for 5V and Data work this way or is this done another way? I’ve read about littlefuses, but they are sadly not in the JLCPCB Basic Part list.

Crystal:
I had to use another Crystal, because the one in the Raspi Guide isn’t supported for Assembly. The Crystal I choose is a X322512MSB4SI (12MHz like the one used by raspi). This Crystal has 4 pins of which two are GND, I connected it the same way Raspi does but had to calculate the Capacitors (Crystal CL: 20pf, Cstray=5pf). I used the formular form adafruits blog: “C1, C2 = 2*CL – 2*Cstray”

Schematic:
Is there something which you would add or remove from the schematic to make it more readable or to comply with any rules? I tried to mimic the schematic design from people who seem to know what they are doing ( :D ).

General:
Would you make something another way or is there anything which would make sense to include in the schematic / design?


Datasheets for quick navigation:
TVS:
https://datasheet.lcsc.com/lcsc/1809192313_ProTek-Devices-SRV05-4-P-T7_C85364.pdf

Crystal X322512MSB4SI:
https://datasheet.lcsc.com/lcsc/2103291203_Yangxing-Tech-X322512MSB4SI_C9002.pdf

RP2040 Hardware Design guide:
https://datasheets.raspberrypi.com/rp2040/hardware-design-with-rp2040.pdf

W25Q128JVSIQ Flash SPI:
https://datasheet.lcsc.com/lcsc/1811142111_Winbond-Elec-W25Q128JVSIQ_C97521.pdf

AO3400A MOSFET for 3.3 to 5v:
https://datasheet.lcsc.com/lcsc/1811081213_Alpha-&-Omega-Semicon-AO3400A_C20917.pdf


Thanks in advance for your help!

Benta:
Why is the schematic split into x number of single sheets? It's impossible to read without spending 20 times as much time as with a regular schematic.
You have no space problems on the sheet. Placing each component on a separate sheet is senseless.
I have no other comments, as the design is undecipherable.

Torch09:
First of all, thanks for the comment.

The PDF consists of 2 A4 sheets, do you mean to make the sheet bigger (A3+) so the logical blocks fit on one "big page" and not two small ones?
I read on Autodesk tips topic to use a standard sheet of paper, which is A4. Is this something like best practice but not used in the real world?

Everything on one page like this?:
https://github.com/ShawnHymel/rpi-pico-debugger-shoe/blob/master/hardware/rpi-pico-debugger-shoe/rpi-pico-debugger-shoe_schematic.pdf

 

Benta:

--- Quote from: Torch09 on January 19, 2022, 09:10:26 pm ---The PDF consists of 2 A4 sheets, do you mean to make the sheet bigger (A3+) so the logical blocks fit on one "big page" and not two small ones?
I read on Autodesk tips topic to use a standard sheet of paper, which is A4. Is this something like best practice but not used in the real world?

Everything on one page like this?:
https://github.com/ShawnHymel/rpi-pico-debugger-shoe/blob/master/hardware/rpi-pico-debugger-shoe/rpi-pico-debugger-shoe_schematic.pdf

--- End quote ---

No.
I mean putting all relevant components on one sheet and using wires to connect the pins.
Placing certain parts, like the power supply, or connectors on a separate sheet can make sense, but needs careful thinking.
But your "little boxes, little boxes, made of..." renders it unreadable.
Instead of just following a wire, I'm forced to look for labels all over the place, and I'm not even sure if there's a 1:1 correspondence or if I have to look further.
I attach an example of a readable schematic.

Torch09:
ok, understood that.
Just followed the example from the sheet I linked, but I will make my sheet more readable and update the attachment.

Thanks.

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