5 ms·

How a devboard works (and how to make your own)

96 points by kaipereira 11mo ago

eqvinox 11mo ago
Honestly my problem is that all my designs turn into devboards since I always have a kind of "FOMO" of not breaking something out and then needing it later to bodge things... and then I'm left with a crowded board where I don't even use two thirds of things...
- MrGilbert 11mo ago
  I‘m sure you've already considered that, but what about iterating your design, e.g. redesigning the board if you need more outputs?
- sweetjuly 11mo ago
  Test pads are great for these anxious breakouts. I usually drop tons and tons of test pads on the back of my boards as it's a very dense and unobtrusive way to expose traces that you probably don't need.
hackingonempty 11mo ago
This is a really excellent tutorial, thank you for making it.
jmole 11mo ago
I thought this article would first start with the most essential question: "How to decide what you need on your devboard". Without that critical piece of design work, you may as well call this "How to build a Raspberry Pi Nano from scratch". Which, to be fair, is also a good article to write. But step 1 for really building a dev board is answering the question, "What do I need from this that I can't get from a $5 Amazon purchase?"
- brailsafe 11mo ago
  > What do I need from this that I can't get from a $5 Amazon purchase? A month of enjoyment tinkering on a hobby just for the hell of it.
- madaxe_again 11mo ago
  I just go the other way - dev boards are so cheap you can just take a scalpel to them and take off the bits you don’t want.
neuvarius 11mo ago
Crosspost to r/embedded if you haven’t. See you there.
exmadscientist 11mo ago
I don't like this tutorial. It purports to teach you "what everything on the PCB fundamentally does, and what every single component on your PCB is actually for!" but it gets the reasoning for a lot of stuff wrong, sometimes badly wrong. I think every single instance of a component with a numerical value picks the value with a misleading or even completely wrong justification. Even if the tutorial gets to an OK schematic in the end, it shouldn't be teaching shoddy reasoning. (And the author doesn't seem to understand decoupling capacitors, but most people don't understand decoupling capacitors, including most datasheet authors, so that doesn't surprise me.) Also, KiCad's "solutions" for BOMs are hilariously, absurdly terrible. But that helps me earn a living, so I can't complain too much....
- randmeerkat 11mo ago
  Do you have a tutorial that you like?
  - exmadscientist 11mo ago
    I agree with the sibling comment that "How to decide what you need on your devboard" is the tutorial that would be nice to see. This article is trying to do too many things at once (design a dev board, baby's first schematic, baby's first PCB, baby's first JLCPCB order,...) and that's really the only one that's novel. The rest of it is standard EE stuff that's covered in a lot of places (with varying degrees of success). As for decoupling, I've written about how to do it in various places scattered across the internet. I should really collect it all in one place one of these days.
- althaine 11mo ago
  Can you clarify the issues with KiCad's BOM flow?
  - exmadscientist 11mo ago
    What BOM flow? It doesn't bloody well have any! At no point in the entire design process within KiCad does this design ever get part numbers assigned for its resistors or capacitors (to pick one thing). That's not acceptable for professional work. A Bill of Materials ABSOLUTELY MUST DESCRIBE THE MATERIALS used in the assembly of the PCBA. Internal part numbers are perfectly acceptable: assigning a generic RES-0402-10k or WIDGETCO-PN987654321 or whatever would be OK by me. KiCAD does not really do this, as evidenced by how this design reaches "design complete" without being... complete. EVERYTHING MUST HAVE AN ORDERABLE PART NUMBER OR INTERNAL PART NUMBER. But the resistors are the easy parts. SMD thick film resistors are basically all interchangeable. Things like the ceramic capacitors (MLCCs) cannot be substituted for each other because they all bloody well behave differently so good luck getting the same behavior if you randomly pick a capacitor vendor on LCSC each time you build boards! That's how EEs get fired, and deserve it. When I generate a build package in Altium, it has complete lists of every part in the design, its MPN, at least one supplier to purchase it, and the SPN for that MPN. (Sometimes internal parts don't have suppliers assigned, but then they're tracked elsewhere in the project or company organization.) There are also assigned alternates in many cases, though they are typically inadequate. Larger projects should use entirely internal part numbering, but that's a real headwind for smaller stuff. All of this comes from a single master part database, plus a project part database, and never gets touched by hand after a library entry's birth. KiCad is so crap at doing this that last month a client literally paid me thousands of dollars to fix up a garbage KiCad design package that didn't have this information properly stored. There are several add-ins for KiCad that claim to do BOMs better... but it's not standard, so if you don't document what you did and how (which you do not have to do in real CAD software, because it is built in and the CAD vendor documentation plus the years of built-up lore will cover you!) it may as well not exist. Certainly it didn't exist in any sort of usable form for this project.
barishnamazov 11mo ago
Not sure if it was due to higher load from HN or my IP location, but your website is inaccessible to me right now: "This deployment is temporarily paused."
- LaFolle 11mo ago
  For me also it is unreachable "This deployment is temporarily paused"
- h1fra 11mo ago
  If I had to guess, it's because it's loading a bajillion images that are not compressed
matt3210 11mo ago
Dang, I wanna read this but the site seems down
- Tharre 11mo ago
  https://web.archive.org/web/20251107235749/https://kaipereira.com/journal/build-a-devboard https://web.archive.org/web/20251107235749/https://kaipereir...
  - bartvk 11mo ago
    That now yields a "429 Too Many Requests" I didn't know HN could bury a site like that. Edit: I had to turn off my VPN and now it works.
wayvey 11mo ago
While the deployment is down you can read it on web.archive.org https://web.archive.org/web/20251107235749/https://kaipereira.com/journal/build-a-devboard https://web.archive.org/web/20251107235749/https://kaipereir...
moi2388 11mo ago
“ This is how are schematic will look when done the tutorial” Well, that bodes well for the rest of the article..
avipars 11mo ago
This deployment is temporarily paused Any archived version?
- St_Alfonzo 11mo ago
  https://web.archive.org/web/20251108052512/https://kaipereira.com/journal/build-a-devboard https://web.archive.org/web/20251108052512/https://kaipereir...
massifist 11mo ago
I found this article very informative. Thanks for writing it.
kaipereira 11mo ago
Hey guys, thanks for all the love :D The website went down because of the traffic and large images, so I've temporarily switched hosting, and it should stay up now (DNS propagation might take a bit though), but I'm going to get those images smaller ASAP, thanks to everyone who posted web archives! I'm also going to alter some of the reasoning for some of the stuff like decoupling capacitors, but the guide is still meant for complete beginners, and lots of the terminology/reasoning can be pretty overwhelming, and I still have a lot to learn about decoupling/other stuff! I'll also add a part about what you actually need on your devboard, that's a great suggestion! You can find a JOURNAL.md in EVERY SINGLE one of my hardware projects https://github.com/KaiPereira?tab=repositories https://github.com/KaiPereira?tab=repositories so if you guys want to see more guides/tutorials, let me know :D

96 points by kaipereira 11mo ago

Honestly my problem is that all my designs turn into devboards since I always have a kind of "FOMO" of not breaking something out and then needing it later to bodge things... and then I'm left with a crowded board where I don't even use two thirds of things...

MrGilbert 11mo ago
I‘m sure you've already considered that, but what about iterating your design, e.g. redesigning the board if you need more outputs?
sweetjuly 11mo ago
Test pads are great for these anxious breakouts. I usually drop tons and tons of test pads on the back of my boards as it's a very dense and unobtrusive way to expose traces that you probably don't need.

hackingonempty 11mo ago

This is a really excellent tutorial, thank you for making it.

jmole 11mo ago

I thought this article would first start with the most essential question: "How to decide what you need on your devboard". Without that critical piece of design work, you may as well call this "How to build a Raspberry Pi Nano from scratch". Which, to be fair, is also a good article to write. But step 1 for really building a dev board is answering the question, "What do I need from this that I can't get from a $5 Amazon purchase?"

brailsafe 11mo ago
> What do I need from this that I can't get from a $5 Amazon purchase? A month of enjoyment tinkering on a hobby just for the hell of it.
madaxe_again 11mo ago
I just go the other way - dev boards are so cheap you can just take a scalpel to them and take off the bits you don’t want.

neuvarius 11mo ago

Crosspost to r/embedded if you haven’t. See you there.

exmadscientist 11mo ago

I don't like this tutorial. It purports to teach you "what everything on the PCB fundamentally does, and what every single component on your PCB is actually for!" but it gets the reasoning for a lot of stuff wrong, sometimes badly wrong. I think every single instance of a component with a numerical value picks the value with a misleading or even completely wrong justification. Even if the tutorial gets to an OK schematic in the end, it shouldn't be teaching shoddy reasoning. (And the author doesn't seem to understand decoupling capacitors, but most people don't understand decoupling capacitors, including most datasheet authors, so that doesn't surprise me.) Also, KiCad's "solutions" for BOMs are hilariously, absurdly terrible. But that helps me earn a living, so I can't complain too much....

randmeerkat 11mo ago
Do you have a tutorial that you like?
- exmadscientist 11mo ago
  I agree with the sibling comment that "How to decide what you need on your devboard" is the tutorial that would be nice to see. This article is trying to do too many things at once (design a dev board, baby's first schematic, baby's first PCB, baby's first JLCPCB order,...) and that's really the only one that's novel. The rest of it is standard EE stuff that's covered in a lot of places (with varying degrees of success). As for decoupling, I've written about how to do it in various places scattered across the internet. I should really collect it all in one place one of these days.
althaine 11mo ago
Can you clarify the issues with KiCad's BOM flow?
- exmadscientist 11mo ago
  What BOM flow? It doesn't bloody well have any! At no point in the entire design process within KiCad does this design ever get part numbers assigned for its resistors or capacitors (to pick one thing). That's not acceptable for professional work. A Bill of Materials ABSOLUTELY MUST DESCRIBE THE MATERIALS used in the assembly of the PCBA. Internal part numbers are perfectly acceptable: assigning a generic RES-0402-10k or WIDGETCO-PN987654321 or whatever would be OK by me. KiCAD does not really do this, as evidenced by how this design reaches "design complete" without being... complete. EVERYTHING MUST HAVE AN ORDERABLE PART NUMBER OR INTERNAL PART NUMBER. But the resistors are the easy parts. SMD thick film resistors are basically all interchangeable. Things like the ceramic capacitors (MLCCs) cannot be substituted for each other because they all bloody well behave differently so good luck getting the same behavior if you randomly pick a capacitor vendor on LCSC each time you build boards! That's how EEs get fired, and deserve it. When I generate a build package in Altium, it has complete lists of every part in the design, its MPN, at least one supplier to purchase it, and the SPN for that MPN. (Sometimes internal parts don't have suppliers assigned, but then they're tracked elsewhere in the project or company organization.) There are also assigned alternates in many cases, though they are typically inadequate. Larger projects should use entirely internal part numbering, but that's a real headwind for smaller stuff. All of this comes from a single master part database, plus a project part database, and never gets touched by hand after a library entry's birth. KiCad is so crap at doing this that last month a client literally paid me thousands of dollars to fix up a garbage KiCad design package that didn't have this information properly stored. There are several add-ins for KiCad that claim to do BOMs better... but it's not standard, so if you don't document what you did and how (which you do not have to do in real CAD software, because it is built in and the CAD vendor documentation plus the years of built-up lore will cover you!) it may as well not exist. Certainly it didn't exist in any sort of usable form for this project.

barishnamazov 11mo ago

Not sure if it was due to higher load from HN or my IP location, but your website is inaccessible to me right now: "This deployment is temporarily paused."

LaFolle 11mo ago
For me also it is unreachable "This deployment is temporarily paused"
h1fra 11mo ago
If I had to guess, it's because it's loading a bajillion images that are not compressed

matt3210 11mo ago

Dang, I wanna read this but the site seems down

Tharre 11mo ago
https://web.archive.org/web/20251107235749/https://kaipereira.com/journal/build-a-devboard https://web.archive.org/web/20251107235749/https://kaipereir...
- bartvk 11mo ago
  That now yields a "429 Too Many Requests" I didn't know HN could bury a site like that. Edit: I had to turn off my VPN and now it works.

wayvey 11mo ago

While the deployment is down you can read it on web.archive.org https://web.archive.org/web/20251107235749/https://kaipereira.com/journal/build-a-devboard https://web.archive.org/web/20251107235749/https://kaipereir...

moi2388 11mo ago

“ This is how are schematic will look when done the tutorial” Well, that bodes well for the rest of the article..

avipars 11mo ago

This deployment is temporarily paused Any archived version?

St_Alfonzo 11mo ago
https://web.archive.org/web/20251108052512/https://kaipereira.com/journal/build-a-devboard https://web.archive.org/web/20251108052512/https://kaipereir...

massifist 11mo ago

I found this article very informative. Thanks for writing it.

kaipereira 11mo ago

Hey guys, thanks for all the love :D The website went down because of the traffic and large images, so I've temporarily switched hosting, and it should stay up now (DNS propagation might take a bit though), but I'm going to get those images smaller ASAP, thanks to everyone who posted web archives! I'm also going to alter some of the reasoning for some of the stuff like decoupling capacitors, but the guide is still meant for complete beginners, and lots of the terminology/reasoning can be pretty overwhelming, and I still have a lot to learn about decoupling/other stuff! I'll also add a part about what you actually need on your devboard, that's a great suggestion! You can find a JOURNAL.md in EVERY SINGLE one of my hardware projects https://github.com/KaiPereira?tab=repositories https://github.com/KaiPereira?tab=repositories so if you guys want to see more guides/tutorials, let me know :D