Nov 19, 2025 at 3:09 PM EST

Show HN: F32 – An Extremely Small ESP32 Board

pegor

293 points

51 comments

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Nov 19, 2025 at 3:09 PM EST
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Nov 19, 2025 at 6:56 PM EST
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Step 02
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Discussion (51 comments)

Showing 35 comments of 51

tmpfs

4d ago

1 reply

This is a very cool experiment, even if the board doesn't end up being that practical (the antenna hack is going to be an ongoing issue I think) your documentation looks great at a glance!

pegor

4d ago

Thank you! I agree, antenna definitely needs some improvement.

anyg

4d ago

3 replies

If it is a little bigger to incorporate a bigger chip antenna and some GPIO pins, it is going to be very useful for a lot of IoT projects!!

pegor

3d ago

1 reply

Definitely would be more functional with more of the GPIOs exposed.

forsalebypwner

3d ago

If you want an ESP32 dev board with GPIOs exposed there are dozens (or hundreds, maybe thousands) of other options out there. It makes sense not to expose them when you're going for the smallest possible footprint.

margalabargala

3d ago

2 replies

The XIAO series of ESP32s is exactly that.

They are 4x the size though, almost exactly double in both length and width.

https://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/

dotancohen

3d ago

1 reply

It's also got 15 times as many GPIO pins as the board in the fine article.

And this PCBA will be smaller than the battery in most applications anyway.

margalabargala

3d ago

It only has 14 pins, 3 of which are 5v, 3.3v, and ground, so slight exaggeration :-) point taken though

sho_hn

3d ago

These are quite lovely. Ceramic SMD antennas are awesome.

PunchyHamster

3d ago

there is plenty of those already and not all too hard to make yourself, see LilyGo T01-C3

Its of format of original ESP8 so you get serial + 3 IO pins

NuclearPM

3d ago

1 reply

> This can be seen in my highly necessary depiction below.

I love this. Fun and insightful article. Thank you.

pegor

3d ago

Thanks for checking it out!

jacquesm

3d ago

1 reply

If you add another GPIO and make a silicone mold you could make an in-cable eavesdropper on USB connections that streams out the data via the wifi. That would be a pretty scary tool in the right circumstances.

atemerev

3d ago

These cables can be bought for like $200 mostly legally.

Gys

3d ago

1 reply

> PCBWay does also offer assembly services

Seriously? For a tiny board like this also? Genuine question.

kube-system

3d ago

yes, but they use a machine, they don't do it by hand.

puzzlingcaptcha

3d ago

4 replies

01005? Oh no no no. I can barely do 0402s by hand and those are _2.5x_ larger.

joemi

3d ago

1 reply

Wouldn't 0402 be 4x larger (if comparing lengths) or 16x larger (if comparing areas), not 2.5x?

Edit: Nevermind, I was wrong. I see now that the sizes don't actually directly correspond to the number codes! 01005 is 0.4mm x 0.2mm and 0402 is 1mm x 0.5mm. That's annoyingly confusing, IMO.

Neywiny

3d ago

Metric mm vs imperial thou. Confusing but at least explainable

numpad0

3d ago

1 reply

infuriating fact: 0402 metric = 01005 imperial, 0402 imperial = 1005 metric. looks like this is the only semi-duplicate in common use.

rts_cts

3d ago

And that's how I ended up with half a reel of 01005 resistors...

VTimofeenko

3d ago

FWIW, there's a step by step soldering guide in the readme:

https://github.com/PegorK/f32#building-the-f32

It looks doable, but of course a lot of carefulling is required when placing the components.

sho_hn

3d ago

With one of those mini-hotplates for reflow soldering and a LCD microscope it's still fairly doable.

Rebelgecko

3d ago

1 reply

Really cool. I just ran into a situation where it would be handy to have a small Bluetooth device that plugs into USB-C. However soldering something like this seems a bit beyond me, is there a more turnkey solution?

dotancohen

3d ago

1 reply

The company that printed the PCB, PCBWay, also offers PCBAs. They're really not expensive, though you might need to order in batches of multiples of five.

actinium226

3d ago

JLCPCB also offers assembly and they're much, much cheaper, like an order of magnitude cheaper.

Swannie

3d ago

1 reply

I was thinking "how much smaller than the cheap 30mm x 25mm boards on AliE can you go?" ... much smaller!

Very nice.

selcuka

3d ago

FYI XIAOs are 21x18mm.

actinium226

3d ago

3 replies

Neat! I just sent out an order to JLCPCB for an ESP32 based board. I don't have a rework station or any experience with SMT so I decided to go for their assembly options. It's 80 per board, but would probably be cheaper per board if I got more than 2 (I also have more components on my board than you).

Question about the instructions in your README, you say that once you're done with the top side, repeat for the bottom, but when you're working on the bottom side, what stops the elements on the top side from falling off once the heat passes through the board and melts the solder on that side?

brokenmachine

3d ago

"Bottom side must be done using a rework hot air gun, not possible with hotplate."

Basically you're hoping the bottom side doesn't get hot enough for everything to move or fall off.

pegor

3d ago

Working on the bottom side I only used the heat gun really carefully on the resistors then used a soldering iron with a fine tip for the usb-c connector since the leads are fairly large.

4b11b4

3d ago

Surface tension of solder in liquid state can hold the parts while upside down. Depends on weight of component & geometry of pads

stavros

3d ago

This is great, well done! I don't know where I'd use this, but I'd definitely want to use it.

allenrb

3d ago

Jesus. You had me at “hand-soldered 01005 components”.

I’m tempted to try a few of these just to see how disastrous my build efforts are.

ingen0s

3d ago

Nice work, kudos!

16 more comments available on Hacker News

View full discussion on Hacker News

ID: 45984461Type: storyLast synced: 11/22/2025, 10:17:03 AM

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Read the primary article or dive into the live Hacker News thread when you're ready.

Read Article View on HN

Nov 19, 2025 at 3:09 PM EST

Show HN: F32 – An Extremely Small ESP32 Board

pegor

293 points

51 comments

Mood

excited

Sentiment

positive

Discussion Activity

Very active discussion

First comment

Peak period

Day 2

Avg / period

17.5

Comment distribution35 data points

Loading chart...

Based on 35 loaded comments

Key moments

01Story posted
Nov 19, 2025 at 3:09 PM EST
4d ago
Step 01
02First comment
Nov 19, 2025 at 6:56 PM EST
4h after posting
Step 02
03Peak activity
21 comments in Day 2
Hottest window of the conversation
Step 03
04Latest activity
Nov 21, 2025 at 12:57 AM EST
3d ago
Step 04

Generating AI Summary...

Analyzing up to 500 comments to identify key contributors and discussion patterns

Discussion (51 comments)

Showing 35 comments of 51

tmpfs

4d ago

1 reply

This is a very cool experiment, even if the board doesn't end up being that practical (the antenna hack is going to be an ongoing issue I think) your documentation looks great at a glance!

pegor

4d ago

Thank you! I agree, antenna definitely needs some improvement.

anyg

4d ago

3 replies

If it is a little bigger to incorporate a bigger chip antenna and some GPIO pins, it is going to be very useful for a lot of IoT projects!!

pegor

3d ago

1 reply

Definitely would be more functional with more of the GPIOs exposed.

forsalebypwner

3d ago

margalabargala

3d ago

2 replies

The XIAO series of ESP32s is exactly that.

They are 4x the size though, almost exactly double in both length and width.

https://wiki.seeedstudio.com/XIAO_ESP32C3_Getting_Started/

dotancohen

3d ago

1 reply

It's also got 15 times as many GPIO pins as the board in the fine article.

And this PCBA will be smaller than the battery in most applications anyway.

margalabargala

3d ago

It only has 14 pins, 3 of which are 5v, 3.3v, and ground, so slight exaggeration :-) point taken though

sho_hn

3d ago

These are quite lovely. Ceramic SMD antennas are awesome.

PunchyHamster

3d ago

there is plenty of those already and not all too hard to make yourself, see LilyGo T01-C3

Its of format of original ESP8 so you get serial + 3 IO pins

NuclearPM

3d ago

1 reply

> This can be seen in my highly necessary depiction below.

I love this. Fun and insightful article. Thank you.

pegor

3d ago

Thanks for checking it out!

jacquesm

3d ago

1 reply

atemerev

3d ago

These cables can be bought for like $200 mostly legally.

Gys

3d ago

1 reply

> PCBWay does also offer assembly services

Seriously? For a tiny board like this also? Genuine question.

kube-system

3d ago

yes, but they use a machine, they don't do it by hand.

puzzlingcaptcha

3d ago

4 replies

01005? Oh no no no. I can barely do 0402s by hand and those are _2.5x_ larger.

joemi

3d ago

1 reply

Wouldn't 0402 be 4x larger (if comparing lengths) or 16x larger (if comparing areas), not 2.5x?

Edit: Nevermind, I was wrong. I see now that the sizes don't actually directly correspond to the number codes! 01005 is 0.4mm x 0.2mm and 0402 is 1mm x 0.5mm. That's annoyingly confusing, IMO.

Neywiny

3d ago

Metric mm vs imperial thou. Confusing but at least explainable

numpad0

3d ago

1 reply

infuriating fact: 0402 metric = 01005 imperial, 0402 imperial = 1005 metric. looks like this is the only semi-duplicate in common use.

rts_cts

3d ago

And that's how I ended up with half a reel of 01005 resistors...

VTimofeenko

3d ago

FWIW, there's a step by step soldering guide in the readme:

https://github.com/PegorK/f32#building-the-f32

It looks doable, but of course a lot of carefulling is required when placing the components.

sho_hn

3d ago

With one of those mini-hotplates for reflow soldering and a LCD microscope it's still fairly doable.

Rebelgecko

3d ago

1 reply

dotancohen

3d ago

1 reply

The company that printed the PCB, PCBWay, also offers PCBAs. They're really not expensive, though you might need to order in batches of multiples of five.

actinium226

3d ago

JLCPCB also offers assembly and they're much, much cheaper, like an order of magnitude cheaper.

Swannie

3d ago

1 reply

I was thinking "how much smaller than the cheap 30mm x 25mm boards on AliE can you go?" ... much smaller!

Very nice.

selcuka

3d ago

FYI XIAOs are 21x18mm.

actinium226

3d ago

3 replies

brokenmachine

3d ago

"Bottom side must be done using a rework hot air gun, not possible with hotplate."

Basically you're hoping the bottom side doesn't get hot enough for everything to move or fall off.

pegor

3d ago

Working on the bottom side I only used the heat gun really carefully on the resistors then used a soldering iron with a fine tip for the usb-c connector since the leads are fairly large.

4b11b4

3d ago

Surface tension of solder in liquid state can hold the parts while upside down. Depends on weight of component & geometry of pads

stavros

3d ago

This is great, well done! I don't know where I'd use this, but I'd definitely want to use it.

allenrb

3d ago

Jesus. You had me at “hand-soldered 01005 components”.

I’m tempted to try a few of these just to see how disastrous my build efforts are.

ingen0s

3d ago

Nice work, kudos!

16 more comments available on Hacker News

View full discussion on Hacker News

ID: 45984461Type: storyLast synced: 11/22/2025, 10:17:03 AM

Want the full context?

Jump to the original sources

Read the primary article or dive into the live Hacker News thread when you're ready.

Read Article View on HN