Show HN: F32 – An Extremely Small ESP32 Board
github.comAs part of a little research and also some fun I decided to try my hand at seeing how small of an ESP32 board I can make with functioning WiFi.
As part of a little research and also some fun I decided to try my hand at seeing how small of an ESP32 board I can make with functioning WiFi.
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.
These cables can be bought for like $200 mostly legally.
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!
Thank you! I agree, antenna definitely needs some improvement.
You should take the metal of the USB connector into account. This will significantly alter the emission pattern of the antenna. Try to find a radio amateur in your area, we have equipment to measure and software to predict antennas.
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!!
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/
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.
It only has 14 pins, 3 of which are 5v, 3.3v, and ground, so slight exaggeration :-) point taken though
These are nifty. I've used them in production, but if you want to make used of the charger it's difficult.
These are quite lovely. Ceramic SMD antennas are awesome.
Definitely would be more functional with more of the GPIOs exposed.
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.
I don't know, I see enough space for four GPIOs there. Not holes, obviously, but pads should be very workable.
It could be even smaller without that USB C port and have more GPIO pads.
Can anyone suggest a small module that supports 5 GHz WiFi?
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
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?
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.
Surface tension of solder in liquid state can hold the parts while upside down. Depends on weight of component & geometry of pads
"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.
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?
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.
JLCPCB also offers assembly and they're much, much cheaper, like an order of magnitude cheaper.
Wow thanks!!! I've been trying to find a cheap flex pcb supplier but the cheapest i found was $150 for 10. They are way cheaper making my project viable!
There's no makerspace nearby that could give you access to the tools and supplies to upgrade your skills?
This is great, well done! I don't know where I'd use this, but I'd definitely want to use it.
I was thinking "how much smaller than the cheap 30mm x 25mm boards on AliE can you go?" ... much smaller!
Very nice.
FYI XIAOs are 21x18mm.
I just learned about XIAO boards from Grok a few days ago, lol.
The Sense versions are pretty rad. Now I only have to add a battery and a touch sensor and I'm good to go.
Is it powerful enough to run a reverse proxy?
People that hide exploit devices in public chargers are going to love this one lol. Cheap, small and enough power
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.
> This can be seen in my highly necessary depiction below.
I love this. Fun and insightful article. Thank you.
Me too, but that particular picture was confusing. Shouldn't the board be with the human, 120 ft from the wifi access point being connected to? Now it looks as if the human screams at the board from 120 ft away, or something.
Other than that, hugely impressive project of course, it makes any board I've tried to design/assemble look impossibly huge. :)
No, I think the human holds a smartphone, is standing 38m away from the board, and is still able to connect to the distant board via the open Access Point it makes available. It's a testament to the communication between the Access Point and the human connecting to it.
FTA:
> In a clear line of sight test with the f32 placed about 3ft off the ground I was able to connect and perform scans/control the LED at roughly 120ft!
Fun fact, at that size the whole f32 is smaller than the wavelength of the radio waves it's using for 2.4GHz WiFi. Not that this is unique by any stretch, but it's still fun to think about. (Edit: formatting)
Thanks for checking it out!
01005? Oh no no no. I can barely do 0402s by hand and those are _2.5x_ larger.
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.
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.
Metric mm vs imperial thou. Confusing but at least explainable
Step 1: build a robotic arm with larger components...
With one of those mini-hotplates for reflow soldering and a LCD microscope it's still fairly doable.
infuriating fact: 0402 metric = 01005 imperial, 0402 imperial = 1005 metric. looks like this is the only semi-duplicate in common use.
And that's how I ended up with half a reel of 01005 resistors...
Wait wait wait what? 01005 isn't metric? They switched to imperial for just that size? What?
I was a bit outdated with resistor sizing and I don't have a great sources but apparently there are:
these sizes... and $1 is the one in your mind that shall not be written in inches. The "01005 imperial" is just 0402, so it's not going up to the metric 01005 scale or beyond. I think.Nice work, kudos!
> PCBWay does also offer assembly services
Seriously? For a tiny board like this also? Genuine question.
yes, but they use a machine, they don't do it by hand.
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