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.
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!
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.
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.
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.
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.
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.
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.
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.
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 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.
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
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.
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.
01005? Oh no no no. I can barely do 0402s by hand and those are _2.5x_ larger.
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
With one of those mini-hotplates for reflow soldering and a LCD microscope it's still fairly doable.
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.
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...
> This can be seen in my highly necessary depiction below.
I love this. Fun and insightful article. Thank you.
Thanks for checking it out!