[CNLohr] has been tinkering with some fun parts of late. He’d found out that ordinary LCD screens could be used as simple touch sensors, and he had to try it for himself. He ended up building a little doohickey that combined USB C, an LCD display, and a touch interface, all for under a buck. You can check out the video below.
The key to this build was the CH32V003 CPU. It’s a RISC-V microcontroller that runs at a healthy 48 MHz, and it costs just 10 cents in reasonable quantities. A PCB etched to mate with a USB C cable eliminates the need for a connector.
[CNLohr] then gave the board a three-digit 7-segment LCD display from Aliexpress, which can be had for around 21 cents if you buy 100 or more. He then figured out how to drive the LCDs with a nifty trick that let the microcontroller use the display as a crude touch sensor. All in all, the total bill of materials for one of these things comes out somewhere under a dollar in quantity.
It’s mostly a random assemblage of tech glued together for a demo, but it’s a fun project. It’s worth checking out even if it’s just to learn how to create an integral USB C port on your own PCBs. The way it’s achieved with the etched contacts and milled-out tabs is pure elegance. Files are on Github for the curious.
We’ve featured a ton of [CNLohr’s] work over the years; the clear keytar was a glowing highlight, as were his early discoveries in the depths of the ESP8266.
It’s a cool idea, but that “USB connector” is not going to last more than a few mating cycles without hard gold plating, which would be more expensive than just using a USB socket.
The gold from the ENIG finish is so thin that it can be wiped off with a cloth. ENIG is to prevent the copper from oxidizing before the board is assembled, it’s not intended to be used as a card edge connector.
Fair point, but you just need to make a few with real ports, then the $1 units only need to work once for initial firmware loading.
He said he used enig which is hard gold plating made for edge connectors
ENIG is less than 100nm of pure gold. It’s very soft and rubs off easily. Hard gold is several µm of gold alloy. It’s much more durable and suitable for edge connectors and switch contacts.
Great video! I am impressed by the ingenuity. Also I think I can use the USB connector setup in some of my projects. Thanks a lot for sharing.
Keep in mind what the commenter above mentioned – the gold plating will disappear after a few cycles. Might be fine for initial firmware loading with a wireless MCU, but at that point I’d rather not bother with USB and make a pogopin jig.
Yes, it’s fun to learn the low-level details of how things work.
I get your excitement and enthusiasm!
I spent quite a few years doing the same.
You learn things that, if your brain works the “right” way, you can apply to diverse other topics and materials. If you understand what I mean, then you’re golden! 🤪
One thing people frequently forget is the way your brain works is not something set in stone. It will always improve in the direction you apply it.
Surely it is only a 555?
The CH32V003 MCU can also be programmed in Embeetle IDE: https://embeetle.com/#supported-hardware/wch/boards/ch32v003f4p6-evt-r0-1v1
And also check: https://embeetle.com/#blog/baremetal-ch32v003f4p6
Aww it looks like this isn’t ch32v003fun based
It cost considerably more than “a buck”. He had to choose non-standard options for the PCB manufacture which turned out very expensive.