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Original: Programmer’s Stories (id: iProgrammer)
Passionate Embedded Programmer
George Hilliard is an embedded developer who enjoys tinkering in his spare time. Recently, he has been experimenting with cheap processors that support Linux, the cheaper the better.
He had a sudden idea: could he create a simple computer in the form of a business card?
Although he has seen other engineers create personalized electronic business cards with various interesting functions, including simulating USB flash drives, flashlights, and even wireless transceivers.
But he had never seen a business card that runs Linux, so he thought he would make one himself.
Well, he actually made it, and here is the finished product. This is a complete, minimal ARM computer that runs a custom Linux firmware built with Buildroot.
(Front of the business card)
(Back)
Features of the Linux Business Card Microcomputer
> There is a USB interface on the corner, which starts up about 6 seconds after plugging it into a computer, displaying as a USB flash drive and a virtual serial port, allowing login as the root user from the built-in shell.
> 8MB of flash storage contains his resume and photos. The shell also has some classic games (e.g., 2048) and a MicroPython interpreter.
> The bootloader size is 256 KB, the kernel is 1.6 MB, and the entire root filesystem is 2.4 MB;
> There is also a writable directory. The remaining space on the flash is enough for others to put some stuff.
Design and Assembly
George detailed the process of making the business card in a separate article:
www.thirtythreeforty.net/posts/2019/12/designing-my-linux-business-card/
Cost List
The material cost of this Linux microcomputer was kept very low by George, totaling $2.88, which is about 20 RMB.
Of course, there are some unquantifiable costs that are not included, such as his time.
He filtered through many processors and finally chose the F1C100s (which includes both CPU and RAM), purchased from a certain treasure. Other components were sourced from LCSC.
Related Resources
1. Source Code
> The Buildroot source code is available on GitHub:
https://github.com/thirtythreeforty/businesscard-linux
> Supports Linux version 5.2 and above
https://github.com/thirtythreeforty/linux/tree/f1c100s-v5.2.4
> U-Boot source code:
https://github.com/thirtythreeforty/u-boot/tree/f1c100s-v2019.04
2. F1C100s Documentation
> Datasheet:
www.thirtythreeforty.net/media/F1C100s_Datasheet_V1.0.pdf
> Reference Manual:
www.thirtythreeforty.net/media/Allwinner_F1C600_User_Manual_V1.0.pdf
3. Circuit Diagram of George’s Business Card
www.thirtythreeforty.net/posts/2019/12/my-business-card-runs-linux/businesscard.pdf
As a business card, having a USB port is already quite minimal. Other I/O, network ports, etc., are all discarded. Otherwise, wouldn’t a Raspberry Pi be more appealing?
Netizen Comments
George’s business card sparked heated discussions on Hacker News.
@sagargandecha:I think this is amazing.I generally don’t often hand out physical business cards.So, if I do give one out, it will be to someone I think would find it interesting.For anyone security-conscious, they can grab it from GitHub and check the code.For others, all the necessary information is reflected on the card, even without functional design, it is still very attractive.No matter what your goal is, whether it’s finding a job or discussing business, the production cost of this card is easily justified.
@nilsb:While this is a fascinating project, I would have some security concerns about plugging someone else’s USB business card into my computer.
(Other netizens responded that this kind of business card is suitable for embedded engineers, but not so much for systems security engineers. 
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