NFC Stitch

Production Steps
: 1. Open LCSC EDA and create a new project. Enter the schematic drawing stage. We selected NXP's NT3H2111W0FHK chip, which uses an XQFN-8 package.
 
The above are the chip pin definitions (because I checked and found that the pin definitions of NT3H1101 and NT3H2111 are the same, I selected NT3H1101 in the schematic).
In this design, since the card does not need to implement external control, the information transmission mainly exists between the NTAG chip and the touch device. The energy obtained by the NTAG chip is transferred to the LED to light up the LED for display. Therefore, VOUT and VCC are directly shorted, and EP, FD, SCL, and SDA are all left floating.
The completed schematic is as follows:
2. NXP's RF antenna design
manual provides several different coil shapes. I referenced the antenna design at https://www.instructables.com/PCB-Business-Card-With-NFC/ (the specific calculations are also mentioned in the article; interested readers can research it themselves, and I won't repeat them here). The article provides an Excel document for coil parameter calculations.
3. Convert the schematic to a PCB. Add the image you want to draw on the PCB to the document layer, adjust the expected size, and enter the coil size you can design in the Excel file mentioned earlier. Note that this should not exceed JLCPCB's processing capabilities. Adjust the component positions. I expect the flower above the coil to light up when it's near the coil (also for easy testing of functionality after soldering).
4. Connect the circuitry. Place the drawn coil on one side of the PCB.
5. Draw the outline. In the board outline layer, select polyline, and draw the arc according to the edge of the selected image. Refer to the video at https://b23.tv/t66PeZp.
At this point, the PCB is basically complete. Export the Gerber file and use JLCPCB's order assistant to fabricate the board. (Purchase components according to the BOM)
6. After receiving the PCB, you will need the following tools: solder paste, hot air gun, board cleaner, and tweezers (be careful when using the equipment for soldering).
7. Download NXP's writing software, TagWriter, from the NXP website (the chip needs to be formatted before use; click the Clear Tag button - Erase and Format to NDEF).
8. Click Write Tag, follow the prompts, and you'll have a fun Stitch keychain!
(Stitch image from the internet; please contact me to remove it if there is any copyright infringement.)