dynamic nfc business card

Description

0x0630ff PCB Business Card
Using ESP32-C3 + ST25DV16K

This handy creation is great for those looking for a job while needing to maintain two or more personalities or emails. Even if you only have one email or one phone number like most sane people, this device is still going to be a fun way to learn about NFC and low power device design. All while giving the smallest amount of effort trying to look like some high tech cyberpunk gizmo. To keep it as thin as possible, USB connectors were eliminated. In the next revisions, slimming the display connection and battery connections will be the priority. Programming will be done via UART connections broken out to through hole pins.

Goals for this device include
- Use as an NFC tag
- BLE and WiFi connection
- Update the NFC stored data via wireless or user input
- 3 button interface
- OLED display
- Longest possible battery life
- Re-chargable
- Ability to experiment with NDEF payloads for 7h3 h4ck3r 1n 4ll 0f u$.

Details

MCU: ESP32-C3FH4

Datasheet: https://www.espressif.com/sites/default/files/documentation/esp32-c3_datasheet_en.pdf

NFC IC: ST25DV16K

Datasheet: https://cdn-learn.adafruit.com/assets/assets/000/093/906/original/st25dv04k.pdf?1596828496

Board thickness: 0.062" (1.6mm)

Layer count: 4

NFC Coil turn count: 10

Pinout:

Left button: GPIO9 (Boot button)

Center button: GPIO8

Right button: GPIO3

SDA: GPIO18

SDL: GPIO19

NFC_INT: GPIO1

Google Gemini helped provide a brief description of NDEF for me:

The Near Field Communication (NFC) Data Exchange Format (NDEF) serves as the foundation for communication between NFC-enabled devices. It defines a standardized structure for encoding data onto NFC tags and facilitates the exchange of information during close-range interactions (typically a few centimeters). NDEF messages function similarly to data packets, encapsulating one or more records that specify the type and content of the information being transmitted.

Each NDEF record comprises two key components: a header and a payload. The header offers crucial metadata about the record, including its type (text, URI, etc.), length, and optional identification details. The payload itself contains the actual data being transmitted, which can range from simple text strings to more complex formats like URLs or contact information. By adhering to the NDEF structure, NFC devices can interpret the data correctly and perform the intended actions, such as launching a web page upon tag interaction.

Project Logs

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Adding display and battery power.
0x0630ff • 06/10/2024 at 17:05 • 0 comments

Did anyone really think there would be zero mistakes?

Turns out I got the display pins rotated the wrong way, oops....

The device is shown running a test sketch that cycles through some preset NDEF messages to update the NFC data with. Left and right buttons change the URI message and the center button commits the data to the IC. By using the proper URI protocol, the receiving device can recognize phone numbers to call, emails to send a message to, and URLs to open in the default browser with.

I added some jumper wires to get the display spun the right way. Looks alright enough to keep going with rev1 of this project. Adds a lot to the thickness unfortunately. In the end, this will be soldered in place as flat as possible. It looks much nicer top down where you cannot tell how tall the display sits.

Here is a side view of the device. the battery is much thicker than the end goal but for testing this is working out well. It fits in my pocket without any problems (aside for being stabbed by the programming pins still soldered in place). The battery can be charged via the programmer's input power pin. The end goal is to find a paper thin Li-Po for the bottom side to keep the entire thickness down (I found a company "PowerSteam" that offers some viable choices). Obviously, getting the display connection correct will also help reduce that thickness.
need to figure out power problem
0x0630ff • 06/01/2024 at 03:35 • 0 comments

Unsure exactly what the issue is. Unable to get enough power through the UART TTL programmer into the charge and regulator circuit. Bypassing the charge circuit for the time being to work on programming the device and ensure all parts are working as expected. I know the programmer isn't intended to deliver a lot of power but surprised this isn't working since I used an identical circuit in other functional projects. Could be component selection. Will explore this later. Also planning to use pogo-pins for programming (4 pin header for now...)

The on off switch I chose is easily stuffed up with flux after some rework. Boot button also seems to occasionally have this issue as well. Will need to be careful when doing rework, or buy extra parts..

I was successfully able to update the NFC chip via i2c from the ESP32-c3 to share URL data. Hoping to spend time learning more about the various messages able to share using NDEF. It is covered by the display once everything is soldered. Initial tests will use a board to board connector just in case I need to rework the NFC IC, however it seems to work fine, so far...
The boards are here!
0x0630ff • 05/22/2024 at 05:29 • 0 comments

PCB's arrived. Still waiting for ESP32-C3 and ST25dv16k IC's since JLCPCB didn't have the specific part number I planned to use. Those should arrive tomorrow and I will solder them on as soon as possible. Crossing my fingers this works right away....
20240519
0x0630ff • 05/20/2024 at 04:26 • 0 comments

PCBA ordered. ETA ~5 days.