# MTG RFID Companion
A hand-held **Magic: The Gathering** companion built on an **ESP32-WROOM-32**. Tap an RFID/NFC-tagged card to a built-in reader and the device:
- renders the card's cover art and metadata on a **2.0" ST7789 TFT (240x320)**,
- flashes a **WS2812B Neopixel** in the card's mana color and plays a short **buzzer** chirp,
- keeps a **life counter** (20/40) you adjust with a rotary encoder,
- caches cards locally on **LittleFS** and refetches from the **Scryfall API** over Wi-Fi,
- runs a **SoftAP registration server** (`MTG-Companion`) so you can pair an unknown tag to a card name from your phone.
All code is **pure ESP-IDF v5.x (C) / FreeRTOS** β no Arduino.
---
## Features
| | |
| :--- | :--- |
| π RFID scanning | MFRC522, NTAG21x / MIFARE tags, 4- and 7-byte UIDs |
| π₯οΈ Display | ST7789 240x320 RGB565, 5x7 text, scaled digits, streaming JPEG decode |
| π Network | Wi-Fi STA auto-connect, Scryfall HTTPS with local cache |
| π‘ Pairing | SoftAP `MTG-Companion` (192.168.4.1) web SPA for UID β card name |
| π UX | EC11 rotary encoder, backlit life counter, mana-colored LED, audio cues |
| πΎ Storage | LittleFS `/spiffs` (~1.9MB) seeded with card mapping + example art |
---
## Hardware Requirements
- **ESP32-WROOM-32** dev board (4MB flash, no PSRAM required)
- **MFRC522** RFID reader (13.56 MHz, SPI)
- **ST7789** SPI TFT, 240x320 (e.g. common 2.0-2.4" breakout)
- **EC11** rotary encoder with push switch
- **WS2812B / Neopixel** (single LED)
- **Passive piezo buzzer**
- Antenna-friendly **NTAG213/NTAG215** stickers or MIFARE cards, ~3.3Vβ5V supply
---
## Wiring Guide
> **Do not change these GPIO assignments in code** unless you update both
> `main/hw_pins.h` and this table. The ST7789 and MFRC522 **share one SPI bus** (SPI2_HOST).
### Pin map
> **Display and reader are on two separate SPI controllers:** the ST7789 on
> **SPI2_HOST (VSPI)**, the MFRC522 on **SPI3_HOST (HSPI)** β so the panel and
> the RFID reader never share bus timing.
| Peripheral | Function | ESP32 GPIO | Notes |
| :--- | :--- | :---: | :--- |
| **ST7789** (7-pin) β SPI2_HOST | SCL | **18** | SPI2 (VSPI) clock |
| | SDA | **23** | SPI2 MOSI (data) |
| | CS | **21** | dedicated chip select (non-strapping pin) |
| | DC | **19** | data/command (non-strapping pin) |
| | RST | **4** | panel reset |
| | VCC / GND | 3.3V / GND | panel power (no separate LED pin) |
| **MFRC522** β SPI3_HOST | SCK | **16** | SPI3 (HSPI) clock (own bus) |
| | MOSI | **17** | SPI3 data out |
| | MISO | **13** | SPI3 data in |
| | SDA (CS) | **26** | dedicated chip select |
| | RST | **22** | hard reset |
| | 3.3V / GND | β | feed from board 3.3V rail |
| **EC11** | CLK | **32** | interrupt input, pull-up |
| | DT | **33** | quadrature B |
| | SW | **25** | button, active low, pull-up |
| **WS2812B** | DIN | **27** | RMT Tx; supply 5V/VDD, GND common |
| **Buzzer** | SIG | **14** | LEDC PWM |
### Suggested breadboard layout
```
ESP32-WROOM-32
ββββββββββββββββββββββββββββββ
β 3V3 16 ββ SCK βββββββββ β
β GND 17 ββ MOSI βββββ β β
β 13 ββ MISO βββββΌβββ β
β 26 ββ SDA(CS) ββ β
β 22 ββ RST ββ β
β 21 ββ CS βββΌββββββββ€ ST7789 (7-pin)
β 19 ββ DC βββ€ β SCL = 18, SDA = 23
β 4 ββ RST ββ β VCC = 3V3, GND = GND
β 18 ββ SCL ββββββββββ
β 23 ββ SDA βββββββββ (display = SPI2)
β 32 ββ CLK βββββββββ€ EC11 33 ββ DT 25 ββ SW/GND
β 27 ββ Din βββββββββ€ WS2812B (5V + GND)
β 14 ββ SIG βββββββββ€ Buzzer (GND)
ββββββββββββββββββββββββββββββ
```
> **MFRC522 (own SPI3/HSPI bus):** SCKβ16, MOSIβ17, MISOβ13, SDA(CS)β26,
> RSTβ22, VCCβ3.3V, GNDβGND. It shares **no lines** with the display.
>
> **ST7789 (SPI2/VSPI):** SCLβ18, SDAβ23, CSβ21, DCβ19, RSTβ4, VCCβ3.3V, GNDβGND.
>
> CS (GPIO21) and DC (GPIO19) are deliberately **not** strapping pins, so the
> panel can stay connected during `idf.py flash`. (The old GPIO15/GPIO2
> assignment made the panel hold boot-strap lines and block flashing.)
- Keep SPI signal runs short (< 10 cm) for reliable 20 MHz display transfers.
- NTAG213/215 FPC stickers need to sit flat and close to the MFRC522 antenna.
- The **WS2812B** draws up to ~60 mA; power it from the 5V rail, never from a GPIO.
---
## Getting Started
### 1. Toolchain
Install ESP-IDF **v5.5** (any 5.x works): https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/
Verify:
```powershell
# Windows (Espressif "ESP-IDF 5.5 PowerShell" terminal)
. C:\Espressif\Initialize-Idf.ps1 # or: . $IDF_PATH\export.ps1
idf.py --version
```
> **Never used Espressif tools before? Skip ahead to
> "[Changing the Wi-Fi without the toolchain](#changing-the-wifi-without-the-toolchain)";**
> the section below is optional.
### 2. Build
```powershell
idf.py set-target esp32
idf.py build
```
The custom partition table (`partitions.csv`) reserves:
| Offset | Size | Subtype | Purpose |
| :--- | :--- | :--- | :--- |
| 0x10000 | 2 MB | app/factory | firmware |
| 0x210000 | ~1.9 MB | data/littlefs | `/spiffs` cache (seeded from `storage/`) |
### 3. Configure Wi-Fi
Two equivalent ways:
```powershell
# a) interactive menu (recommended)
idf.py menuconfig # -> "MTG RFID Companion" -> SSID + password
# b) edit the preset file directly
# sdkconfig.defaults.esp32
```
Leaving the SSID empty (or keeping the `YOUR_...` placeholders) **disables
station mode**. The SoftAP pairing server runs regardless, so the device stays
usable as a fully standalone scanner β no home network required.
#### What "station mode disabled" actually means
The Wi-Fi radio still turns on, but only as an access point:
1. `wifi_manager_start()` sees the blank/placeholder SSID and returns early β
it never calls `esp_wifi_connect()`, so the device won't try to join any
router (and won't pretend to be online).
2. `web_server_start()` starts unconditionally: SoftAP **`MTG-Companion`** at
`192.168.4.1` (own DHCP) plus the `/api/last_uid` and `/api/bind` endpoints.
3. `net_task` skips the 60-second connect wait **and** the boot-time prefetch.
Card lookups only run when you explicitly trigger one, and those fail fast
(no internet route) with a `scryfall` log line β they never block the UI.
#### What works and what doesn't
| Feature | In AP-only mode | Notes |
| :--- | :--- | :--- |
| RFID scanning, life counter, LED/buzzer | β | fully local |
| Showing **already-cached** cards (art + stats) | β | served from `/spiffs` |
| Binding a UID to a card name | β | written to `/spiffs/mappings.json` immediately |
| **Scryfall lookup + art download** | β | the device has no internet here; the fetch fails and is logged. It completes automatically on a later boot **with Wi-Fi configured** β the boot-time prefetch walks `mappings.json` and downloads anything missing |
| Scryfall autocomplete in the pairing page | β οΈ | the AP doesn't pass internet through (no NAT). A phone with **cellular data keeps its mobile connection**, so autocomplete works there; on a device with no other internet path, type the exact card name manually |
> **Use case:** AP-only mode is the normal "deck on the table" flow β mid-game
> you almost never need live Scryfall lookups. When you do (new card, missing
> art), configure Wi-Fi once, boot briefly, and the binding + art cache update
> themselves via prefetch.
---
## Changing the Wi-Fi without the toolchain
> **If you're new to this and haven't installed any Espressif software yet,
> start here.**
The Wi-Fi network the device connects to is **baked into the firmware at
compile time** β there is no on-device settings menu yet. To change it you
must edit one text file and produce a new firmware image. Here is the shortest
ESPRESSIF-FREE path to do that, with zero drivers or toolchains.
### The one file you edit
Open **`sdkconfig.defaults.esp32`** in any text editor (Notepad is fine) and
find these two lines:
```
CONFIG_MTG_WIFI_SSID="YOUR_SSID_HERE"
CONFIG_MTG_WIFI_PASS="YOUR_PASSWORD_HERE"
```
Replace the placeholders with **your** network name and password, keeping the
quotes:
```
CONFIG_MTG_WIFI_SSID="MyHomeWiFi"
CONFIG_MTG_WIFI_PASS="correct horse battery staple"
```
- Keep the file **UTF-8 without BOM**, and don't add spaces inside the quotes.
- If your password has a `"` or `\` in it, this file format can't represent it
(rare) β pick that one character out of the password or use the toolchain
menu instead.
- Want to go back to offline-only later? Restore the `YOUR_...` placeholders
and rebuild.
### Getting a new firmware image from this file
The repo cannot build firmware without the toolchain. Your options, easiest
first:
| Path | What's needed | How |
| :--- | :--- | :--- |
| **Ask whoever gave you the device** | a minute of their time | Send them the edited file; they run `idf.py build` and hand you a new `.bin` |
| **One-time toolchain install (~45 min, guided)** | the Espressif installer (free, Windows/macOS/Linux) | Follow the official guide: then run the 5 commands in [Build](#2-build) |
| **CI build** (GitHub Actions etc.) | a GitHub account | The repo can build on `ubuntu` in CI; push the edited file and download the built `mtg-rfid-companion.bin` artifact |
### Flashing the new firmware (no toolchain needed)
Flash using **Espressif Flash Download Tool** (graphical, no toolchain):
or `esptool.py` if you already have Python:
```
pip install esptool
esptool.py -p COM3 --chip esp32 --before default_reset write_flash --flash_mode dio --flash_size 4MB 0x1000 bootloader.bin 0x8000 partition-table.bin 0x10000 mtg-rfid-companion.bin
```
### TL;DR
1. Edit `sdkconfig.defaults.esp32` β 2. rebuild (yours or someone's toolchain) β
3. flash the `.bin` β 4. done. If you don't need your home Wi-Fi, **skip the
whole thing**: the device works standalone and has its own AP.
---
### 4. Flash & watch
```powershell
idf.py -p COMx flash monitor # COMx = your serial port
```
Expected boot log if everything is wired right:
```
I storage: LittleFS mounted at /spiffs: bytes total ...
I storage: boot_count read back = 1 (persistence across reboots OK)
I rfid: RC522 polling task pinned to Core 0
I display: ST7789 240x320 ready ...
I web: SoftAP 'MTG-Companion' at 192.168.4.1, web server ready
I ui: UI task on core 1
```
> **RFID reader missing / not wired? That's OK.** A reader self-test failure no
> longer aborts boot β the device logs a warning and continues into the display,
> SoftAP and web-pairing screens without card scanning:
---
## Usage
### Scan a card
Place a tagged card on the reader:
1. **Mapped UID** β chirp, mana-colored LED flash, then the card view (cover art + name/type/PΒ·T/price/mana).
2. **Unknown UID** β registration screen with the pairing address.
### Life counter
Press the encoder button to toggle **SCANNER β LIFE_COUNTER**. Rotate to adjust
(20/40 preset or whatever you last set; press again to reset to the preset).
### Web pairing (registration mode)
1. Connect your phone to the `MTG-Companion` access point. A phone with
cellular data keeps its mobile internet, so Scryfall autocomplete works;
otherwise type the name manually.
2. Open `http://192.168.4.1`.
3. Scan an unmapped card β the UID appears in the page.
4. Type / pick a Scryfall-autocomplete name β **Pair UID with card**.
5. The mapping persists to `/spiffs/mappings.json`. The card data/art fetch
runs immediately if the device has Wi-Fi, or is picked up automatically by
the boot-time prefetch the next time you boot with Wi-Fi configured.
---
## Storage Layout (`/spiffs`)
```
/spiffs/
βββ mappings.json UID -> Card Name map
βββ cards/
β βββ sample.json example metadata
β βββ sample.jpg example cover art (baked into flash image)
β βββ .json Scryfall metadata cache
β βββ .jpg cached cover art
```
The `storage/` folder is compiled into the LittleFS partition image at build
time (`littlefs_create_partition_image`), so a fresh flash already contains
`mappings.json` and the example art.
---
## Troubleshooting
| Symptom | Fix |
| :--- | :--- |
| Display = black / garbage | Check CS/DC/RST wiring; try toggling `esp_lcd_panel_invert_color` and `LCD_RGB_ELEMENT_ORDER_*` in `display_manager.c` |
| Colors inverted | Same toggle as above β panel clones differ |
| No UID printed on scan | Verify MFRC522 wiring, tag type (ISO14443A), antenna positioning; confirm `rfid: RC522 polling task pinned to Core 0` in the log |
| Boot log: `rc522: FIFO length missmatch` / `RTOS: RFID unavailable` | Reader self-test failed. Check the MFRC522 has 3.3V power (many clones have a separate power pin), CS=GPIO26 / RST=GPIO22, SCK/MOSI/MISO=16/17/13 on its own SPI3 bus. Try lowering `RC522_SPI_CLK_HZ` in `rfid_manager.c` (e.g. `1000000`); the skip-self-test option (`CONFIG_MTG_RFID_SKIP_SELFTEST`) lets scanning start anyway |
| Wi-Fi never connects | Re-run `idf.py menuconfig`, confirm you replaced the `YOUR_...` placeholders |
| Scryfall autocomplete shows nothing | The AP has no internet passthrough β the phone needs its own mobile data connection, or type the card name manually |
| Can't reach 192.168.4.1 | Ensure your phone joined `MTG-Companion`, not a cached network |
| Flash fails: `Serial data stream stopped` | If the ST7789 is wired with CS=GPIO15 / DC=GPIO2 (the old strap-pin assignment), disconnect/power-down the display during `idf.py flash` β the panel holds the boot-strap lines at reset and corrupts the serial link. With the current recommended wiring (CS=GPIO21, DC=GPIO19, both non-strapping) the display can stay connected. |
| RFID step of boot log: `Buffers content missmatch`, buffer2 = `13 33 37` | The reader answers (SPI OK) but the PCD self-test is flaky on clones. RST can stay unconnected (`-1`), the clock is already 1 MHz; confirm the MFRC522's dedicated power header gets a clean 3.3V and that MISO=GPIO13 is actually connected |
| Card renders but no art | Card not cached yet β check `scryfall` log lines; art downloads are best-effort |
| App grows near 2MB | mbedTLS + HTTP pulls are large; if needed, enable `CONFIG_MBEDTLS_CERTIFICATE_BUNDLE` (smaller) |
---
## Project Layout
```
βββ CMakeLists.txt top-level; bakes LittleFS storage image
βββ partitions.csv custom partition table
βββ sdkconfig.defaults shared ESP32 defaults
βββ sdkconfig.defaults.esp32 Wi-Fi credential preset (edit me)
βββ storage/ files pre-seeded into /spiffs
βββ tools/ host-side helpers (sample JPEG generator)
βββ main/
βββ hw_pins.h GPIO assignments (authoritative)
βββ spi_bus_manager.c shared SPI2_HOST bus
βββ storage_manager.c LittleFS mount + JSON helpers
βββ rfid_manager.c MFRC522 / Core 0 polling
βββ display_manager.c ST7789 + fonts + streaming JPEG
βββ ui_task.c state machine + screens (Core 1)
βββ wifi_manager.c STA connect/reconnect
βββ scryfall_client.c Scryfall HTTPS + cache (net_task)
βββ web_server.c SoftAP pairing server
βββ encoder.c EC11 ISR decode
βββ led_manager.c WS2812B RMT
βββ buzzer.c LEDC PWM tones
βββ app_state.c shared app/life-counter state
```
See `AGENTS.md` for the detailed architecture, core split, and coding
conventions used across this repository.