Rust firmware for the GeekMagic SmallTV PRO (ESP32-WROOM-32) that displays your Claude Code token and request rate-limit usage on the built-in 240×240 ST7789 display.
Inspired by Clawdmeter. Instead of a BLE + Python daemon, the ESP32 polls the Anthropic API directly over WiFi.
| Part | Details |
|---|---|
| MCU | ESP32-D0WDQ6 rev1.0 (dual-core, 240 MHz, 520 KB SRAM, no PSRAM) |
| Display | ST7789, 240×240, SPI Mode 3 |
| Crystal | 40 MHz |
| Device | GeekMagic SmallTV PRO v02-22 |
| GPIO | Function | Notes |
|---|---|---|
| 18 | SPI CLK | VSPI default |
| 23 | SPI MOSI | VSPI default |
| 3 | SPI CS | also UART0 RX — see note below |
| 2 | Display DC | |
| 4 | Display RST | |
| 21 | Backlight | high = on |
Alternative pinout: some board revisions use CLK=14, MOSI=13 (HSPI). If the display stays blank, change those two lines in
src/main.rs.
GPIO3 note: GPIO3 doubles as UART0 RX (serial input from host) and SPI CS. Serial input is only possible before the display is initialized. After that, token updates are done over WiFi.
cargo install espup
espup install
. $HOME/export-esp.sh # add to your shell profilecargo install espflashNo credentials needed at build time.
cargo build --release
espflash flash target/xtensa-esp32-espidf/release/clawdmeter-rs --monitor
# or:
./flash.shOn first boot the device has no WiFi config. Open espflash monitor (or any serial terminal at 115200 baud) before or immediately after powering the device. You will be prompted:
I (...) clawdmeter_rs: === No WiFi config. Enter credentials in serial monitor ===
I (...) clawdmeter_rs: SSID:
MyNetwork
I (...) clawdmeter_rs: Password:
mysecret
WiFi credentials are saved to NVS and survive reboots. To reconfigure, erase NVS:
espflash erase-flash # wipes everything; reflash firmware afterwardsThe token is your Claude Code OAuth access token. Find it on the machine where Claude Code is installed:
python3 -c "import pathlib,json; print(json.loads(pathlib.Path('~/.claude/.credentials.json').expanduser().read_text())['claudeAiOauth']['accessToken'])"Once the device is on Wi-Fi, the IP address is shown on the display and logged to serial. Send the token from any device on the same network:
curl -X POST http://<device-ip>/token -d "sk-ant-oat01-..."The token is saved to NVS and used immediately. Update it the same way whenever the key rotates.
| Crate | Role |
|---|---|
esp-idf-hal |
SPI, GPIO, UART, delay |
esp-idf-svc |
WiFi, HTTPS (mbedTLS), HTTP server, NVS |
embedded-graphics |
2D drawing primitives, fonts |
No external display driver library — ST7789 is driven directly to avoid version-compatibility issues between embedded-hal 1.0 and the mipidsi/display-interface ecosystem.
main loop (every 60s)
└── api::fetch_usage() POST /v1/messages (1 token, haiku)
└── parse anthropic-ratelimit-unified-* headers
└── ui::draw_usage() render bars + countdown to display
HTTP server (background, port 80)
└── POST /token update Anthropic token in NVS
The API call sends a minimal max_tokens: 1 request to claude-haiku-4-5 purely to receive the anthropic-ratelimit-unified-* response headers. The actual response content is discarded.
| Symptom | Fix |
|---|---|
| Display blank | Try CLK=14, MOSI=13 in src/main.rs |
| Display colors wrong | Toggle INVON in display.rs::init() |
| Display rotated | Change MADCTL byte in display.rs::init() |
| TLS handshake fails | Ensure CONFIG_MBEDTLS_CERTIFICATE_BUNDLE=y in sdkconfig.defaults |
| Serial prompt not appearing | Open monitor before powering the device |
| Can't type in serial prompt | Must open monitor before display init (GPIO3 conflict) |
| Token not updating | Check device IP in serial logs; ensure same network |