Crypto Prices Tidbyt app

A Pixlet app for the Tidbyt that displays two cryptocurrency tickers on a single static frame: ADA (Cardano) and NIGHT (Cardano's Midnight privacy sidechain token). Prices come from CoinGecko's free public API.

See design-notes.md for layout choices and coin-ID notes (there are multiple tokens called "NIGHT" on CoinGecko; we use midnight-3). Licensed under MIT — © 2026 Brian W Bush.

Setup

1. Enter the dev shell. This flake provides pixlet, yq-go, jq, python3, and curl. Re-enter it after pulling these files so the new tools are on $PATH:

   nix develop
   

2. Create config.yaml from the template:

   cp config-example.yaml config.yaml
   ${EDITOR:-vi} config.yaml
   

   Required: Tidbyt API key, device ID, and an alphanumeric installation ID (Tidbyt's API rejects hyphens/underscores). CoinGecko key is optional — the public free tier is fine at the 5-minute push cadence.

3. Sanity-check sources before deploying:

   ./scripts/check.sh
   

   Confirms CoinGecko responds, prints the current ADA and NIGHT prices + 24h change + market cap, validates the credential set.

4. Preview locally in a browser at http://localhost:8080:

   ./scripts/preview.sh
   

5. One-shot push to the device:

   ./scripts/deploy.sh
   

6. For continuous push (a daemon that re-renders every 5 min), build and run a podman container:

   Ad-hoc with podman run:

   ./scripts/build-container.sh
   ./scripts/run-container.sh                 # foreground; Ctrl-C to stop
   ./scripts/run-container.sh --detach        # background with --restart=always
   ./scripts/run-container.sh --once          # one-shot push for smoke-testing
   

   Declarative with podman kube (recommended for long-running):

   ./scripts/build-container.sh
   podman kube play --replace cryptoprices.yaml
   podman logs -f cryptoprices-tidbyt
   podman kube down cryptoprices.yaml
   

Files

main.star	The Pixlet app (Starlark). Two static rows, both coins visible at once.
flake.nix	Nix dev shell + pixlet derivation + container image.
config-example.yaml	Template. Copy to config.yaml (gitignored).
scripts/check.sh	Pre-deploy sanity check of CoinGecko + credentials.
scripts/preview.sh	pixlet serve for browser preview.
scripts/render.sh	Render one frame to out.webp.
scripts/deploy.sh	Render and pixlet push once.
scripts/build-container.sh	Build the OCI image with credentials baked in.
scripts/run-container.sh	Run the push-daemon container with podman run.
cryptoprices.yaml	Podman kube spec (declarative, recommended).
design-notes.md	Layout rationale, CoinGecko notes, open questions.

Display layout

Both coins share one static frame, two rows each (symbol/price on top, 1h + 24h change below):

┌──────────────────────────────────────────┐
│ ADA               0.1597                 │   row 1: symbol · price (white)
│ -0.49%            -1.41%                 │   row 2: 1h change · day change (color-coded)
│ NIGHT             0.0332                 │   row 3
│ +0.61%            +3.72%                 │   row 4
└──────────────────────────────────────────┘

All text in tom-thumb font. Each row uses Row(main_align="space_between") so the two children sit left and right with the gap absorbing layout slack. Color encoding on row 2 and 4: each timeframe is colored by its own direction (green up, red down, grey missing), so a coin that pumped recently but is down on the day shows green on the left and red on the right — momentum context at a glance.

Percent changes use magnitude-scaled decimals — 3 below 1% (+0.671%), 2 below 10% (-1.41%, +4.80%), 1 below 100% (+12.3%), 0 above (+150%). Trailing zeros are preserved so +4.80% stays +4.80% and adjacent values stack visually.

Data source: CoinGecko's /coins/markets?price_change_percentage=1h,24h endpoint (/simple/price doesn't include 1h).

Caching and rate limits

• http.get(ttl_seconds=300) — the pixlet HTTP cache caps fetches to one per 5 minutes per URL.
• Default push cadence: 5 minutes. CoinGecko's public free tier permits ~30 calls/min, so we're at ~1% of the cap.
• An optional CoinGecko Demo API key (free, from coingecko.com/en/api/pricing) raises the cap further — drop it into config.yaml if you want to.

Notes and caveats

• The Cardano-affiliated NIGHT is CoinGecko ID midnight-3, not midnight — the latter is an unrelated Polygon memecoin (a German Shepherd themed coin) with the same symbol. See design-notes for the deduplication.
• USD prices < $0.0001 fall back to scientific notation in the display.
• 24h change is computed by CoinGecko from the percentage move between rolling 24h-ago and current price — not a UTC-midnight delta. Fine for at-a-glance use.