Intervals — an intervals.icu widget for Garmin watches

A Connect IQ widget with a glance that brings your intervals.icu fitness data to round-screen Garmin watches. Built for and tuned on the Fenix 8 Pro MicroLED (fenix8pro47mm, 454×454, API 6.0); supports 59 device IDs across the Fenix 7/8, Epix 2, Forerunner, Venu, MARQ 2, Descent, Approach and Instinct 3 AMOLED families (layouts scale with screen size; MIP models render the chart palette with fewer colors).

Glance	Form	Load (polar)

HRV ring	Ramp rate ring	Recovery tiles

More: eFTP · steps · sleep · body · fuel

Features

• Glance — a compact banded CTL/ATL chart (the form-zone colors at a glance) with the current form value and data age, right in the widget carousel.
• Form page — big TSB value with zone label, plus Fitness / Fatigue / Ramp rate.
• Polar load chart — CTL and ATL wrapped around the bezel over the time-varying form-zone bands (transition / fresh / grey / optimal / high-risk), computed per angle step from interpolated CTL. The display range auto-fits the data and band envelope; labeled value arcs and 30-day spokes keep it readable. A rectangular variant is available via the Round charts toggle.
• Up to four configurable metric charts — three line/ring slots plus a dedicated ring slot, each choosing from 17 metrics: HRV (rMSSD/SDNN), resting/sleeping HR, ramp rate, eFTP, weight, body fat, VO2max, sleep score/hours, readiness, steps, SpO2, respiration, Baevsky stress index, calories. Radial bar rings (newest day highlighted) or auto-scaled line charts with gap handling for sparse data.
• Stat tile pages — recovery, sleep, body, fuel and subjective wellness rendered as a modern tile grid with vector fonts auto-fitted to their space (no clipped or colliding text on the round display).
• Status page — last sync, athlete, API key state, errors.
• Sync — a background service polls hourly; opening the widget refreshes data older than 15 minutes; START forces a sync. The trend window is fetched in 30-day chunks to stay inside the watch's HTTP response limit.

Requirements

• A free intervals.icu account and its API key (intervals.icu → Settings → Developer Settings).
• Garmin Connect IQ SDK ≥ 6 (built with 9.2) and a Java runtime (brew install --cask connectiq and brew install openjdk on macOS).
• Device files for fenix8pro47mm, downloaded once via the Connect IQ SDK Manager (brew install --cask connectiq-sdk-manager, requires a free Garmin developer login).

Build

./build.sh                  # debug build -> bin/intervals-widget.prg
./build.sh --release
DEVICE=fr955 ./build.sh     # debug build for another supported device
./build.sh --export         # beta store package (beta app ID)
./build.sh --export-prod    # production store package (its own app ID,
                            # since each store listing needs a unique one)

The script locates the SDK (Homebrew cask or SDK Manager install), generates a signing key on first run, and — if a git-ignored .apikey file exists in the repo root — bakes its contents in as the default apiKey property so a sideloaded build needs no further configuration:

echo -n "your-intervals-api-key" > .apikey   # optional, never committed

Without .apikey the key must be set in the app settings (Connect IQ phone app for store installs, or the simulator's settings editor).

Install on the watch

Connect the watch via USB (MTP — use Android File Transfer or OpenMTP on macOS) and copy bin/intervals-widget.prg into /GARMIN/Apps/. Restart the watch; the glance appears in the carousel.

Settings

Setting	Default	Notes
intervals.icu API key	–	from intervals.icu Developer Settings
Athlete ID	0	0 = the key's owner; coaches can use i12345 IDs
Glance display	fit+fat+form	or fitness / fatigue / form only
Form as % of fitness	off	switches the form value AND zone scale; off = absolute TSB points (intervals.icu default)
Round charts	on	polar load chart + ring metric charts
Chart window	3 months	6 weeks / 3 months / 6 months
Chart 1–3	HRV, ramp rate, eFTP	line/ring chart slots
Ring chart	steps	dedicated radial bar chart
Show … page	all on	hide form / recovery / sleep / body / fuel / feel / status

Simulator

SDK=~/Library/Application\ Support/Garmin/ConnectIQ/Sdks/connectiq-sdk-mac-*
$SDK/bin/connectiq                                  # start simulator
$SDK/bin/monkeydo bin/intervals-widget.prg fenix8pro47mm

Set the API key via File → Edit Persistent Storage → Edit Application.Properties, and trigger a background sync with Simulation → Background Events → Temporal Event. Note the simulator preserves app settings across reinstalls — delete GARMIN/APPS/SETTINGS/INTERVALS-WIDGET.SET from the simulator's temp filesystem if changed property defaults don't seem to apply.

How it talks to intervals.icu

Authentication is HTTP Basic with the literal username API_KEY and your personal key as the password. Two request flavors hit GET /api/v1/athlete/{id}/wellness with a fields= filter (which also strips nulls, keeping payloads small for the watch):

1. the last 7 days of every displayed wellness metric, collapsed to the most recent non-null value per field;
2. the chart window of ctl,atl plus the selected chart metrics, fetched in ≤30-day chunks (a 90-day response with sportInfo exceeds the watch's response buffer).

Form (TSB) is computed as ctl − atl. The zone coloring and chart bands use absolute TSB thresholds (+20 / +5 / −10 / −30) by default, matching intervals.icu's coloring; the "Form as % of fitness" setting switches both the displayed value and the zone scale to percent-of-CTL, matching the equivalent intervals.icu option. eFTP comes from the wellness sportInfo array (first sport entry).

Please be polite to the API — the widget syncs hourly in the background and on-demand, which is well within what the intervals.icu folks ask of clients.

License

MIT