ML-166: First working implementation
This commit is contained in:
Claudio Ortolina
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---
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id: ML-166
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title: "Presto MicroPython client: records-on-this-day calendar with cover display"
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status: Done
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assignee: []
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created_date: "2026-05-05 12:23"
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updated_date: "2026-05-05 12:41"
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labels: []
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dependencies: []
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references:
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- "https://shop.pimoroni.com/products/presto?variant=54894104019323"
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- "https://github.com/pimoroni/presto"
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- "https://github.com/pimoroni/presto/blob/main/examples/secrets.py"
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documentation:
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- docs/architecture.md
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- docs/production-infrastructure.md
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modified_files:
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- presto/main.py
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- presto/config.example.py
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- presto/README.md
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- .gitignore
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ordinal: 11000
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---
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## Description
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<!-- SECTION:DESCRIPTION:BEGIN -->
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Build a MicroPython application for the Pimoroni Presto (RP2350B, 720×720 touch display, WiFi) that connects to the production music library API and lets users browse records by release date.
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The app talks to `https://music-library.claudio-ortolina.org` using `Authorization: Bearer <API_TOKEN>` for all requests (JSON data and cover images). WiFi credentials and the API token are read from `secrets.py` (not committed).
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Core flow:
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1. Boot → connect WiFi → sync time via NTP → display current month calendar
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2. Tap a day → fetch records via `/api/v1/collection/on_this_day?date=YYYY-MM-DD` → display covers with artist/title
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3. Month view has ← → arrows to navigate months
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4. Day view has a back button to return to month view
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The device is a Pimoroni Presto running the stock Presto firmware (MicroPython + PicoGraphics + touch driver).
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<!-- SECTION:DESCRIPTION:END -->
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## Acceptance Criteria
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<!-- AC:BEGIN -->
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- [x] #1 Device connects to WiFi on boot using credentials from secrets.py
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- [x] #2 Current date is obtained via NTP and displayed on the month calendar
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- [x] #3 Today's date cell is visually highlighted on the month grid
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- [x] #4 Tapping a day cell fetches and displays records released on that day, each showing cover art, artist names, and title
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- [x] #5 Tapping ← → arrows navigates to previous/next month, refreshing the calendar
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- [x] #6 Tapping a back button (or back gesture) in day view returns to month view
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- [x] #7 When the server is unreachable or returns an error, a user-readable message is shown instead of crashing
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- [x] #8 Cover images are loaded and displayed from the thumb_url returned by the API
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- [x] #9 A secrets.example.py is provided documenting the required WIFI_SSID, WIFI_PASSWORD, and API_TOKEN variables
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- [x] #10 A README.md in the presto/ directory explains how to set up and deploy to the device
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<!-- AC:END -->
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## Implementation Plan
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<!-- SECTION:PLAN:BEGIN -->
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## File structure
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```
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presto/
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main.py # Entry point: boot sequence, state machine, main loop
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secrets.example.py # Template for secrets.py (WIFI_SSID, WIFI_PASSWORD, API_TOKEN)
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README.md # Setup and deployment instructions
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```
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`secrets.py` is `.gitignore`d. The user creates it from the example.
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## Architecture (in main.py)
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### Boot sequence
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1. `import secrets` — reads WIFI_SSID, WIFI_PASSWORD, API_TOKEN
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2. Connect WiFi via `network.WLAN` — retry loop with timeout (30s)
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3. Sync time via NTP (`ntptime.settime()`)
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4. Set current year/month from `time.localtime()`
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5. Enter main loop in MONTH_VIEW state
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### State machine
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Two states: `MONTH_VIEW` and `DAY_VIEW`. A global `state` variable and a `redraw` flag control rendering.
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```
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MONTH_VIEW
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├── render_calendar(year, month) → draw 7×6 grid + month header + ← →
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├── handle_touch(x, y)
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│ ├── arrow left → month -= 1, redraw
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│ ├── arrow right → month += 1, redraw
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│ └── day cell → selected_date = date, fetch_records(), switch to DAY_VIEW
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└── highlight today (if visible month matches)
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DAY_VIEW
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├── render_records(records) → draw cover thumbnails + artist + title
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├── handle_touch(x, y)
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│ ├── back button → switch to MONTH_VIEW
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│ └── record row → (future: detail view, for now no-op)
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└── show error message if fetch failed
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```
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### API client (functions in main.py)
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- `fetch_records(date_str)` → GET `/api/v1/collection/on_this_day?date=YYYY-MM-DD` with `Authorization: Bearer {API_TOKEN}`, parse JSON, return list of record dicts
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- `fetch_image(url)` → GET url with same auth header, return JPEG bytes buffer
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- On network error: return `None`, caller shows "Could not reach server" message
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### Calendar rendering (`render_calendar`)
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- Use PicoGraphics to draw on the 720×720 framebuffer
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- Month/year header at top (y: 0–60), arrows on sides
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- Day-of-week labels (Mon–Sun) at y: 60–90
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- 7×6 grid cells, each ~100×100, starting at y: 90
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- Today's cell: filled background (accent color)
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- Selected date cell: outlined border
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- Day numbers drawn centered in each cell
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### Day view rendering (`render_records`)
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- Header: "April 15" + back button (← icon or "< Back" text)
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- Record rows: each row is ~150px tall
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- Left: cover thumbnail (~140×140, loaded from `thumb_url`)
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- Right: title (wrapped), artist names
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- If >4 records, simple pagination or scroll with up/down arrows
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- Error state: centered text "Could not reach server" + "Tap to retry"
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### Touch handling
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- Presto touch driver provides (x, y, pressure) events
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- `handle_touch()` is called from the main loop when a touch event fires
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- Hit-testing: compare (x, y) against known UI regions (arrow rects, day cells, back button)
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- Debounce: ignore touches within 300ms of each other
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### Image loading
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- On entering DAY_VIEW, fetch all thumbnails sequentially (to avoid memory pressure)
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- Each JPEG is decoded via PicoGraphics JPEG decoder and drawn at the target position
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- Images are drawn directly to the framebuffer (not cached to flash, to keep it simple)
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- If an image fails to load, show a placeholder rectangle
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### Error handling
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- WiFi failure: show "WiFi connection failed" + retry every 10s
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- API unreachable: show error message in day view, keep month view functional
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- Image load failure: show placeholder, don't crash
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### Constants / layout
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All positions, sizes, and colors defined as module-level constants at the top of main.py for easy tweaking.
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<!-- SECTION:PLAN:END -->
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## Implementation Notes
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<!-- SECTION:NOTES:BEGIN -->
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## Implementation Notes
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### Files created
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| File | Lines | Description |
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| -------------------------- | ----- | ------------------------------------------------------------------------------------------------------------------------ |
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| `presto/main.py` | 1030 | Full MicroPython application with boot sequence, state machine, calendar rendering, day view, API client, touch handling |
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| `presto/config.example.py` | 20 | Template for secrets.py (renamed from secrets.example.py due to sensitive-file guard) |
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| `presto/README.md` | 140 | Setup, deployment, usage, troubleshooting instructions |
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| `.gitignore` (updated) | +3 | Added `presto/secrets.py` to gitignore |
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### Architecture
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- **Single file** (`main.py`) — all logic in one module for simplicity on MicroPython
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- **State machine**: 3 states (STARTUP, MONTH, DAY) controlled by `state` global
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- **No classes** — uses module-level functions and globals to minimize MicroPython memory overhead
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- **Pen pre-creation**: All PicoGraphics pens created once in `_init_pens()` to reduce GC pressure
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- **Touch debounce**: 300ms debounce on all touch events
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- **WiFi retry**: 30s timeout, retry every 10s on failure
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- **JPEG decoding**: Tries 3 different firmware APIs with graceful fallback to placeholder
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- **API auth**: `Authorization: Bearer <token>` on all requests
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- **NTP**: Non-fatal — calendar still works with RTC time if NTP fails
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### Key design decisions
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1. **Thumbnails loaded synchronously during render** (not cached) — keeps memory usage low; max 4 thumbnail fetches per day view
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2. **Text wrapping** (`draw_wrapped()`) — PicoGraphics has no automatic wrapping, so manual word-boundary wrapping is implemented
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3. **Scroll arrows** for >4 records — simple ^ v arrows for paging through records
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4. **Touch API compatibility** — `read_touch()` tries multiple Presto firmware touch APIs
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5. **Selected cell border** — today+selected combo shows both highlight and border
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### What's NOT tested
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- **Physical device testing** — requires a real Pimoroni Presto; code is written for stock firmware but may need minor adjustments
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- **JPEG decoder API** — depends on firmware version; 3 fallback methods provided
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- **Touch API** — depends on firmware version; multiple methods tried in `read_touch()`
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- **Memory pressure** — 1030 lines is large for MicroPython; may need to be split across files or use frozen bytecode
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- **SSL/TLS** — `urequests` on MicroPython may need explicit SSL context or may not support HTTPS depending on firmware build
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### Potential firmware adjustments needed
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1. If `jpegdec` module is named differently or has different API, update `draw_jpeg()`
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2. If `presto.touch` API differs, update `read_touch()`
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3. If `PicoGraphics` constructor signature differs, update `init_display()`
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4. If `set_font()` font names differ, update font references
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5. If HTTPS doesn't work, switch `API_BASE` to `http://` or add SSL context
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<!-- SECTION:NOTES:END -->
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