> ## Documentation Index > Fetch the complete documentation index at: https://docs.closient.com/llms.txt > Use this file to discover all available pages before exploring further. # TRMNL display poll > Called by TRMNL firmware on every refresh cycle to decide what to paint. The server returns an ``image_url`` pointing to the device's next PNG plus a ``refresh_rate`` telling firmware when to poll again. Phase 1 always returns the current ``image_url`` — image generation is synchronous and per-request. A future phase will switch to S3-backed pre-rendered images so many devices can share a single render. **Auth:** ``Access-Token`` header (the opaque per-device token issued by ``/api/setup/``). * ``200`` — image ready. * ``401`` — missing, unknown, or disabled ``Access-Token``. ## OpenAPI ````yaml /openapi/openapi-byos.json get /byos/api/display openapi: 3.1.0 info: title: BYOS API version: 1.0.0 description: > Closient's TRMNL-compatible **Bring Your Own Server** endpoints. Powers e-ink analytics displays — devices poll ``/api/setup/`` on first boot, then ``/api/display`` on a schedule to fetch the image they should paint. The wire protocol matches TRMNL's BYOS contract verbatim so off-the-shelf reTerminal firmware works without modification. ## Authentication All endpoints require an API key passed via the `X-API-Key` HTTP header, unless otherwise noted. ``` X-API-Key: csb__ ``` Generate API keys in **Settings > API Keys** in your dashboard, or via the Account API. Session-based (cookie) authentication is also accepted for browser-based access. ## Rate Limits | Tier | Requests / minute | Requests / day | |-------------|-------------------|----------------| | Default | 300 | 10,000 | | Custom | Contact us | Contact us | Rate-limit headers are included on every response so callers can self-throttle without hitting our 429s ("informed governor"): - `RateLimit-Policy` — every active window, e.g. `300;w=60, 10000;w=86400` - `RateLimit-Limit` — quota for the **most-restrictive** currently-active window - `RateLimit-Remaining` — requests left in that window - `RateLimit-Reset` — seconds until that window resets (relative; clock-skew safe) Legacy `X-RateLimit-*` aliases are also emitted for back-compat. `X-RateLimit-Reset` keeps the absolute Unix-timestamp shape to avoid breaking existing consumers. When rate-limited, you receive `429 Too Many Requests` with a `retry_after_seconds` field in the error envelope and a `Retry-After` header. ## Pagination List endpoints return paginated results in this envelope: ```json { "data": [...], "pagination": { "page": 1, "page_size": 25, "total_count": 342, "total_pages": 14, "has_next": true, "has_previous": false } } ``` Use `?page=2&page_size=50` query parameters. Maximum page size is 100. ## Error Responses All errors conform to [RFC 9457 Problem Details](https://www.rfc-editor.org/rfc/rfc9457) with `Content-Type: application/problem+json`: ```json { "type": "https://closient.com/docs/errors/not_found", "title": "Not Found", "status": 404, "detail": "The requested resource was not found.", "error_code": "not_found", "retryable": false, "timestamp": "2026-03-31T12:00:00+00:00" } ``` Common error codes: `unauthorized` (401), `forbidden` (403), `not_found` (404), `validation_error` (422), `rate_limited` (429), `internal_error` (500). termsOfService: https://www.closient.com/terms/ servers: - url: https://www.closient.com security: [] externalDocs: description: Closient Documentation url: https://docs.closient.com paths: /byos/api/display: get: tags: - byos-trmnl summary: TRMNL display poll description: >- Called by TRMNL firmware on every refresh cycle to decide what to paint. The server returns an ``image_url`` pointing to the device's next PNG plus a ``refresh_rate`` telling firmware when to poll again. Phase 1 always returns the current ``image_url`` — image generation is synchronous and per-request. A future phase will switch to S3-backed pre-rendered images so many devices can share a single render. **Auth:** ``Access-Token`` header (the opaque per-device token issued by ``/api/setup/``). * ``200`` — image ready. * ``401`` — missing, unknown, or disabled ``Access-Token``. operationId: apps_boards_api_trmnl_trmnl_display parameters: [] responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/DisplayOut' '400': description: Bad Request content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '401': description: Unauthorized content: application/problem+json: schema: additionalProperties: true title: Response type: object '403': description: Forbidden content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '404': description: Not Found content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '405': description: Method Not Allowed content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' '429': description: Too Many Requests content: application/problem+json: schema: $ref: '#/components/schemas/ErrorOut' security: - TRMNLDeviceAuth: [] components: schemas: DisplayOut: description: |- Response to ``GET /api/display``. Tells the device what to draw next, how long to wait before checking again, and (optionally) whether to take firmware action. examples: - device_status: claimed filename: closient-A1B2C3-3f9a2c1d8e.png firmware_url: '' image_url: https://www.closient.com/byos/devices/A1B2C3/image.png refresh_rate: 900 reset_firmware: false status: 0 update_firmware: false properties: status: default: 0 description: >- TRMNL display status code. ``0`` means "image ready"; non-zero values are reserved for future TRMNL extensions. title: Status type: integer image_url: description: >- Absolute URL the device should fetch and paint. Currently a Django view that streams the rendered 2-bit PNG. title: Image Url type: string filename: description: >- Suggested filename for the device's local cache (the device de-dupes by this name). title: Filename type: string refresh_rate: description: >- Seconds the device should wait before polling ``/api/display`` again. Bounded to [60s, 24h]. maximum: 86400 minimum: 60 title: Refresh Rate type: integer reset_firmware: default: false description: >- Whether the device should reset to first-boot state on next reboot. Unused in Phase 1. title: Reset Firmware type: boolean update_firmware: default: false description: >- Whether the device should fetch new firmware. Unused in Phase 1 — Closient does not host firmware images. title: Update Firmware type: boolean firmware_url: default: '' description: >- URL of new firmware to fetch when ``update_firmware`` is true. Empty in Phase 1. title: Firmware Url type: string device_status: $ref: '#/components/schemas/BYOSDeviceStatusEnum' description: >- Closient-side lifecycle state of this device. Non-standard extension to the TRMNL response — TRMNL firmware ignores it; dashboards consume it for status badges. required: - image_url - filename - refresh_rate - device_status title: DisplayOut type: object ErrorOut: title: ErrorOut type: object description: RFC 9457 Problem Details error body. properties: type: type: string format: uri title: type: string status: type: integer detail: type: string error_code: type: string retryable: type: boolean timestamp: type: string format: date-time required: - type - title - status - detail examples: - type: https://closient.com/docs/errors/not_found title: Not Found status: 404 detail: The requested resource was not found. error_code: not_found retryable: false timestamp: '2026-03-31T12:00:00+00:00' BYOSDeviceStatusEnum: description: |- Lifecycle state of a :class:`apps.boards.models.BYOSDevice`. State machine: * ``unclaimed`` — device has called ``/api/setup/`` but is not yet linked to a Closient :class:`Organization`. Renders the BYOS fallback "register me" image. * ``claimed`` — device is linked to an organization and renders the org-typed dashboard. * ``disabled`` — device is administratively disabled and rejected at auth time. Used to retire lost/stolen panels without deleting the row (so historical logs survive). enum: - unclaimed - claimed - disabled title: BYOSDeviceStatusEnum type: string securitySchemes: TRMNLDeviceAuth: type: apiKey in: header name: Access-Token ````