OpenBeken HTTP Channel Value Read: Ch<n>, GetChannel, JSON API, Firmware 1.17.x
User question
show channel value via http
Artificial Intelligence Response
Direct answer to the question
- Use the device’s HTTP command endpoint and request the channel by name:
- Single channel (index n): http:///cm?cmnd=Ch
- Alternative: http:///cm?cmnd=GetChannel%20
- Typical response: a tiny JSON object with the current value, for example: {"Ch5":42}
- Notes:
- Channel indices are 0-based in OpenBeken (Ch0 is valid). Verify your target index.
- Channel values are floating-point variables; they may represent binary, PWM, sensor readings, etc.
Key points
- Fastest: /cm?cmnd=Ch (returns only what you asked for).
- If you need a snapshot of many values, use the JSON state endpoint available in your build (see details below).
- URL-encode spaces (GetChannel%20).
- Secure the endpoint if exposed beyond your LAN.
Detailed problem analysis
- Channel abstraction: In OpenBeken (OBK), “channels” are general-purpose variables bound to relays, PWM, sensors, or pure logic. Internally they are stored as floating-point numbers. A relay channel typically returns 0/1; PWM/dimmer may return a scaled integer or float (commonly 0–100 or 0–255 depending on template/config); sensors return real-world values (e.g., temperature).
- HTTP command interface:
- Endpoint: /cm?cmnd= (Tasmota-style).
- Read methods:
- Ch: Direct, succinct; returns the value mapped to channel n, e.g., /cm?cmnd=Ch0 → {"Ch0":1}
- GetChannel : Equivalent read with an explicit verb; requires URL-encoded space, e.g., /cm?cmnd=GetChannel%200
- Response format: OBK’s /cm endpoint responds with compact JSON. This is simple to parse in scripts, HA REST sensors, Node-RED, or custom apps.
- All-channels/state JSON:
- Newer OBK builds provide JSON snapshots (exact endpoint name can vary by version). Commonly, /json?get=all (or a variant like /json?get=channels) returns a JSON object where “channels” holds an index→value map. Prefer single-channel reads for low overhead; use a snapshot only when you need many points at once.
- Indexing and naming:
- Indexing is 0-based for HTTP commands (Ch0, Ch1, …).
- Some UI pages may present user-facing labels or 1-based numbering; always match the HTTP command’s 0-based index.
- Robustness and latency:
- A single GET completes in a few milliseconds on a LAN. For polling dashboards, a 1–2 s interval is typically sufficient. For faster updates, consider event-driven approaches (WebSocket/SSE if enabled on your build).
Current information and trends
- Reliable, minimal-overhead reads use Ch and GetChannel .
- Channels being floating-point variables enables flexible math/logic on-device; many users mix binary and analog uses in the same mechanism.
- Recent 1.17.x+ builds strengthened the JSON API surface; if you maintain tooling, code defensively (feature-detect the JSON endpoint, or fall back to single-channel reads).
Supporting explanations and details
- Example with curl:
- Plain JavaScript fetch:
- fetch('/cm?cmnd=Ch3').then(r=>r.json()).then(j=>console.log(j.Ch3));
- Python (requests):
- Reading multiple channels efficiently:
- If your firmware exposes /json?get=all or /json?get=channels, fetch once and read json["channels"]["0"], json["channels"]["1"], etc.
- Otherwise batch multiple single-channel requests in parallel from your client (keep-alive on).
- Typical value ranges:
- Relay: 0/1
- PWM/Dimmer: 0–100 or 0–255 (check your template and DimmerScale configuration)
- Sensors: floating-point in engineering units (°C, %, V, etc.)
Ethical and legal aspects
- Do not expose the device’s HTTP interface directly to the public Internet.
- If remote access is required, place the device behind a VPN or a reverse proxy that provides TLS and authentication.
- Observe local regulations for networked devices in safety-critical applications (e.g., lighting in public venues, HVAC control).
Practical guidelines
- Quick checklist:
- Confirm device IP and that the web server is enabled.
- Verify channel index (remember: 0-based).
- Test with /cm?cmnd=Ch; confirm JSON output.
- For dashboards, parse the JSON and cache results to avoid excessive polling.
- Home Assistant RESTful Sensor example:
- Node-RED:
- Use http request node → JSON parse → change node to msg.payload = msg.payload.Ch3.
Potential challenges and how to overcome them
- Getting 0 for “unused” channels: verify your template/channel mapping and that the source is producing data.
- Mixed indexing confusion: confirm with Ch0; if it returns a value, your build is 0-based (standard).
- Space in command: always URL-encode (GetChannel%201).
Possible disclaimers or additional notes
- JSON API endpoint names may vary slightly across OBK builds; if /json?get=all is not present, rely on Ch/GetChannel .
- Some third-party integrations assume integer-only channels; OBK channels are floats—cast/round as needed in your client.
Suggestions for further research
- Review OpenBeken documentation for your specific firmware version’s JSON endpoints and any changes introduced in 1.17.x and later.
- Explore event-driven options (WebSocket/SSE) if your build exposes them to reduce polling overhead.
- Look up community threads on channel math, SetChannel, and virtual channels for on-device preprocessing.
Brief summary
- To show a channel value via HTTP on OpenBeken, call /cm?cmnd=Ch or /cm?cmnd=GetChannel%20. The response is compact JSON with the current value. Channels are 0-based and float-typed. For many values at once, use the JSON state endpoint if available; otherwise poll single channels at modest intervals and secure access if used beyond your LAN.
Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.
