Add README and QML usage guide for UI designers

1 files changed, 199 insertions, 0 deletions

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a396945
--- /dev/null
+++ b/README.md
@@ -0,0 +1,199 @@
+# BobinkQtOpcUa
+
+A C++ library that wraps [Qt OPC UA](https://doc.qt.io/qt-6/qtopcua-index.html) into simple QML components for Qt Quick applications. Hide OPC UA complexity behind a clean, declarative API.
+
+## Quick start
+
+### Prerequisites
+
+- CMake >= 3.16, Ninja
+- Qt 6.10.2+ (with `qt-cmake` in PATH)
+- OpenSSL development headers
+
+### Build
+
+```bash
+git clone --recurse-submodules https://github.com/user/BobinkQtOpcUa.git
+cd BobinkQtOpcUa
+
+qt-cmake -S . -B build -G Ninja
+qt-cmake --build build --parallel
+```
+
+The first configure automatically builds the bundled dependencies (open62541 and QtOpcUa) from git submodules under `deps/`. Subsequent builds skip this step.
+
+### Run the demo
+
+```bash
+./build/bin/BobinkDemo
+```
+
+The demo app discovers local OPC UA servers, connects with configurable authentication and security, and lets you monitor and write to nodes.
+
+## Usage
+
+Import the `Bobink` QML module:
+
+```qml
+import Bobink
+```
+
+### Connect to a server
+
+```qml
+Connections {
+    target: Bobink
+    function onConnectedChanged() {
+        console.log("Connected:", Bobink.connected)
+    }
+    function onConnectionError(message) {
+        console.log("Error:", message)
+    }
+    function onCertificateTrustRequested(certInfo) {
+        // Show certInfo to user, then call:
+        Bobink.acceptCertificate()  // or rejectCertificate()
+    }
+}
+
+Button {
+    text: "Connect"
+    onClicked: {
+        Bobink.serverUrl = "opc.tcp://localhost:4840"
+        Bobink.connectToServer()
+    }
+}
+```
+
+`connectToServer()` discovers endpoints and auto-selects the most secure one. If that fails, use `connectDirect()` with explicit security settings:
+
+```qml
+Bobink.connectDirect(Bobink.Basic256Sha256, Bobink.SignAndEncrypt)
+```
+
+### Authentication
+
+```qml
+OpcUaAuth {
+    id: auth
+    mode: OpcUaAuth.Anonymous  // or UserPass, Certificate
+    username: "user"
+    password: "pass"
+}
+
+// Set before connecting
+Bobink.auth = auth
+Bobink.connectToServer()
+```
+
+### Monitor and write nodes
+
+```qml
+OpcUaMonitoredNode {
+    id: tempNode
+    nodeId: "ns=2;s=Temperature"
+    monitored: true  // creates an OPC UA monitored item
+    publishingInterval: 500  // ms
+
+    onValueChanged: console.log("Temperature:", value)
+    onWriteCompleted: (success, message) => console.log(message)
+}
+
+// Display live value
+Text { text: "Temperature: " + tempNode.value }
+
+// Write a new value
+Button {
+    text: "Set to 25"
+    enabled: tempNode.writable
+    onClicked: tempNode.writeValue(25)
+}
+```
+
+Type coercion is automatic -- QML values are converted to the node's OPC UA data type. For arrays, pass a comma-separated string: `writeValue("1, 2, 3")`.
+
+Write to specific array elements with index range syntax:
+
+```qml
+tempNode.writeValueAtRange("42", "0")       // first element
+tempNode.writeValueAtRange("1, 2, 3", "0:2") // elements 0-2
+```
+
+### Node metadata
+
+Each `OpcUaMonitoredNode` exposes an `info` property with metadata read once on setup:
+
+```qml
+Text { text: node.info.displayName }
+Text { text: node.info.dataType }
+Text { text: node.info.description }
+// Also: nodeClass, valueRank, arrayDimensions, accessLevel,
+//        status, sourceTimestamp, serverTimestamp
+```
+
+### Server discovery
+
+```qml
+Component.onCompleted: {
+    Bobink.discoveryUrl = "opc.tcp://localhost:4840"
+    Bobink.startDiscovery()
+}
+
+ListView {
+    model: Bobink.servers
+    delegate: Text {
+        text: modelData.serverName
+        // Also available: modelData.applicationUri, modelData.discoveryUrls
+    }
+}
+```
+
+### PKI
+
+Client certificates are auto-detected from the default PKI directory (`<AppDataLocation>/pki`). To configure manually:
+
+```qml
+Bobink.pkiDir = "/path/to/pki"
+Bobink.certFile = "/path/to/cert.der"
+Bobink.keyFile = "/path/to/key.pem"
+Bobink.applyPki()
+```
+
+## Use as a git submodule
+
+BobinkQtOpcUa can be added to your project as a git submodule:
+
+```bash
+git submodule add https://github.com/user/BobinkQtOpcUa.git deps/bobink
+git submodule update --init --recursive
+```
+
+```cmake
+# CMakeLists.txt
+add_subdirectory(deps/bobink)
+
+# Link against the library and its QML plugin
+target_link_libraries(YourApp PRIVATE BobinkQtOpcUaplugin)
+
+# Set RPATH so the open62541 backend plugin loads at runtime
+set(CMAKE_BUILD_RPATH "${OPEN62541_INSTALL_DIR}/lib"
+                      "${QTOPCUA_INSTALL_DIR}/lib")
+
+# Tell Qt where to find the OPC UA backend plugin
+target_compile_definitions(YourApp PRIVATE
+    QTOPCUA_PLUGIN_PATH="${QTOPCUA_INSTALL_DIR}/plugins")
+```
+
+## Project structure
+
+```
+src/
+  OpcUaClient.h/.cpp         Bobink singleton: connection, discovery, PKI
+  OpcUaMonitoredNode.h/.cpp   Node monitoring, reading, writing
+  OpcUaAuth.h/.cpp            Authentication configuration
+demo/
+  Main.qml                    Connection UI demo
+  NodePage.qml                Node interaction demo
+deps/
+  open62541/                   C OPC UA stack (submodule)
+  qtopcua/                     Qt OPC UA module (submodule)
+```