diff --git a/src-tauri/src/commands.rs b/src-tauri/src/commands.rs
index 089e9bb..cde492b 100644
--- a/src-tauri/src/commands.rs
+++ b/src-tauri/src/commands.rs
@@ -386,14 +386,24 @@ pub async fn read_tiff_preview_png(path: String) -> Result<String, String> {
 pub struct ChartreadConfig {
     pub basename: String,
     pub cwd: String,
+    pub port: Option<String>,
 }
 
 pub fn build_chartread_args(config: &ChartreadConfig) -> Vec<String> {
-    vec![
+    let mut args = vec![
         "-v".to_string(),
         "-u".to_string(),
-        config.basename.clone(),
-    ]
+    ];
+
+    if let Some(ref port) = config.port {
+        if !port.trim().is_empty() {
+            args.push("-c".to_string());
+            args.push(port.trim().to_string());
+        }
+    }
+
+    args.push(config.basename.clone());
+    args
 }
 
 #[tauri::command]
@@ -699,11 +709,23 @@ mod tests {
         let config = ChartreadConfig {
             basename: "my_profile".to_string(),
             cwd: "/home/user".to_string(),
+            port: None,
         };
         let args = build_chartread_args(&config);
         assert_eq!(args, vec!["-v", "-u", "my_profile"]);
     }
 
+    #[test]
+    fn test_build_chartread_args_with_port() {
+        let config = ChartreadConfig {
+            basename: "my_profile".to_string(),
+            cwd: "/home/user".to_string(),
+            port: Some("1".to_string()),
+        };
+        let args = build_chartread_args(&config);
+        assert_eq!(args, vec!["-v", "-u", "-c", "1", "my_profile"]);
+    }
+
     #[test]
     fn test_build_colprof_args() {
         let config = ColprofConfig {
diff --git a/src/index.html b/src/index.html
index 4af00bd..104de42 100644
--- a/src/index.html
+++ b/src/index.html
@@ -249,6 +249,19 @@
           <h2>Measure Target</h2>
           <p>Read the printed target patches with your spectrophotometer.</p>
 
+          <!-- Instrument & Hardware Port Selector -->
+          <div class="form-container" style="margin-bottom: 16px;">
+            <div class="form-group">
+              <label for="chartreadInstrumentSelect">Instrument / Hardware Port</label>
+              <div class="input-row" style="display: flex; gap: 8px; align-items: center;">
+                <select id="chartreadInstrumentSelect" style="flex: 1;">
+                  <option value="">Auto-Detect (First Available Instrument)</option>
+                </select>
+                <button type="button" class="secondary" id="btnDetectInstruments" title="Detect connected instruments via instlist">↻ Detect</button>
+              </div>
+            </div>
+          </div>
+
           <!-- State & Prompt Area -->
           <div class="chartread-status">
             <div class="status-label">State: <span id="chartreadState">IDLE</span></div>
@@ -485,4 +498,4 @@
       </div>
     </dialog>
   </body>
-</html>
+</html>
\ No newline at end of file
diff --git a/src/js/chartread.js b/src/js/chartread.js
index 9b78b92..3020dd4 100644
--- a/src/js/chartread.js
+++ b/src/js/chartread.js
@@ -36,11 +36,70 @@ export function initChartread() {
   const btnRetry = document.getElementById("btnRetry");
   const btnSkip = document.getElementById("btnSkip");
   const btnCancel = document.getElementById("btnCancel");
+  const btnDetectInstruments = document.getElementById("btnDetectInstruments");
+  const instrumentSelect = document.getElementById("chartreadInstrumentSelect");
   const promptText = document.getElementById("chartreadPrompt");
   const stateLabel = document.getElementById("chartreadState");
   const logContainer = document.getElementById("chartreadLogContainer");
   const logPre = document.getElementById("chartreadLog");
 
+  // Instrument detection logic
+  if (btnDetectInstruments && instrumentSelect) {
+    btnDetectInstruments.addEventListener("click", async () => {
+      btnDetectInstruments.disabled = true;
+      btnDetectInstruments.textContent = "Detecting...";
+      setPrompt("Querying connected spectrophotometers and colorimeters via instlist...");
+
+      const detected = [];
+
+      try {
+        const unlistenStdout = await listen("process:stdout", (event) => {
+          if (event.payload.id !== "instlist" || !event.payload.line) return;
+          const line = event.payload.line.trim();
+
+          // Matches Argyll instlist output e.g. "1: 'i1Pro' on 'USB'" or "1: 'ColorMunki'" or "1 = 'i1Display'"
+          const match = line.match(/^(\d+)[\s:=]+'?([^'\n]+)'?(?:\s+on\s+'?([^'\n]+)'?)?/i);
+          if (match) {
+            const index = match[1];
+            const name = match[2].trim();
+            const port = match[3] ? match[3].trim() : "";
+            detected.push({ index, name, port });
+          }
+        });
+
+        const unlistenExit = await listen("process:exit", (event) => {
+          if (event.payload.id !== "instlist") return;
+          unlistenStdout();
+          unlistenExit();
+          btnDetectInstruments.disabled = false;
+          btnDetectInstruments.textContent = "↻ Detect";
+
+          instrumentSelect.innerHTML = `<option value="">Auto-Detect (First Available Instrument)</option>`;
+
+          if (detected.length > 0) {
+            detected.forEach((inst) => {
+              const opt = document.createElement("option");
+              opt.value = inst.index;
+              opt.textContent = `${inst.index}: ${inst.name} ${inst.port ? `(${inst.port})` : ""}`;
+              instrumentSelect.appendChild(opt);
+            });
+            instrumentSelect.value = detected[0].index;
+            setPrompt(`Found ${detected.length} instrument(s): ${detected.map(d => d.name).join(", ")}`);
+          } else {
+            setPrompt("No instruments found via instlist. Ensure USB cable is plugged in.");
+          }
+        });
+
+        await invoke("detect_instruments");
+      } catch (err) {
+        console.error("detect_instruments error:", err);
+        btnDetectInstruments.disabled = false;
+        btnDetectInstruments.textContent = "↻ Detect";
+        setPrompt(`Instrument detection error: ${err}`);
+      }
+    });
+  }
+
   function setState(newState) {
     currentState = newState;
     if (stateLabel) stateLabel.textContent = newState;
@@ -103,9 +162,12 @@ export function initChartread() {
       setState(STATE.CALIBRATING);
       setPrompt("Starting chartread... waiting for instrument calibration prompt.");
 
+      const selectedPort = instrumentSelect && instrumentSelect.value ? instrumentSelect.value : null;
+
       const config = {
         basename: basename,
         cwd: cwd,
+        port: selectedPort,
       };
 
       currentProcessId = `chartread_${basename}`;