Add script.

usb/led_pwm.js

@@ -0,0 +1,44 @@
+#!/usr/bin/env node
+'use strict';
+
+var usb = require('usb');
+var util = require('./util');
+
+var vid = 0x16d3;
+var pid = 0x05ea;
+var LED_PWM_COMMAND_ID = 10;
+
+var device = usb.findByIds(vid, pid);
+device.open();
+
+var usbInterface = device.interface(0);
+
+// https://github.com/tessel/node-usb/issues/147
+// The function 'isKernelDriverActive' is not available on Windows and not even needed.
+if (process.platform !== 'win32' && usbInterface.isKernelDriverActive()) {
+    usbInterface.detachKernelDriver();
+}
+usbInterface.claim();
+
+var endpointIn = usbInterface.endpoints[0];
+var endpointOut = usbInterface.endpoints[1];
+
+var brightnessPercent = 0;
+
+setInterval(function() {
+    brightnessPercent = brightnessPercent ? 0 : 100
+    console.log('Sending ', brightnessPercent);
+    endpointOut.transfer(new Buffer([LED_PWM_COMMAND_ID, brightnessPercent]), function(err) {
+        if (err) {
+            console.error("USB error: %s", err);
+            process.exit(1);
+        }
+        endpointIn.transfer(64, function(err2, receivedBuffer) {
+            if (err2) {
+                console.error("USB error: %s", err2);
+                process.exit(2);
+            }
+            console.log('Received', util.bufferToString(receivedBuffer));
+        })
+    });
+}, 500)