1. workaround to avoid uv__finish_close fatal error

2. set `power` and `ground` to null in driver.json

README.md

@@ -44,6 +44,8 @@ picture.on('end', function () {
  // ...
 });
 ```
+## FAQ
+If your get error message `Cannot find USB camera`, please confirm your camera has been pluged, and power down the ruff board and then power on it agagin.
 
 ## API References
 

driver.json

@@ -1,5 +1,7 @@
 {
     "models": [
         "uvc-01"
-    ]
+    ],
+    "power": null,
+    "ground": null
 }

package.json

@@ -14,7 +14,9 @@
   "homepage": "https://github.com/ruff-drivers/ruff-v1-usb-camera",
   "keywords": [
     "ruff",
-    "driver"
+    "driver",
+    "USB camera",
+    "UVC"
   ],
   "main": "src/index.js",
   "device-typings": "typings/device.d.ts",

src/camera.js

@@ -111,8 +111,12 @@ Camera.prototype._grabInit = function (callback) {
             });
         }
     ], function (error) {
+        if (error) {
+            callback && callback(error);
+            return;
+        }
         that._readPoll = new Poll(that._fifoFd);
-        callback && callback(error);
+        callback && callback();
     });
 };
 
@@ -132,6 +136,8 @@ Camera.prototype._grab = function (option, picture, callback) {
             var length = fs.readSync(that._fifoFd, buffer, 0, CHUNK_SIZE, -1);
             if (length === 0) {
                 that._readPoll.stop();
+                that._readPoll.close();
+                fs.closeSync(that._fifoFd);
                 picture.emit('end');
                 that._readCleanup(callback);
                 return;
@@ -150,11 +156,7 @@ Camera.prototype._grabCleanup = function (callback) {
 
 Camera.prototype._readCleanup = function (callback) {
     this._readFinish = true;
-    async.series([
-        this._readPoll.close.bind(this._readPoll),
-        fs.close.bind(fs, this._fifoFd),
-        this._cleanup.bind(this, callback)
-    ]);
+    this._cleanup(callback);
 };
 
 Camera.prototype._cleanup = function (callback) {