Added bugfix to prevent access errors on newly exported pin control files

examples/bitmap.php

@@ -33,4 +33,12 @@ for($n = 1; $n < 16; $n++) {
 	usleep(500000);
 }
 
+for($m = 0; $m < 20; $m++) {
+foreach(array(0, 0, 12, 14, 15, 7, 3, 1, 0) as $n) {
+	$par->write($n);
+	usleep(100000);
+}
+}
+
+
 $par->write(0);

lib/GpioPin.php

@@ -155,12 +155,19 @@ class GpioPin
         } else {
             $path = "/sys/class/gpio/{$file}";
         }
-        if (!is_writable($path)) {
+        if (!file_exists($path)) {
-            throw new HardwareException("Sysfs file {$path} not writable");
+            throw new HardwareException("Sysfs file {$path} does not exist");
         }
-        $f = fopen($path,"w+");
+
+        $ts = microtime(true);
+        while ((!is_writable($path)) && (microtime(true) < $ts+1)) {
+        	usleep(10000);
+        }
+
+        $f = @fopen($path,"c");
         if (!is_resource($f)) {
-            throw new HardwareException("Unable to write to sysfs file {$path}");
+        	$err = error_get_last();
+            throw new HardwareException("Unable to write to sysfs file {$path}: ".$err['message']);
         }
         fwrite($f,$value);
         fclose($f);