diff --git a/fhem/CHANGED b/fhem/CHANGED
index b3468b86c..055aded7b 100644
--- a/fhem/CHANGED
+++ b/fhem/CHANGED
@@ -7,6 +7,7 @@
   - feature: .gplot files renamed from type to content
   - bugfix:  FS20 on-for-timer error reporting only in the logfile
   - bugfix:  FHEM2FHEM should work with CUL again, after syntax change
+  - feature: CUL directio mode (No Device::SerialPort needed)
 
 - 2011-07-08 (5.1)
   - feature: smallscreen optimizations for iPhone
diff --git a/fhem/FHEM/00_CUL.pm b/fhem/FHEM/00_CUL.pm
index a0780b7cd..4eb3db872 100755
--- a/fhem/FHEM/00_CUL.pm
+++ b/fhem/FHEM/00_CUL.pm
@@ -106,7 +106,8 @@ CUL_Define($$)
   my @a = split("[ \t][ \t]*", $def);
 
   if(@a < 4 || @a > 5) {
-    my $msg = "wrong syntax: define <name> CUL devicename[\@baudrate] <FHTID>";
+    my $msg = "wrong syntax: define <name> CUL {none | devicename[\@baudrate] ".
+                        "| devicename\@directio | hostname:port} <FHTID>";
     Log 2, $msg;
     return $msg;
   }
@@ -949,6 +950,7 @@ CUL_SimpleWrite(@)
 
   $hash->{USBDev}->write($msg)    if($hash->{USBDev});
   syswrite($hash->{TCPDev}, $msg) if($hash->{TCPDev});
+  syswrite($hash->{DIODev}, $msg) if($hash->{DIODev});
 
   select(undef, undef, undef, 0.001);
 }
@@ -958,22 +960,21 @@ sub
 CUL_SimpleRead($)
 {
   my ($hash) = @_;
+  my ($buf, $res);
 
   if($hash->{USBDev}) {
-    my $buf = $hash->{USBDev}->input();
-    #Log 1, "Got $buf";
-    return $buf;
-  }
+    $buf = $hash->{USBDev}->input();
+
+  } elsif($hash->{DIODev}) {
+    $res = sysread($hash->{DIODev}, $buf, 256);
+    $buf = undef if(!defined($res));
+
+  } elsif($hash->{TCPDev}) {
+    $res = sysread($hash->{TCPDev}, $buf, 256);
+    $buf = undef if(!defined($res));
 
-  if($hash->{TCPDev}) {
-    my $buf;
-    if(!defined(sysread($hash->{TCPDev}, $buf, 256))) {
-      CUL_Disconnected($hash);
-      return undef;
-    }
-    return $buf;
   }
-  return undef;
+  return $buf;
 }
 
 ########################
@@ -994,6 +995,10 @@ CUL_CloseDev($)
     $hash->{USBDev}->close() ;
     delete($hash->{USBDev});
 
+  } elsif($hash->{DIODev}) {
+    close($hash->{DIODev});
+    delete($hash->{DIODev});
+
   }
   ($dev, undef) = split("@", $dev); # Remove the baudrate
   delete($selectlist{"$name.$dev"});
@@ -1044,6 +1049,27 @@ CUL_OpenDev($$)
     delete($readyfnlist{"$name.$dev"});
     $selectlist{"$name.$dev"} = $hash;
 
+  } elsif(lc($baudrate) eq "directio") {   # Without Device::SerialPort
+
+    if(!open($po, "+<$dev")) {
+      return undef if($reopen);
+      Log(3, "Can't open $dev: $!");
+      $readyfnlist{"$name.$dev"} = $hash;
+      $hash->{STATE} = "disconnected";
+      return "";
+    }
+
+    $hash->{DIODev} = $po;
+
+    if( $^O =~ /Win/ ) {
+      $readyfnlist{"$name.$dev"} = $hash;
+    } else {
+      $hash->{FD} = fileno($po);
+      delete($readyfnlist{"$name.$dev"});
+      $selectlist{"$name.$dev"} = $hash;
+    }
+
+
   } else {                              # USB/Serial device
 
 
diff --git a/fhem/docs/commandref.html b/fhem/docs/commandref.html
index c078e4f40..b67c3c848 100644
--- a/fhem/docs/commandref.html
+++ b/fhem/docs/commandref.html
@@ -2048,8 +2048,16 @@ A line ending with \ will be concatenated with the next one, so long lines
       following command:<ul>modprobe usbserial vendor=0x03eb
       product=0x204b</ul>In this case the device is most probably
       /dev/ttyUSB0.<br><br>
+
       You can also specify a baudrate if the device name contains the @
       character, e.g.: /dev/ttyACM0@38400<br><br>
+
+      If the baudrate is "directio" (e.g.: /dev/ttyACM0@directio), then the
+      perl module Device::SerialPort is not needed, and fhem opens the device
+      with simple file io. This might work if the operating system uses sane
+      defaults for the serial parameters, e.g. some Linux distributions and
+      OSX.  <br><br>
+
     </ul>
     Network-connected devices (CUN):<br><ul>
     &lt;device&gt; specifies the host:port of the device. E.g.
@@ -2547,16 +2555,16 @@ A line ending with \ will be concatenated with the next one, so long lines
          <li>day-temp &lt;tmp&gt;<br>
              night-temp &lt;tmp&gt;<br>
              Set the day or night temperature. Temp must be between 6 and 30
-             Centigrade, and precision is half a degree.
-         <li>tempListSat HH:MM temp 24:00 temp ...<br>
-             tempListSun HH:MM temp 24:00 temp ...<br>
-             tempListMon HH:MM temp 24:00 temp ...<br>
-             tempListTue HH:MM temp 24:00 temp ...<br>
-             tempListThu HH:MM temp 24:00 temp ...<br>
-             tempListWed HH:MM temp 24:00 temp ...<br>
-             tempListFri HH:MM temp 24:00 temp ...<br>
+             Celsius, and precision is half a degree.
+         <li>tempListSat HH:MM temp ... 24:00 temp<br>
+             tempListSun HH:MM temp ... 24:00 temp<br>
+             tempListMon HH:MM temp ... 24:00 temp<br>
+             tempListTue HH:MM temp ... 24:00 temp<br>
+             tempListThu HH:MM temp ... 24:00 temp<br>
+             tempListWed HH:MM temp ... 24:00 temp<br>
+             tempListFri HH:MM temp ... 24:00 temp<br>
              Specify a list of temperature intervals. Up to 24 intervals can be
-             spacified for each week day, the resolution is 10 Minutes. The
+             specified for each week day, the resolution is 10 Minutes. The
              last time spec must always be 24:00.<br>
              Example: set th tempListSat 06:00 19 23:00 22.5 24:00 19<br>
        </ul></li>
@@ -2567,11 +2575,11 @@ A line ending with \ will be concatenated with the next one, so long lines
        <ul>
          <li>raw &lt;data&gt; ...<br>
              Only needed for experimentation.
-             send a list of "raw" commands. The first command will be immediately
-             sent, the next one after the previous one is acked by the target.  The
-             length will be computed automatically, and the message counter will be
-             incremented if the first two charcters are ++.
-             Example (enable AES):<pre>
+             send a list of "raw" commands. The first command will be
+             immediately sent, the next one after the previous one is acked by
+             the target.  The length will be computed automatically, and the
+             message counter will be incremented if the first two charcters are
+             ++. Example (enable AES):<pre>
    set hm1 raw ++A001F100001234560105000000001\
                ++A001F10000123456010802010AF10B000C00\
                ++A001F1000012345601080801\