user10837: I installed OS X El Capitan beta on my Macbook. Now my Nano-sized Chinese Arduino operating on CH340 chip reboots the laptop when USB is unplugged. While plugged, it works fine, I can upload sketches and send/receive data via Serial. 
I've tried reinstalling the CH340 driver and running the following command as per this solution and it didn't help:
sudo nvram boot-args="kext-dev-mode=1 rootless=0"

I appreciate any ideas...

user11086: The command you ran only disables driver signing verification, which means OSX stops blocking it. If it is crashing it is likely to be either a bug in OSX, or a bug in the driver. My guess is it is a bug in the driver and you'll probably have to wait until they release an updated version that is compatible with El Capitan.

user10837: It turns out I didn't have the latest Beta. I now updated to the latest and now my CH340-based Arduino doesn't get detected at all! Pretty much in line with everyone else complaining all over internet.

user13984: Check this video https://www.youtube.com/watch?v=0zuRukW7o0A

Reboot and press CMD+R immediately after reboot to enter in Recovery Mode
Open Terminal from Recovery mode
Run the command csrutil enable --without kext
Reboot
Install driver


user19717: There is a new signed driver for OS-X El Capitan and Yosemite. This is all you want.
http://kig.re/2014/12/31/how-to-use-arduino-nano-mini-pro-with-CH340G-on-mac-osx-yosemite.html

10837: <p>I installed OS X El Capitan beta on my Macbook. Now my Nano-sized Chinese Arduino operating on CH340 chip reboots the laptop when USB is unplugged. While plugged, it works fine, I can upload sketches and send/receive data via Serial. </p>

<p>I've tried reinstalling the CH340 driver and running the following command as per <a href="https://www.reddit.com/r/arduino/comments/3dfr2e/ch340g_arduinos_with_osx_el_capitan/" rel="nofollow">this solution</a> and it didn't help:</p>

<pre><code>sudo nvram boot-args="kext-dev-mode=1 rootless=0"
</code></pre>

<p>I appreciate any ideas...</p>
 11086: <p>The command you ran only disables driver signing verification, which means OSX stops blocking it. If it is crashing it is likely to be either a bug in OSX, or a bug in the driver. My guess is it is a bug in the driver and you'll probably have to wait until they release an updated version that is compatible with El Capitan.</p>
 10837: <p>It turns out I didn't have the latest Beta. I now updated to the latest and now my CH340-based Arduino doesn't get detected at all! Pretty much in line with everyone else complaining all over internet.</p>
 13984: <p>Check this video <a href="https://www.youtube.com/watch?v=0zuRukW7o0A" rel="nofollow">https://www.youtube.com/watch?v=0zuRukW7o0A</a></p>

<ul>
<li>Reboot and press CMD+R immediately after reboot to enter in Recovery Mode</li>
<li>Open Terminal from Recovery mode</li>
<li>Run the command csrutil enable --without kext</li>
<li>Reboot</li>
<li>Install driver</li>
</ul>
 19717: <p>There is a new signed driver for OS-X El Capitan and Yosemite. This is all you want.</p>

<p><a href="http://kig.re/2014/12/31/how-to-use-arduino-nano-mini-pro-with-CH340G-on-mac-osx-yosemite.html" rel="nofollow">http://kig.re/2014/12/31/how-to-use-arduino-nano-mini-pro-with-CH340G-on-mac-osx-yosemite.html</a></p>
