user31071: I have used by Arduino countless times over the past few years and only after installing an update to Mac OS Sierra did the device stop showing up under the Serial Ports. Now only tty-bluetooth shows up no others. I have looked a countless threads where people suggest installing drivers or uninstalling drivers or rebooting. I have tried everything but still no device shows up. 
I switched to my Windows partition using Bootcamp and lo and behold it works perfectly there but not in Mac OS. I would still like to use Mac OS to programme my Arduino. If anyone has any suggestions I would be very grateful! 

user30002: Is it an original Nano or a clone?
The original Nano uses FTDI's FT232 ship, whereas clones use the CG340 USB-to-TTL chip. The former works fine straight away Mac OS Sierra, whereas the latter needs a driver.
The CG340 driver doesn't work under Mac OS Sierra. Fortunately, someone patched the driver and made it available at GitHub. There you'll also find some troubleshooting instructions that can help (hopefully).
From Adrian Mihalko's repository at GitHub:

ch340g-ch34g-ch34x-mac-os-x-driver
Latest macOS Sierra-compatible driver for devices using the CH340G, CH34G or CH34X chipset. This chipset is used in several Arduino-clones.
Introduction
Version 1.3 (2016-09-27) of the OEM driver for the CH34x chipset currently causes a kernel panic (a.k.a. crash) when installed on macOS Sierra. To resolve this issue, please download and install the driver in this repo.
Installation

Remove the old driver by issuing one of the following commands (depending on your installation):


sudo rm -rf /System/Library/Extensions/usb.kext
sudo rm -rf /Library/Extensions/usbserial.kext

Restart your Mac.
Double-click on the CH34x_Install_V1.3.pkg file.
Restart your Mac.
Plug in your device. It should now be listed under the /dev directory. Examples:


/dev/cu.wchusbserial1410
/dev/cu.wchusbserial1420


Troubleshooting
If, and only if, the device is not recognized after the installation (or you cannot install the driver), please disable System Integrity Protection:

Reboot your Mac into Recovery Mode by restarting your computer and holding down Command+R until the Apple logo appears on screen.
Open the Terminal (Applications > Utilities > Terminal).
In the Terminal window, type in csrutil enable --without kext (or to fully disable: csrutil disable) and press Enter.
Restart your Mac.

Please share this page!
Regards,
Adrian Mihalko

31071: <p>I have used by Arduino countless times over the past few years and only after installing an update to Mac OS Sierra did the device stop showing up under the Serial Ports. Now only tty-bluetooth shows up no others. I have looked a countless threads where people suggest installing drivers or uninstalling drivers or rebooting. I have tried everything but still no device shows up. </p>

<p>I switched to my Windows partition using Bootcamp and lo and behold it works perfectly there but not in Mac OS. I would still like to use Mac OS to programme my Arduino. If anyone has any suggestions I would be very grateful! </p>
 30002: <p>Is it an original Nano or a clone?</p>

<p>The original Nano uses FTDI's FT232 ship, whereas clones use the CG340 USB-to-TTL chip. The former works fine straight away Mac OS Sierra, whereas the latter needs a driver.</p>

<p>The CG340 driver doesn't work under Mac OS Sierra. Fortunately, someone patched the driver and made it <a href="https://github.com/adrianmihalko/ch340g-ch34g-ch34x-mac-os-x-driver" rel="noreferrer">available at GitHub</a>. There you'll also find some troubleshooting instructions that can help (hopefully).</p>

<p>From Adrian Mihalko's repository at GitHub:</p>

<hr>

<h1>ch340g-ch34g-ch34x-mac-os-x-driver</h1>

<p>Latest <strong>macOS Sierra</strong>-compatible driver for devices using the CH340G, CH34G or CH34X chipset. This chipset is used in several Arduino-clones.</p>

<h2>Introduction</h2>

<p>Version 1.3 (2016-09-27) of the <a href="http://www.wch.cn/download/CH341SER_MAC_ZIP.html" rel="noreferrer">OEM driver</a> for the CH34x chipset currently causes a kernel panic (a.k.a. <em>crash</em>) when installed on <strong>macOS Sierra.</strong> To resolve this issue, please download and install the driver in this repo.</p>

<h2>Installation</h2>

<ul>
<li>Remove the old driver by issuing one of the following commands (depending on your installation):

<ul>
<li><code>sudo rm -rf /System/Library/Extensions/usb.kext</code></li>
<li><code>sudo rm -rf /Library/Extensions/usbserial.kext</code></li>
</ul></li>
<li>Restart your Mac.</li>
<li>Double-click on the <code>CH34x_Install_V1.3.pkg</code> file.</li>
<li>Restart your Mac.</li>
<li>Plug in your device. It should now be listed under the <code>/dev</code> directory. Examples:

<ul>
<li><code>/dev/cu.wchusbserial1410</code></li>
<li><code>/dev/cu.wchusbserial1420</code></li>
</ul></li>
</ul>

<h2>Troubleshooting</h2>

<p>If, and only if, the device is not recognized after the installation (or you cannot install the driver), please disable <em>System Integrity Protection</em>:</p>

<ul>
<li>Reboot your Mac into <em>Recovery Mode</em> by restarting your computer and holding down <code>Command+R</code> until the Apple logo appears on screen.</li>
<li>Open the Terminal (Applications > Utilities > Terminal).</li>
<li>In the Terminal window, type in <code>csrutil enable --without kext</code> (or to fully disable: <code>csrutil disable</code>) and press Enter.</li>
<li>Restart your Mac.</li>
</ul>

<p>Please share this page!</p>

<p>Regards,
Adrian Mihalko</p>
