Skip to main content

FTDI Buffer Fix on OS X


On some Macs, you may have noticed that the data coming from your board is very choppy.

This is a result of the FTDI virtual com port (VCP) driver's default settings for macOS. For more info on FTDI VCP drivers, see this forum thread and the FTDI VCP web page.

This document details how to edit the config data of the Info.plist file of your FTDI VCP driver, so that the choppiness is significantly reduced, and you are able to process the data in real-time, with minimal latency!

This tutorial has been verified to work with the following macOS versions:

  • 10.9
  • 10.10
  • 10.11
  • 10.13
  • 10.14
  • 10.15

Step 1: open Terminal#

To open Terminal, go to:


All of the lines of code you see below you will run from the Terminal command line. If you are unfamiliar with using Terminal, check out this Introduction to the Terminal in macOS Youtube tutorial.

!!! WARNING !!!

Be very careful when using the sudo rm command. It is used to remove files from your system. Never EVER enter the following command by itself, without specifying a filepath. That will wipe your hard drive.

If you are new to Terminal, it is best to simply copy and paste the lines of code below into your terminal window.

Step 2: Remove any existing FTDI drivers & reboot#

Remove the FTDI kernel extension (.kext) from your machine. You might not have it installed already. If you do not, skip this step.

sudo rm /System/Library/Extensions/FTDIUSBSerialDriver.kextsudo rm -rf /Library/Extensions/FTDIUSBSerialDriver.kext

After removing all existing FTDI drivers, reboot your computer.

Step 3: get the FTDI driver#

for macOS 10.9 to 10.11#

Download and install the FTDI Driver 2.2.18 for your processor from the FTDI VCP page. The latest FTDI VCP driver for macOS (version 2.3) does not work yet for this fix.

Here are the direct download links for 32-bit and 64-bit processors. Most likely you are working with 64-bit.

The downloaded .dmg comes with two installers in it. FTDIUSBSerialDriver_10_3 for OS X 10.3 and FTDIUSBSerialDriver_10_4_10_5_10_6_10_7 for the rest. You most likely need to install FTDIUSBSerialDriver_10_4_10_5_10_6_10_7.

for macOS 10.13 and 10.14#

Download and install the FTDI Driver 2.4.2 from the FTDI VCP page.

Step 4: enable dev mode#

Prior to making edits to the kext file, you must enable kext dev mode and disable signature verification. For OS X 10.10 or older, you just type:

sudo nvram boot-args="kext-dev-mode=1"

For 10.11 or newer, you need to reboot your computer and before booting, hold the Cmd-R key. This will get you into recovery mode. From Utilities, choose Terminal and type:

csrutil disable

You can then close the Terminal application and reboot your computer to normal mode. You can proceed with Step 6.

Step 5: reboot your computer#

After re-installing the FTDI driver and enabling kext dev mode, reboot your computer once more to ensure that everything has taken effect.

Step 6: plug in your dongle#

Plug in your dongle and ensure that the switch is set to GPIO6 (not RESET).


Step 7: unload the FTDI kernel extension#

sudo kextunload /System/Library/Extensions/FTDIUSBSerialDriver.kext

Step 8: make sure it's unloaded#

kextstat | grep FTDI

If everthing is good, nothing should print after running this command.

Step 9: open the Info.plist file:#

sudo emacs /System/Library/Extensions/FTDIUSBSerialDriver.kext/Contents/Info.plist


sudo vim /System/Library/Extensions/FTDIUSBSerialDriver.kext/Contents/Info.plist

Step 10: edit the config data#

Now add the new config data for the "FT X Series" as seen below. The "FT X Series" key is about 1/3 of the way through the Info.plist file and all of the keys are in alphabetical order. Scroll down to 'F'!

for macOS 10.9 to 10.11, using the driver 2.2.18#


<key>FT X Series</key><dict>       <key>CFBundleIdentifier</key>                                      <string>com.FTDI.driver.FTDIUSBSerialDriver</string>       <key>IOClass</key>       <string>FTDIUSBSerialDriver</string>       <key>IOProviderClass</key>       <string>IOUSBInterface</string>       <key>bConfigurationValue</key>       <integer>1</integer>       <key>bInterfaceNumber</key>       <integer>0</integer>       <key>bcdDevice</key>       <integer>4096</integer>       <key>idProduct</key>       <integer>24597</integer>       <key>idVendor</key>       <integer>1027</integer></dict>


<key>FT X Series</key><dict>        <key>CFBundleIdentifier</key>        <string>com.FTDI.driver.FTDIUSBSerialDriver</string>        <key>IOClass</key>        <string>FTDIUSBSerialDriver</string>        <key>IOProviderClass</key>        <string>IOUSBInterface</string>        <key>bConfigurationValue</key>        <integer>1</integer>        <key>bInterfaceNumber</key>        <integer>0</integer>        <key>bcdDevice</key>        <integer>4096</integer>        <key>idProduct</key>        <integer>24597</integer>        <key>idVendor</key>        <integer>1027</integer>        <key>ConfigData</key>        <dict>          <key>PortName</key>          <string>OpenBCI</string>          <key>InBufferSize</key>          <integer>64</integer>        </dict></dict>

Note: We also rename the port name to OpenBCI because it's easier to spot if the board is connected or not.

for macOS 10.13 and 10.14, using the driver 2.4.2#


<key>FT X Series</key><dict>  <key>CFBundleIdentifier</key>  <string>com.FTDI.driver.FTDIUSBSerialDriver</string>  <key>IOClass</key>  <string>FTDIUSBSerialDriver</string>  <key>IOProviderClass</key>  <string>IOUSBInterface</string>  <key>bConfigurationValue</key>  <integer>1</integer>  <key>bInterfaceNumber</key>  <integer>0</integer>  <key>bcdDevice</key>  <integer>4096</integer>  <key>idProduct</key>  <integer>24597</integer>  <key>idVendor</key>  <integer>1027</integer></dict>


<key>FT X Series</key><dict>  <key>CFBundleIdentifier</key>  <string>com.FTDI.driver.FTDIUSBSerialDriver</string>  <key>IOClass</key>  <string>FTDIUSBSerialDriver</string>  <key>IOProviderClass</key>  <string>IOUSBInterface</string>  <key>bConfigurationValue</key>  <integer>1</integer>  <key>bInterfaceNumber</key>  <integer>0</integer>  <key>bcdDevice</key>  <integer>4096</integer>  <key>idProduct</key>  <integer>24597</integer>  <key>idVendor</key>  <integer>1027</integer>  <key>ConfigData</key>  <dict>    <key>InBufferSize</key>    <integer>128</integer>    <key>LatencyTimer</key>    <integer>24</integer>  </dict></dict>

Step 11: save & close#

In emacs:

To save: [CTRL] + x followed by [CTRL] + s

To close emacs: [CTRL] + x followed by [CTRL] + c

In vim:

Hit the [esc] key to go into command mode. Then type :wq to save and quit.

Step 12: reload the kernel extension#

sudo kextload /System/Library/Extensions/FTDIUSBSerialDriver.kext

Step 13: make sure it's loaded#

kextstat | grep FTDI

You should get a response that looks something like this:

  145    0 0xffffff7f82dce000 0x8000     0x8000     com.FTDI.driver.FTDIUSBSerialDriver (2.2.18) <118 37 5 4 3 1>

Step 14: enjoy smoother streaming#

Open the OpenBCI Processing GUI (or other software), connect to your device, and begin streaming the data.

Helpful Resources#