macOS 10.14.3 or earlier

If you are running macOS 10.14.3 or earlier, the RHR app may not be able to detect any serial devices.

Please download and install the Swift 5 Runtime Support from Apple, then restart the RHR desktop app.

⬇️ Download Swift 5 Runtime Support for Command Line Tools


Install the latest FTDI drivers

Download and install the latest official FTDI driver package. Then reboot your Mac.

⬇️ Download FTDI drivers v2.4.2 (latest as of August, 2020) for macOS 10.9 and above


Try a different USB port

If a USB serial device is unplugged while the RHR app is using it, that USB port is now effectively dead ☠️ until the Mac reboots. This is due to a bug in the official FTDI drivers.

Plug your device into a different USB port, or reboot your Mac.



When in doubt, reboot your Mac.


*Advanced Debugging*


Ensure the RHR serial adapter is working

Go to Finder → Applications → Utilities → Terminal, and paste in this exact command (it's long).

/Applications/ list

✅ If the result looks like this, it is working:


⚠️ If the result looks like this (no COM port names listed), then the adapter is working, but the device is not plugged in or is not being recognized. Reboot, or try another USB port.


❌ If the result says No such file or directory, you do not have the RHR app installed. Please download the RHR app and unzip it to your Applications folder. Installing the RHR desktop app

❌ If the result looks like anything else, especially if it says dyld: Library not loaded, then the background serial communication program is not working. Please install the Swift 5 runtime (see above), or contact RHR support with your exact version of macOS. Contact support

Ensure macOS is using the correct serial drivers

Go to Finder → Applications → Utilities → Terminal, and paste in this exact command. You will be prompted for your user account password.

sudo kextstat | grep Serial

✅ If the results contain com.FTDI.driver.FTDIUSBSerialDriver, it is working.

❌ If the results contain AppleUSBFTDI, then the wrong drivers are being used. Please ensure you have installed the FTDI drivers (above), or contact RHR support with your exact macOS version. Contact support