If you're trying to connect to an Arduino, Pycom, Espressif or any other type of development board, you may notice it is not appearing when you connect it to your computer. The common issue is that you don't have the necessary drivers installed. Luckily this is pretty straight forward.
Click here to go to the Silicon Labs download page. Scroll down the list until you come to the Download for Macintosh OSX (v5) section. Here, click on the Mac OS X link to download the appropriate version for your machine.
Unzip the download and run the file
SiLabsUSBDriverDisk 3.dmg. Click Agree, then the following window will be opened.
Continue through the various steps in the installer. Once it's complete, you may need to reboot your computer.
Now your development board should be appearing when you connect it via USB. To check this, open a Terminal window and run the command
ls /dev/cu.* and see if it appears on your list of devices.