You can only access USB Serial Adapters using pyserial (i.e., USB RS-232 dongles). If you want generic USB access you should be looking into 'libusb'. If it is RS-232 you are trying to access through USB then you should look for a file in /dev starting with cu.usb. (/dev/cu.usbserial-181 for example). The StarTech.com ICUSB232 1ft USB to DB9 RS232 Serial Adapter Cable lets you connect DB9 RS232 serial devices to your Mac or PC laptop or desktop computer through a USB port, as though the computer offered an onboard DB9M connector.
Information about these and other types of Mac ports is in the specifications for your Mac: Choose Apple menu > About This Mac, click Support, then click Specifications. Or check your Mac user guide.
Thunderbolt 3
Use Thunderbolt 3 with displays and other devices that connect using either a Thunderbolt 3 cable or USB-C cable. You can also connect a USB-C power adapter and cable to charge your notebook computer. If you have a device that doesn't connect to this port, you might be able to use an adapter to connect it.
These Mac models have Thunderbolt 3 ports:
- MacBook Pro introduced in 2016 or later
- MacBook Air introduced in 2018 or later
- iMac introduced in 2017 or later
- iMac Pro (all models)
- Mac mini introduced in 2018
- Mac Pro introduced in 2019
If your Mac notebook or desktop computer has more than one port like this, each port supports ThunderBolt 3 and USB-C.
USB-C
Use USB-C with displays and other devices that connect using a USB-C cable. You can also connect a USB-C power adapter and cable to charge your notebook computer. If you have a device that doesn't connect to this port, you might be able to use an adapter to connect it.
MacBook models introduced in 2015 or later have a single USB-C port. This port doesn't support Thunderbolt devices.
If your Mac has only one port like this, it's a MacBook that supports USB-C but not Thunderbolt.
Thunderbolt
Use Thunderbolt or Thunderbolt 2 with displays and other devices that connect using a Thunderbolt cable.
These Mac models have Thunderbolt or Thunderbolt 2 ports:
- MacBook Pro introduced in 2011 through 2015
- MacBook Air introduced in 2011 through 2017
- Mac mini introduced in 2011 through 2014
- iMac introduced in 2011 through 2015
- Mac Pro introduced in 2013
Thunderbolt and Thunderbolt 2 are not the same as Mini DisplayPort . They have the same shape, but use different symbols on the cable and port. However, this port does support Mini DisplayPort for video output, so you can use a Mini DisplayPort cable to connect a Mini DisplayPort display.
Mini DisplayPort
Use Mini DisplayPort with displays that connect using a Mini DisplayPort cable.
These Mac models have Mini DisplayPort:
- MacBook Pro introduced in late 2008 through 2010
- MacBook Air introduced in late 2008 through 2010
- Mac mini introduced in 2009 and 2010
- iMac introduced in 2009 and 2010
- Mac Pro introduced in 2009 through 2012
Mini DisplayPort is not the same as Thunderbolt or Thunderbolt 2 . They have the same shape, but use different symbols on the cable and port.
USB-A
Use USB-A with devices that connect using a USB cable. USB ports are sometimes known by the USB specification of the port, such as USB 2 or USB 3.
Left to right: power, two Thunderbolt, USB-A, and Audio-Out.
HDMI
Use HDMI with displays and TVs that connect using an HDMI cable.
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Ethernet
Use Ethernet with networks and devices that connect using an Ethernet (RJ45) cable.
FireWire
Use FireWire with devices that connect using a FireWire 400 or FireWire 800 cable.
SD card
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Use the SD card slot with SD, SDHC, SDXC, MMC, and UHS-II media cards, such as those used by digital cameras.
Audio
Use Audio-Out — or — with headphones, speakers, and other audio-output devices that connect using an audio cable that has a 3.5 mm (1/8 inch) audio jack.
Use Audio-In with a microphone or other audio-input device that connects using an audio cable that has a 3.5 mm (1/8 inch) audio jack.
Power
Use the power port , if available, to connect your computer to AC power using a MagSafe cable or adapter. This port isn't available on newer Mac notebook computers, which use Thunderbolt 3 or USB-C for power and charging. Learn more about power adapters and cables for Mac notebook computers.
Learn more
USB port types and names
USB (Universal Serial Bus) is an industry standard for connecting computers and other devices. It's available with many types of ports, and each type has a unique shape. On Mac computers, USB is available with these ports, depending on your Mac model:
USB-A
Type USB-A ports are commonly called USB, USB 2, or USB 3 ports, depending on the USB specification they support. They aren't reversible, so a USB-A connector plugs into the port only when oriented correctly.
USB-C
Type USB-C ports are available as either standard USB-C ports or Thunderbolt 3 ports that also support USB-C connections. They both look the same, and the connector plugs into the port in either orientation.
Learn more about identifying the ports on your Mac, as well as the adapters and cables you can use to connect older devices to type USB-C ports.
USB specifications
USB specifications are important primarily when you want the most speed and power for your USB device, or your device needs more power or is using too much power. Every USB port supports a particular USB specification, which determines the port's maximum>USB specifications on MacData transferPowerUSB 3.1 Gen 2
Also known as USB 3.2 Gen 2
Up to 10 GbpsUp to 15W at 5VUSB 3.1 Gen 1
Also known as USB 3.2 Gen 1 or USB 3
Up to 5 GbpsUp to 900 mA at 5VUSB 2.0
Up to 480 MbpsUp to 500 mA at 5VUSB 1.1
Up to 12 MbpsUp to 500 mA at 5V
To learn which specification is supported by a type USB-A or type USB-C port on your Mac model:
- Choose Apple menu > About This Mac, click Support, then click Specifications.
- Check the System Information app for more details, including about USB devices connected to USB ports on your Mac. Select USB in the sidebar, then select a USB bus on the right.
Get the best performance from your USB devices
USB specifications all work with each other, but speed and power are limited by the cable or device that uses the earliest specification. For example, if you connect a USB 3 device to USB 2 port, your device is limited to USB 2 speeds, and it can't draw more power from the port than can be delivered over USB 2. In other words, to get the best performance, make sure that the USB port on your Mac and the USB cable to your device meet or exceed the USB specification of the device itself.
If your Mac doesn't recognize a USB device after you plug it into your Mac:
- Check all connections: Unplug the device from your Mac, then plug it back in, and make sure that all cables and adapters are securely connected at both ends. Test with another cable or adapter, if available.
- Plug the device directly into your Mac instead of a USB hub or other device, and if necessary test with a different USB port on your Mac or device.
- Some devices need their own software, such as drivers or firmware. Others work without additional software. Check with the maker of your device, and install all available Apple software updates as well.
- If your device came with an AC power adapter, use it. Some devices can be powered by the USB port on your Mac. Others need more power than your Mac can provide.
- Restart your Mac.
Learn more
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- USB 3 devices can create wireless interference that affects Wi-Fi and Bluetooth devices. Learn how to resolve Wi-Fi and Bluetooth issues caused by wireless interference.
- Mac notebook computers with USB-C or Thunderbolt 3 can charge over that port using a compatible USB-C power adapter and cable.