- The number and type of USB ports on Raspberry Pi depends on the model. The Raspberry Pi Model B is equipped with two USB 2.0 ports; the B+, 2B, 3B and 3B+ have four USB 2.0 ports. The Pi 4 has two USB 2.0 ports and two USB 3.0 ports. In all models prior to the Pi 4, the USB ports connect to a combo hub/Ethernet chip, which is itself a USB device connected to the single upstream USB port on BCM2835. On the Pi 4, the USB hub chip is connected to the SoC using a PCIe bus.
- On the Model A and Zero range, the single USB 2.0 port is directly wired to the SoC.
- The USB ports enable the attachment of peripherals such as keyboards, mice, webcams that provide the Pi with additional functionality.
- There are some differences between the USB hardware on the Raspberry Pi and the USB hardware on desktop computers or laptop/tablet devices.
- The USB host port inside the Pi is an On-The-Go (OTG) host as the application processor powering the Pi, BCM2835, was originally intended to be used in the mobile market: i.e. as the single USB port on a phone for connection to a PC, or to a single device. In essence, the OTG hardware is simpler than the equivalent hardware on a PC.
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