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USB Physical and Electrical Layer
8 Lessons-
StartDP and DM: how USB sends a single bit on two wires
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StartUSB connectors and cables: Type-A, Type-B, Type-C, micro, mini
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PreviewNRZI encoding, bit stuffing, and the sync field
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StartThe pull-up trick: how the host knows your device's speed
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PreviewJ state, K state, SE0, reset, and end of packet
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PreviewVBUS power and current limits
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StartSelf-powered vs bus-powered devices
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PreviewUSB clock accuracy and what happens when it is wrong
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USB Protocol Concepts
8 Lessons-
StartUSB topology: the tiered star (host, root hub, tiers, upstream/downstream ports, compound devices)
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StartSee the topology on your own machine — hubs, the device tree, and the 127-address limit
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StartThe four transfer types and when each is used
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StartPacket, transaction, transfer, frame: what contains what
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StartUSB packet types: Token, Data, Handshake
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StartCapture real USB traffic on your own machine (Wireshark + USBPcap)
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StartEndpoints and pipes: the channels inside a USB device
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StartDescriptors at a glance: the device's passport
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