Tech-dat/Interface-dat/USB-SDK-dat/USB-SDK-dat.md
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- [[CONN-USB-dat]] - [[USB-SDK-dat]] - [[cable-USB-dat]]
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-- [[USB-SDK-dat]] - [[CONN-USB-HDK-dat]]
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+- [[USB-SDK-dat]] - [[CONN-USB-HDK-dat]] - [[USB-SDK-type-C-dat]]
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- [[CONN-USB-dat]] - [[conn-dat]]
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Tech-dat/Interface-dat/USB-SDK-dat/USB-SDK-type-c-dat/USB-SDK-type-c-dat.md
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+## debug info
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+### keeping dropping
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+`USB Serial/JTAG Internal Switch`
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+The S3 has an internal USB Serial/JTAG controller. If your code (or the factory firmware) initializes the USB peripheral in a way that conflicts with the hardware connection, the PC will "drop" the device as soon as the code starts running (usually 1-2 seconds after boot).
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+Test: Hold the `BOOT` button (`GPIO 0 to GND`), then press RESET, then release BOOT. If the device stays connected to the PC in this state, your hardware is fine, and the issue is your firmware or USB configuration.
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## info and knowledge
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### USB-C vs. USB Type-C: Is There a Difference?