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Limits

Audio​

  • 48 kHz only. Encoders send L24. Decoders play L24 and L16.
  • 1 to 8 channels.
  • Clock drift is corrected by dropping or repeating single frames, not by resampling.
  • Each board's port is 100 Mbit/s.

Serial server​

  • One USB serial adapter, no hub; up to 4 ports.
  • Up to 3 clients per port.
  • No flow control, no break, and no RS-485 direction control from RTS.
  • FTDI FT232H, FT2232H and FT4232H are not supported yet.

USB/IP server​

  • One device, no hubs, one host at a time.
  • Only the configuration the board enumerated the device with.
  • Transfers of at most 127 packets.
  • Isochronous transfers haven't been tested.

See USB/IP server.

Security​

  • No HTTPS. The admin password travels unencrypted, in HTTP Basic auth.
  • The serial sockets and USB/IP have no password or encryption: use their allow lists.

Hardware​

  • The M5Stack Unit PoE-P4X (rev 3.x silicon) isn't supported.

Not tested yet​

  • Dante hardware: decoders playing a Dante stream, and a Dante device as PTP grandmaster. Encoders to Dante receivers work.
  • The Windows USB/IP setup script
  • Isochronous USB transfers

Compatibility​

PTP runs over UDP/IPv4. Firmware from before that change ran PTP over Ethernet directly, so update every board: old and new firmware won't share a clock.