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Supported Devices

kvm-serial supports two UART-to-USB-HID bridge chip families.

CH9329

The CH9329 is a command-driven chip where the host sends HID reports over UART and the chip translates them into USB HID input on the target machine.

  • Simple command-style protocol
  • 4095x4095 12-bit absolute mouse coordinate space
  • Relative mouse support
  • Keyboard boot protocol

Protocol reference: CH9329 Protocol

CH9350L

The CH9350L is a paired-chip extender. kvm-serial replaces the lower computer (LC) side in software and drives an upper computer (UC) module that presents USB HID to the target machine.

  • Four working states selected via UC dipswitches
  • State 0/1: full HID descriptor passthrough with pairing handshake
  • State 2: BIOS keyboard + relative mouse for legacy BIOS / UEFI CSM
  • State 3: BIOS keyboard + absolute mouse for modern OS use
  • State 4: BIOS keyboard + absolute mouse + HID Digitizers for multi-monitor setups
  • 65535x65535 16-bit absolute mouse coordinate space in states 3/4
  • Heartbeat and keep-alive synchronization

Protocol reference: CH9350L Protocol

Hardware Notes

  • CH9329 hardware is commonly sold as pre-assembled cables or small modules.
  • CH9350L hardware is more commonly sold as breakout boards with dipswitches.
  • Both families are typically used with a USB-to-UART adapter such as CP2102, CH340, FTDI, or similar.