Template: Pico-ETH-CH9121 Spec

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Ethernet To UART Converter For Raspberry Pi Pico, 10/100M Ethernet, Enabling Network Communication Through UART.


  • Standard Raspberry Pi Pico header, supports Raspberry Pi Pico series.
  • Onboard Ethernet to UART transparent transceiver, 2-CH UART, standalone transparent transmission for each channel.
  • Onboard jumpers for pin configurations.
  • Embedded Ethernet MAC and PHY layers.
  • Bi-direction transparent data transmission between UART and Ethernet.
  • 10/100M, full-duplex/half-duplex auto-negotiation Ethernet interface, 802.3-compliant.
  • Auto-MDI/MDIX, detect and switch cable type automatically.
  • Supports DHCP auto-obtained IP and DNS domain access.
  • Network parameter configuration like chip operating mode, port, IP, via host computer software or UART command
  • Full-duplex or half-duplex UART communication supports RS485 RX/TX auto switch (external RS485 controller required).
  • Supports virtual serial port software (provided).
  • KEEPALIVE mechanism support.


  • Operating votlage:3.3V/5V
  • Operating mode: TCP/UDP
  • UART TTL: 3.3V / 5V compatible
  • Operating temperature: ~40°C ~ 85°C
  • Operating current: 140mA
  • Baudrate: 300bps ~921.6Kbps
  • Dimensions: 74.54 x 21.00 (mm)
  • Storage Condition: -55°C ~ 125°C



About the CH9121

The CH9121 is a transparent network serial port chip that supports bidirectional and transparent transmission of serial port data and network data. It supports four working modes: TCP CLIENT/SERVER and UDP CLIENT/SERVER. The serial port baud rate ranges from 300bps to 921600bps. Before using, you should set network and serial port parameters for the chip by the NetModuleConfig.exe software or serial commands. After the configuration is complete, the CH9121 saves the configuration parameters to the internal storage space. After the chip is reset, the CH9121 could work based on the saved configuration values.

Default Parameters

The UART 2 is disabled and the UART 1 works in TCP CLIENT mode by default.

  • The network parameters of UART1 (port 1)
    • Device IP:
    • Subnet mask:
    • Device port: 2000
    • Target IP:
    • Target port: 1000
  • The Serial parameters of port
    • Baud rate: 9600
    • Timeout: 0
    • Data bit: 8
    • Stop bit: 1
    • Parity bit: None
    • Clear buffer: Never