BestParts CH9121 Microcomputer Networking Module Instruction Manual

Introduction

The BestParts CH9121 Microcomputer Networking Module is a serial port to Ethernet adapter designed for transparent data transmission between serial devices and a network. It integrates a TCP/IP protocol stack, enabling seamless communication for various applications.

Key Features:

• Equipped with CH9121 network serial port transparent transmission chip.
• Supports two-way transparent transmission of network data packets and serial port data.
• Serial port TTL level compatible with 3.3V and 5V systems.
• Supports full-duplex and half-duplex serial port communication, including RS485 transceiver automatic switching.
• Adjustable serial port baud rate from 300bps to 921600bps.
• Operates on 3.3V/5V power supply.
• Features 4 working modes: TCP CLIENT, TCP SERVER, UDP CLIENT, and UDP SERVER.

Setup

This section guides you through the physical setup and initial connections of your CH9121 module.

Figure 1: Two CH9121 modules and pin headers included in the package.

Figure 2: Physical dimensions of the CH9121 module.

Figure 3: Detailed view of the RJ45 port and the CH9121 chip on the module.

Figure 4: Pinout diagram for connecting the module to a microcontroller or other devices.

Connection Steps:

1. Power Supply: Connect 3.3V or 5V power to the appropriate pins on the module. Ensure correct polarity.
2. Serial Connection: Connect the module's TXD, RXD, and GND pins to your microcontroller (e.g., STM32 UART) or other serial device. For RS485, ensure the transceiver automatic switching is correctly configured.
3. Ethernet Connection: Plug a standard RJ45 Ethernet cable into the module's Ethernet port and connect it to your network.
4. Configuration: Use the provided upper computer software or serial AT commands to set network parameters such as IP address, port, and operating mode.

Figure 5: Example connection diagrams for different operating modes.

Operating Modes and Configuration

The CH9121 module supports four primary operating modes, configurable via AT commands or dedicated software.

• TCP CLIENT Mode: The module actively connects to a TCP SERVER. Once connected, it enables bidirectional transparent transmission of network and serial data. The TCP SERVER's IP must be accessible to the module. This mode supports random local ports and domain name access for remote services.
• TCP SERVER Mode: The module listens for client connection requests on a specified local port. Upon connection, it facilitates two-way transparent data transmission. The TCP CLIENT's IP must be able to reach the module. Configurable parameters include operating mode, device IP, subnet mask, default gateway, and device port. This mode supports only one TCP client connection.
• UDP CLIENT Mode: The module sends and receives UDP packets to a specified remote UDP server.
• UDP SERVER Mode: The module listens for incoming UDP packets on a specified local port.

AT Command Configuration:

The module's parameters can be set using AT commands sent over the serial port. The baud rate for serial communication can be configured from 300bps to 921600bps.

Maintenance

To ensure the longevity and optimal performance of your CH9121 module, follow these maintenance guidelines:

• Keep Clean: Regularly inspect the module for dust or debris. Use a soft, dry brush or compressed air to gently clean the board and connectors.
• Environmental Conditions: Operate the module within its specified temperature and humidity ranges. Avoid exposure to extreme conditions, moisture, or corrosive substances.
• Secure Connections: Periodically check all cable connections (power, serial, Ethernet) to ensure they are secure and free from damage. Loose connections can lead to intermittent operation or data loss.
• Power Supply: Use a stable and appropriate power supply (3.3V/5V) to prevent damage to the module.
• Firmware Updates: Check the manufacturer's website for any available firmware updates. Updates can improve performance, add features, or fix bugs. Follow update instructions carefully.

Troubleshooting

If you encounter issues with your CH9121 module, refer to the following troubleshooting tips:

• No Power/LEDs Off:
  • Verify the power supply voltage (3.3V or 5V) and ensure it is correctly connected.
  • Check for any short circuits on the power lines.
• No Network Connection:
  • Ensure the Ethernet cable is securely plugged into both the module and the network device.
  • Check network settings (IP address, subnet mask, gateway) configured on the module.
  • Confirm that the network device (router/switch) is functioning correctly.
  • If using DHCP, ensure the DHCP server is active and assigning IP addresses.
• Serial Communication Issues:
  • Verify the serial port connections (TXD, RXD, GND) are correct.
  • Check the baud rate settings on both the module and your serial device; they must match.
  • Ensure the serial port level (TTL 3.3V/5V) is compatible with your device.
  • If using RS485, confirm the automatic switching is correctly handled.
• Module Unresponsive to AT Commands:
  • Confirm the serial connection and baud rate are correct.
  • Ensure the module is in a state where it can receive AT commands (e.g., not actively transmitting data in a transparent mode).
  • Check the AT command format and termination characters.

Specifications

Warranty and Support

For warranty information and technical support, please refer to the product packaging or contact BestParts customer service directly. Specific warranty terms may vary by region and retailer.