Ethernet Parameters: Number of ports: 1 Interface standard: RJ45 LAN Ethernet speed: 10/100 Mbps Data cache: 6 KB Protection: 2 kV electromagnetic isolation Network protocols: IP, ARP, TCP, UDP, ICMP, IGMP, DHCP Serial Port Parameters: Number of ports: 1 Interface standard: TTL serial port, 2.54 mm pin, 3.3 V or 5 V logic level Baud rate: 300 to 921,600 bps Data bits: 5, 6, 7, 8, or 9 Stop bits: 1 or 2 Parity: None, odd, or even Flow control: None Cache: 2 KB Supporting Software: Parameter configuration: Network configuration software, serial AT commands Module testing: Test software for network and serial communication Basic Parameters: Operating voltage: DC 3.3 V or 5 V Operating current: 200 mA at 5 V Pin Definitions: 1. RESET: Factory reset pin; active low on power-up detection 2. DIR: RS485 transmit/receive direction control pin 3. TCPCS: TCP client connection status indicator; outputs low when connected successfully 4. RUN: Module operation status indicator; accepts 2 Hz square wave input 5. GND: Ground pin 6. 3.3V: 3.3 V DC power input (≥200 mA); can be used interchangeably with 5 V supply 7. GND: Ground pin 8. 5V: 5 V DC power input (≥200 mA); can be used interchangeably with 3.3 V supply Color: Blue + silver Material: Plastic + metal Package Contents: 1 × CH9121 Serial-to-Ethernet Module Note: Color may vary slightly due to lighting and screen settings. Dimensional tolerance: ±1–3 cm.