CH9121 Serial to Ethernet Module TTL TCP/IP 3.3V 5V STM32
CH9121 Serial to Ethernet Module TTL TCP/IP 3.3V 5V STM32
CH9121 Serial Port to Ethernet Network Module — Industrial-Grade TTL Connectivity
Bridge the gap between serial devices and Ethernet networks with the CH9121 Serial to Ethernet Network Module. Designed for industrial microcontroller applications, this compact module supports STM32, 51-series MCUs, and virtually any TTL-level serial device. With dual voltage support (3.3V and 5V), plug-and-play TCP/IP stack, and robust 2KV electromagnetic isolation, it's the go-to solution for engineers and makers who need reliable, high-speed serial-to-network conversion.
Made in Mainland China.
Key Features
- TCP/IP Protocol Stack: Supports IP, ARP, TCP, UDP, ICMP, IGMP, DHCP — no external stack library needed
- Dual Voltage Support: Works at 3.3V or 5V DC for maximum compatibility with your existing hardware
- Fast Ethernet: 10/100 Mbps RJ45 interface with 6K byte data cache
- Flexible Baud Rate: 300 to 921,600 bps — covers the full range of serial communication speeds
- 2KV Electromagnetic Isolation: Industrial-grade protection for noisy environments
- Easy Configuration: Set up via network configuration software or serial AT commands
- RS485 Ready: DIR pin for RS485 send/receive switching control
Technical Specifications
| Parameter | Specification |
|---|---|
| Ethernet Interface | RJ45, 10/100 Mbps |
| Ethernet Data Cache | 6K bytes |
| Network Protocols | IP, ARP, TCP, UDP, ICMP, IGMP, DHCP |
| Serial Interface | TTL, 2.54mm pin header |
| Voltage | 3.3V or 5V DC |
| Operating Current | 200mA @ 5V |
| Baud Rate | 300 – 921,600 bps |
| Data Bits | 5, 6, 7, 8, 9 |
| Stop Bits | 1, 2 |
| Parity | None / Odd / Even |
| Serial Cache | 2K bytes |
| Electromagnetic Isolation | 2KV |
| Material | Plastic + Metal |
| Color | Blue + Silver |
Pin Description
- RESET — Factory reset pin; active low, detected at power-on
- DIR — RS485 receive/send switch control pin
- TCPCS — TCP client mode connection status indicator; outputs low on successful connection
- RUN — Module running status indicator; outputs 2Hz square wave
- GND — Power ground
- 3.3V — 3.3V DC power input (>200mA); alternative to 5V supply
- GND — Power ground
- 5V — 5V DC power input (>200mA); alternative to 3.3V supply
What's in the Box
- 1 × CH9121 Serial Port to Ethernet Network Module
Note: Due to lighting and display variations, the actual color may differ slightly from product images. Measurement tolerance: ±1–3 cm.
Learn More About Industrial Networking Standards
For background on industrial communication protocols and network standards, visit the National Institute of Standards and Technology (NIST) Networking Resources.
Frequently Asked Questions
Q: Is the CH9121 Ethernet module compatible with both STM32 and 51-series microcontrollers?
A: Yes. The CH9121 Serial to Ethernet Network Module supports TTL-level serial communication at 3.3V or 5V, making it directly compatible with STM32, 51-series MCUs, Arduino, and most other microcontrollers that use a standard UART/serial interface.
Q: How do I configure the CH9121 module's network settings?
A: The CH9121 module can be configured in two ways: using the included network configuration software (run over Ethernet) or by sending AT commands directly over the serial port. This makes it easy to set IP address, port number, baud rate, and operating mode (TCP server, TCP client, UDP, etc.) without additional hardware.
Q: Can this module be used in industrial environments?
A: Absolutely. The CH9121 module features 2KV electromagnetic isolation on the Ethernet interface, making it well-suited for industrial automation, factory floor equipment, PLCs, and other environments where electrical noise is a concern.
Q: What network protocols does the CH9121 module support?
A: The module's onboard TCP/IP stack supports IP, ARP, TCP, UDP, ICMP, IGMP, and DHCP — covering the vast majority of use cases for device-to-network and device-to-cloud connectivity in both commercial and industrial applications.