CH9121 Serial to Ethernet Module TTL TCP/IP for STM32 51 Microcontroller

CH9121 Serial to Ethernet Module Overview This CH9121 module provides a straightforward bridge between serial interfaces and Ethernet networks, making it well suited to industrial microcontroller projects. Operating at 10/100Mbps, the onboard Ethernet controller handles network communication through a single RJ45 port, while the integrated data cache of 6 KB supports smooth TTL serial transmission. The module accepts both 3.3V and 5V logic levels, so it can be paired with a wide range of development boards and microcontrollers, including STM32 and 51 series devices. Simple Integration with Existing Projects Because the module manages the TCP/IP protocol stack internally, you can connect it directly to your microcontroller's UART pins without needing additional protocol handling in your firmware. This keeps the integration process straightforward, whether you are adding network connectivity to a sensor node, a data acquisition unit, or an industrial control system. The RJ45 interface uses the standard connector, so you can plug in a regular Ethernet cable and start communicating over your local network without specialised tools or adapters. Reliable Performance for Industrial Use The CH9121 is designed with industrial applications in mind, offering stable performance across a range of operating conditions. The single-port Ethernet interface keeps the wiring simple, while the 6 KB data cache helps maintain consistent data flow during transmission. With support for both 3.3V and 5V supply voltages, the module gives you flexibility when integrating it into existing circuits, reducing the need for additional level-shifting components. This makes it a practical choice for engineers and hobbyists working on networked embedded projects.