EXSYS EX-3655 M.2 Dual-Port RS-232 Serial Interface Card

With a 256-byte FIFO buffer and data rates up to 921.6 Kbps per port, the EXSYS EX-3655 turns a single M.2 A+E key slot into two high-performance RS-232 serial ports. This low-profile 2230 card is engineered for industrial PCs, embedded systems, and compact workstations where reliable legacy connectivity is non-negotiable.

Overview

The EX-3655 is a native M.2 (NGFF) interface card that adds two RS-232 serial ports through a single A+E keyed M.2 2230 slot. Built around the ASIX AX99100 controller, it delivers true 16C950 UART compatibility, ensuring seamless operation with legacy software and hardware. The card supports hardware and software flow control, remote wake-up, and advanced power management, making it suitable for always-on systems.

What stands out

• Two RS-232 ports from one M.2 slot – ideal for space-constrained builds
• Selectable 5V or 12V power output on pin 9 for powering serial peripherals
• 256-byte FIFO buffers reduce CPU overhead and prevent data loss
• Broad OS support: Windows 7/8/10/11, Linux, and macOS
• Remote wake-up and power management for energy-efficient operation

Technical details

• Host interface: M.2 (NGFF) A+E key, 2230 form factor
• Chipset: ASIX AX99100
• Serial ports: 2x RS-232, DB9 male connectors via included cable
• Max data transfer rate: 921.6 Kbps per port
• FIFO buffer: 256-byte transmit/receive per port
• UART compatibility: 16C950
• Flow control: Hardware (RTS/CTS), Software (XON/XOFF)
• Power output on pin 9: Selectable 5V or 12V
• Operating systems: Windows 7/8/10/11, Linux, macOS
• Remote wake-up support: Yes
• Power management support: Yes

Our verdict

The EXSYS EX-3655 is a compact, reliable solution for adding legacy serial ports to modern M.2-equipped systems. Its selectable power output and robust UART make it a standout choice for industrial and embedded applications.