This is a bit off topic - I don’t formally work with this product line - but the latest WiSP H2 firmware (and Digi Connect SP, EM, ME H2 firmware) includes a simple Modbus Bridge so you can now bridge Modbus/TCP into serial RTU/ASCII. I think you need the 4MB flash version of the ME to gain the Modbus Bridge.
Function is much like the Digi One IA or Modicon CEV (not the fancier IAP). This is a cut from the Release Notes:
USING MODBUS BRIDGE
This image includes a Modbus protocol bridge. Modbus is one of the most common “third party” interfaces for industrial equipment. The full protocol specification can be found at www.modbus.org
The Modbus Bridge functionality enables Masters and Slave to communicate using any combination of the 3 official dialects:
- Modbus/TCP transported by TCP/IP or UDP/IP
- Modbus/RTU transported by serial, TCP/IP, or UDP/IP
- Modbus/ASCII transported by serial, TCP/IP, or UDP/IP
One-serial port bridges are defined by the role of the attached serial device. Selecting the “Industrial Automation” serial port profile enable you to define either:
- Serial Modbus master accessing remote IP-based Modbus slaves
- Remote Modbus masters sharing a serial Modbus slave(s).