If you need only viewer: https://play.google.com/store/apps/details?id=net.sagram.hmi_modbus_viewer.
Also implemented communication through Bluetooth (Modbus RTU), can be used for communication via Bluetooth shield for Arduino and other devices.
Viewing requests and responses in Hex format in the log.
Program interface is based on Drag and Drop principle. Long tap on element in editing mode is used to move that element within workspace.
Most external HMI are using port no. 8000, PLC port usually set to 502.
Read/write functions currently supports Int 16, Int 32, Float, Float swapped, Boolean data types.
Software was tested on HMI panel Weintek MT6070iH, Delta DVP20EX2 PLC, Siemens s7-1200 PLC