Modbus-Droid / MobileModbus

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Modbus-Droid (or as it is called on the Blackberry app world market – Mobile Modbus) was designed to be a simple Modbus TCP client / scanner. I wanted to have something similar to Modscan32, a program I use a lot at my work, but on my phone. My goal was to provide the simplicity of Modscan32, so I put the information I change the most – the register type, the register offset, and the quantity of registers to read – all right up front. The other stuff, like IP address, poll time and what-not are on a settings screen.

Download the app here: market://search?q=pname:com.bencatlin.modbusdroid
or scan this QR code:

Modbus-Droid is also open source, and built on an open source library – Modbus4J (that I had to modify a little for my needs).

The source code is available on GitHub here:
and and archive that stops at version 1.0 is still available on launchpad here:
Both of these project hosting sites include my modified version of the Modbus4J.


  • Intuitive Interface (if you are familiar with modbus)
  • Time-based polling
  • Write single holding registers and holding coils just by touching the value
  • Ability to view data in multipe formats, including binary for registers for people who like to use the register space for combined boolean data (like I do at work).
  • Write dialogs allow you to write data in the format you are displaying (i.e. a register displayed as binary allows you to set individual bits true and false inside the register)

Known Issues/bugs on 1.0

  • No way to handle byte-swapped data sources. I have found a place in the Modbus4J library I think I could handle this, but it was more surgery than I was comfortable with. I might tackle this somewhere down the road.
  • Some of the error messaging (like the connection lost error) results in a pretty cryptic or ‘programmer’ type of message. Hopefully I’ll get to putting in some human-readable text in a future version if I have time.
  • And I’m sure there a few others I haven’t found yet, if you find some please report the bugs on GitHub
  • This isn’t exactly a bug or issue, but there have been a lot of people contacting me about some compiler errors, or how to get this started in eclipse. Here is a the thing – please make sure you have the SDK installed correctly and can compile a sample project. I really want to help with questions and issues, but I can’t remotely debug your compiler or computer setup issues. This is my hobby project right now (hopefully android development will someday become my day job), and I don’t currently have the time or resources to write a bunch of documentation about it. But fortunately google already did, so reference the android SDK documentation before emailing me. Also, if you are still experiencing problems after getting a sample project to compile in eclipse and install in the emulator or your device, please refer to the GitHub site for the project to report bugs, or post questions, not the comments here.