What it does

Connect over Modbus TCP, UDP and RTU over TCP on Wi-Fi or Ethernet, USB RS-485 adapters (FTDI, CH340, CP210x, PL2303) and Bluetooth SPP adapters (HC-05/HC-06).
Read and write coils, discrete inputs, holding and input registers (FC01–06, 15, 16) in 11 data types and four byte orders, with scaling and units.
See the bytes: a live TX/RX traffic monitor with filters.
Find devices: unit-ID scanner and register-range scanner.
Diagnose: FC08 diagnostics, FC17 server ID, FC43/14 device identification, FC22 mask write, FC23 read/write and a raw frame sender.
Simulate: turn the phone into a Modbus slave over Wi-Fi, USB or Bluetooth.
Record values for hours with the screen off, chart them and export CSV in the same layout as ModbusBB for Windows.
Alarms: notifications, alarm sound and write actions when a value crosses a limit.
Works with the desktop: opens and saves ModbusBB .mbws workspaces and register maps.

Free and Premium

Free (with ads)	Premium
1 connection over TCP, UDP or RTU over TCP	Several connections at once, USB RS-485 and Bluetooth
Read/write FC01–06, 15, 16 in all data types	Device tools, raw frames, unit-ID and register scanners
Traffic monitor and built-in device templates	Recording, trend chart, CSV export and alarms
	Slave simulator, import/export of maps and workspaces, no ads

Premium is available monthly, yearly (with a 7-day free trial) or as a one-time lifetime purchase through Google Play.

Your Modbus data stays on your phone. Read the Android section of the privacy policy.

ModbusBB 2.1 for Windows adds RTU/ASCII on COM ports, a scriptable CLI and more. Download the free trial.