BaudHub

Purpose

BaudHub is a native Modbus RTU and Modbus TCP debugger and serial terminal for Mac. Connect a USB-RS485 or RS232 adapter or a Modbus TCP device, read your first register value in minutes, see the exact frame behind every value, and write settings safely with automatic read-back. A built-in Modbus slave simulator lets you test a PLC, SCADA system or master without hardware.

BaudHub is made for commissioning engineers, PLC and SCADA integrators, solar, battery, EV charger and heat pump installers, energy meter technicians, and embedded and IoT developers. No account, no analytics, no ads.

Key Features

• Modbus master: RTU over serial and Modbus TCP; coils, discrete inputs, holding and input registers; single and multiple writes
• Adapters: FTDI, CP210x, PL2303 and CH34x USB adapters, with driver guidance when a chip needs one
• Decoding: 28 display formats (16-, 32- and 64-bit integers, float, BCD, hex, binary, ASCII), all 32-bit byte orders, 0- or 1-based addresses, scaling and units
• Raw data: each value in several formats side by side, with the raw HEX and the frame it came from
• Frame log: requests, replies, exception codes and timeouts explained in plain language, with filters, search and CSV export
• Bus scan: unit IDs, baud rates and parity, plus a guided unit address change
• Safe writes: read-only by default; preview, confirm, send once, read back and audit log
• Charts: live series with time windows, thresholds and a link from any sample to its frame
• Slave simulator: Modbus RTU and TCP slave with several unit IDs and changing values
• Serial terminal: ASCII and HEX, timestamps, send history and recording
• Templates: SunSpec, SMA, Fronius, SolarEdge, KOSTAL, KEBA, go-e, Chint DDSU666/DTSU666, Schneider PM5xxx and Eastron SDM630, each with its source and verification status
• Field-ready: stale values are marked, connections return after a replug or wake, sessions export as one package, and extra app instances run parallel jobs

Requirements

Getting Started

1. Plug in your adapter, or make sure your Mac can reach the device's IP address.
2. Choose New Connection… (⌘N). For serial, pick the port and enter the device's baud rate, data bits, parity and stop bits (often 9600 8N1). For TCP, enter the host and port.
3. In Add Device, enter the unit ID and choose a template, or add a register block with the function, start address, count and format from the vendor's register map.
4. When the device answers, its value appears in the list. Select a row to see the value in other formats and the raw data it came from.

Don't know the unit ID or line settings? Use Scan Bus… on the connection.

Plans and Purchases

• Free: one device each in the Serial and TCP workspaces, two register blocks per device, a scan of unit IDs 1–16, the HEX frame log, charts, the terminal and one simulator.
• BaudHub Pro (one-time purchase): unlimited devices, full scan, frame explanations, writes, all display formats, export, template import and more simulators.
• 7-Day and 30-Day Site Passes: every Pro feature for a job. They do not renew and return to Free when they end.

To use your purchase on another Mac, sign in with the same Apple Account and choose Restore Purchases in BaudHub Settings or on the plan sheet. Refunds are handled by Apple at reportaproblem.apple.com. See the Terms of Use (EULA).

Troubleshooting

My serial port is not in the list

Plug the adapter in and click the refresh button next to Port. If BaudHub shows Driver needed for …, the chip (often CH343, CH9102 or a newer PL2303) needs the vendor's driver: install it from the link and replug the adapter. Still nothing? Try another USB cable; some cables carry power only.

"Port in use"

Another app or BaudHub instance holds the port, for example screen, the Arduino IDE or another debugger. Close it there and retry.

Connected, but no values

Open the Frame Log tab and look at the colors:

• Yellow (timeout): the device did not answer. Check the unit ID (or scan), swap A and B, and confirm the device has power.
• Red (garbled reply): the baud rate or parity usually differs from the device. Compare with its nameplate.
• Orange (exception): the device is online but refused the request, usually an address out of range or the wrong function (input vs holding registers).
• Grey: data arrived without a request; another master may be active on the bus.

A Modbus TCP connection is refused or reset

Many inverters and gateways accept only one Modbus client. Disconnect evcc, Home Assistant or another computer first. Check that Modbus TCP is enabled on the device (KEBA and go-e ship with it off), that the port is right, and that your Mac and the device are on the same subnet. If macOS asked about local network access, allow BaudHub in System Settings › Privacy & Security › Local Network.

Values look wrong

Absurd numbers usually mean the wrong format or byte order: select the row and compare the same value shown in other formats. Values off by 10× or 100× need a scale factor. Values that belong to the neighboring register point to a 0- vs 1-based address mix-up.

Write is unavailable

Unlock writes with the lock in the toolbar (⌘L). Writes also stay unavailable while disconnected, on registers marked read-only, in imported sessions, and on the Free plan. The lock closes again after every reconnect.

Everything turned grey

The link dropped, for example after an unplug, a device restart or sleep. BaudHub reconnects on its own; grey values are kept but marked stale until fresh replies arrive.

Another computer cannot reach my simulator

Use one of the listen addresses the simulator shows, check that macOS Firewall allows BaudHub, and make sure the simulator is still running. When a USB adapter sits in between, set the master's timeout to 100 ms or more.

Frequently Asked Questions

What is the difference between Modbus RTU and Modbus TCP?

Modbus RTU runs over a serial line such as RS485 or RS232. Modbus TCP carries the same requests over Ethernet or Wi-Fi. BaudHub supports both; this version does not open Modbus RTU over TCP connections.

Is there a Modbus Poll alternative for Mac?

BaudHub is a native Mac app for reading, writing and scanning Modbus devices, with a slave simulator and a serial terminal, so you don't need to run Windows tools in a virtual machine.

Can I test without a device?

Yes. Choose New Simulator… in the Simulator workspace and start it. Then connect to it from BaudHub, or from your own master, PLC or SCADA system, using the address the simulator shows.

Can I run two jobs at the same time?

Yes. Choose File › New BaudHub Instance to open another BaudHub with its own workspace, for example one for a serial bus and one for a TCP gateway.

Are the device templates verified?

Each template names the vendor document it was built from and shows its verification status. Check critical registers against your device's documentation before writing. Vendor names identify register maps only; BaudHub is not affiliated with these companies.

What does a session export contain?

Export Session… saves your connections, devices, register settings, readings and logs as a single file you can share. Imported sessions open read-only.