Problem to read/write to HUM-N or AQ-N via modbus

i just bought one HUM-N, one AQ-N and one USB-RS485. I want to test the modbus communication between HUM-N or AQ-N and PC/Win7.
The device is powered (24VAC + Gnd) and connected to the PC via USB-RS485 (Net+ and Net-).

As HUM-N and AQ-N devices has no LCD display, how can i know the initial communication parameters (baud rate, stop bits, parity) and the initial device modbus address ?
Thanks for any clue

I reply to myself :
Using the T3000 application and the Discover ([Alt-D]) tool, i found the baud rate (115200) and the modbus address (9 for HUM-N and 254 for AQ-N). I can change the modbus ID and read the device’s registers with the Modbus Poll tool and then modify some registers with my own tool.

Perhaps could the default baud rate and ID values be specified in the device’s documentation ?


Sorry for the slow reply Alain, I am travelling just now.

As you discovered by now, the best way to get started integrating is to connect with the T3000 front and get familiar with some of the settings and features. The front end can discover the devices over Ethernet and RS485 connections, either bacnet or modbus protocol, and any baud rate or IP settings.

If you have any questions or issues with the integrating just send an email or post here in the forums.


Can the T3-LB-Asix discover a HUM-C connected via Modbus?
Ted Northrup
Queens Oaks

T3_xB_Asix is an earlier model which can discover modbus slave device via only Modbus. The updated model is the T3_xB_ARM which can support both bacnet MSTP and modbus.