MAQ20-COM2: Communication Module; Ethernet, USB, RS-232

Communication Module; Ethernet, USB, RS-232

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The MAQ20 communications module is offered in two models and provides the connection between a host computer and a MAQ®20 Data Acquisition System. MAQ20-COM4 communicates using Ethernet, USB, or RS-485; MAQ20- COM2 uses Ethernet, USB, or RS-232. Ethernet communications use the Modbus TCP protocol and USB communications are based on the Modbus RTU protocol, which RS-485 and RS-232 communications also use. Serial communications over RS-485 can be either 2-wire or 4-wire.

When using the Ethernet interface, up to four simultaneous socket connections are supported and each socket can process up to four simultaneous Modbus TCP transactions. Serial communications over RS-232 or RS-485 can be run at baud rates as fast as 921.6kbps.

A very useful feature of the MAQ20 system is the capability to store acquired data locally for later analysis. This is provided by the easily accessible and removable 4GB micro-SD memory card that is in the MAQ20-COMx module and can be used to log data acquired from all input modules. Each MAQ20-COMx module can interface to up to 24 I/O modules in any combination, allowing high channel counts and great flexibility in system configuration.

To power the system, a 7-34VDC power source is connected to the communications module. Regulated and protected supplies within the module then provide power both to the internal circuits and to all I/O modules in the system. When many high power I/O modules are used in a system, MAQ20-PWR3 load-sharing boost power supply modules can be installed in standard I/O module slots to provide the necessary additional power.

To ensure robustness, the communications interface-to-bus isolation is 50VDC and power input terminals are protected against overvoltage, transient, and reverse connections. As a minimum, a MAQ®20 Data Acquisition System must have a communications module, a backbone, and one I/O module.


  • Connect Host Computer and MAQ®20 System
  • Communicate using Ethernet, USB, RS-485, RS-232
  • Up to 4 Simultaneous Socket Connections with Ethernet
  • Baud Rates to 921.6kbps with RS-232/RS-485
  • Follow Modbus TCP or RTU Protocols
  • Store Acquired Data Locally
  • Interface to up to 24 I/O Modules
  • 50VDC Communications Interface-to-Bus Isolation

Block Diagram


Frequently Asked Questions

Where do I download MAQ20 configuration software?
MAQ20 configuration is best performed with ReDAQ Shape software. We do have other software for download as well. Please check out the Software Download Center.

Note:The "MAQ20-945 Configuration Software Tool" was replaced with ReDAQ Shape software tool in 2017.

Can Dataforth provide calibration reports for modules I purchased?
Yes we can provide calibration reports for the modules that you purchased.

You can either
a) visit to search for Test Report Datasheets by Serial Number or
b) you can send us a list of model numbers and their serial numbers to

Is the calibration of Dataforth modules traceable to NIST standards?
Yes, calibration of Dataforth modules is traceable to NIST standards.

Where do I download the USB drivers for the MAQ20 to be used with ReDAQ Shape?
There are two places that you can download the USB drivers for MAQ20. If you haven't already downloaded ReDAQ Shape, you will be given the option to download the required USB drivers during the installation process. If you already have ReDAQ Shape downloaded and you somehow lost the USB drivers, you can download them from our website. The USB drivers for the 8B isoLynx SLX300 system are identical with the USB drivers for the MAQ20. Visit this link, scroll down to the "Drivers" section on the page and download "USB (Virtual Comm Port Driver)":

How do I save my module configuration in the Configuration Software Tool (MAQ20-945)?
The Configuration Software Tool for MAQ20 does not have project files that can be saved. Any adjustments you make to the configuration of your modules through the Configuration Software Tool will be saved to the modules themselves, and not to a file on your PC. It is only a tool to change the settings in the modules themselves.

Can I export data from ReDAQ shape to a text file or Excel spreadsheet?
Yes, ReDAQ Shape offers the option to export data to a .txt file or Excel spreadsheet live without interrupting the data acquisition process. Simply click the "Open Data File" or "Open Excel File" button in the "Analyze" panel.

Is 4GB the max size for the SD card in the MAQ20-COMx module?
8GB is now the max size for the SD card. Recent shipments of COM modules include 8GB SD cards.

How are unlock keys used to license IPEmotion?
Unlock keys are generated from the serial number of the COM module of the system that you purchased. These unlock codes are also generated based on how many I/O modules are in the MAQ20 system. You won't be able to run the data acquisition process in IPEmotion unless you have entered the correct unlock code for your system and the I/O module count of your system is equal to or below the allotted I/O module count determined when the unlock code was generated.

For example, if you purchased an unlock key for a MAQ20-COM2 with 1 MAQ20-VO, 1 MAQ20-VDN, and 2 MAQ20-BRDG modules, this would correspond to an I/O module count of 4. If you attempted to run the acquisition process with this configuration, it would work perfectly. If you decided to remove the two MAQ20-BRDG modules, you would still be able to run the acquisition process. However, if you were to add a MAQ20-FREQ module to your system, bringing your total I/O module count to 5, IPEmotion will not let you start the data acquisition process until the I/O module count is back to 4 or lower.

If you have more than one MAQ20-COM module in your system, it is not necessary to enter additional unlock codes for the extra COM modules.

How are unlock codes used with ReDAQ Shape?
Unlock codes are generated based on the serial number of the COM module of the system you purchased. If you are running an unlicensed version of ReDAQ Shape you sill have access to all the features of the software, but are limited to 1 hour of usage until the software stops. Entering the unlock code associated with your MAQ20 system will remove the time limit and allow unlimited usage of ReDAQ Shape. You must purchase an unlock code for every COM module you are using in order to have unlimited usage of ReDAQ Shape.

Note: Licenses purchased for the Developer version of ReDAQ Shape are not compatible with the User version, and vice versa.

How do I convert an RMS voltage to its corresponding peak voltage?
To convert an RMS voltage to its corresponding peak voltage, you simply take the RMS voltage value and multiply it by the square root of 2, or roughly 1.414.

For example, 1500Vrms corresponds to a peak voltage of 1500 * 1.414 = 2121 Vp

Does the MAQ20 Python API support USB connection?
Currently, the MAQ20 Python API only supports Ethernet connection.

How long is the delay between the MAQ20 COM module reading data and that data being transferred to the host PC?
The MAQ20-COM2 / -COM4 does not buffer data for transmission, it is only a pass through for communications. The 6ms command/response cycle of acquiring data from the I/O modules in the system also includes the time it takes to transfer data to the host PC.

Is it possible to provide external power supply directly to the backplane rail instead through the MAQ20-COM2 front panel?
The MAQ20-COMx module has to be powered through its power connector and it powers the backbone to power the I/O modules.
If you powered the backbone too, then that power supply would fight the power supply from the COM module and they would likely damage each other.

Can the MAQ20 save data directly to a SQL database?
No, the MAQ20 cannot save or export data directly to a SQL database. ReDAQ Shape can export data directly to a .txt, .csv or Excel file, and then the data could be extracted from those files to be uploaded to a SQL database.

Does the MAQ20-COMx module run the ReDAQ Software or is it run externally on PC?
ReDAQ Shape is ran externally from the MAQ20 system on a host PC running Windows OS, not on the MAQ20-COMx module.

Can I disconnect my MAQ20 from my PC and have the system to continue to log data?
If you start a standard logging process (i.e. clicking "run" in ReDAQ Shape or "store" in IPEmotion), disconnecting your MAQ20 system from the PC will terminate the log.

However, if you use the MAQ20s SD Card Logger, you can start a data log and disconnect the MAQ20 and it will continue to log data until it reaches the end of the log based on the parameters you have specified (number of samples, time interval, etc.)

What file/formats are supported/produced with ReDAQ Shape?
Data logged in the Analyze panel in ReDAQ Shape can be exported to a .txt file or Excel file. The SD Card Logger can generate .csv files as well.

Can SCM5B modules be hot swapped?
Not just SCM5B modules, but any signal conditioning module series and MAQ20 I/O modules can be hot swapped. A minimal amount of signal settling time may result, but there will be no damage to the device.

What type of SD card does the MAQ20-COMx module accept?
The MAQ20-COMx modules accept microSD cards of up to 8GB size.

How do I get custom channel names from ReDAQ Shape to show up in my SD card log?
Applying custom channel names in ReDAQ Shape is for display purposes on the Acquire panel only, it does not change any information within the module. Because the SD card log takes place within the MAQ20-COMx module, separate from the Acquire panel, it is not possible to have your custom channel names from the Acquire panel in your SD card log.

Can I use all features of the MAQ20 if I don't purchase a MAQ20-940 or MAQ20-941?
Yes, every function of the MAQ20 can be used as long as you have some way to communicate with the system via Modbus. ReDAQ Shape simply offers a more intuitive and user friendly approach to MAQ20.

Do MAQ20 modules automatically register in the system when plugging into the backplane?
Yes, any MAQ20 I/O module should automatically register in the system once plugged in. If you are finding that the module is plugged in and not registered, check the diagnostic LEDs on the module to verify that it is receiving proper power. These diagnostic LEDs can also be used to further diagnose any connection issues if the modules are still not registering. For more information, see the hardware manual of the corresponding module, which can be found in the MAQ20 section of our website.

Can the SD card logger in MAQ20 be used in IPEmotion?
SD card logger functionality has not been implemented in IPEmotion yet. Please contact Dataforth for more information.

Does the MAQ20 have capabilities for stand alone operation?
The SD Card Logger in the MAQ20 can function as a standalone data logger once configured. After initiating the log, the system can continue to log data for the rest of the configured data collection period even if it is disconnected from the host PC entirely. However, if you wish to configure another log, you must reconnect the system to the host PC. Any other logging processes with the MAQ20 require connection to the host PC for the entire logging period.

Can Developer unlock codes be used with the User version of ReDAQ Shape?
Each type of unlock code is only compatible with its respective software version and associated MAQ20-COM module HW. Developer unlock codes will only work with Developer version of ReDAQ Shape and User unlock codes will only work with User versions of ReDAQ Shape.

Will I run into any problems operating my MAQ20 system for 60 days straight?
No, we have many customers that use our MAQ20 system 24/7, 365 days a year. We also have a weather station onsite that uses a MAQ20 system continuously running 365 days of the year. Please visit to access the weather station demo.

Can ReDAQ Shape licenses be transferred between systems?
ReDAQ Shape licenses are tied to the COM module of the system, so no, they cannot be transferred. However, projects created with a Developer license can be ran on other systems with a User license.

I tried to print a test data sheet for my MAQ20 module on your website but I couldn’t. Is there anything special I need to do to get a test data sheet for my MAQ20 module?
MAQ20 test data sheets are not available on our website. However, test data sheets for purchased MAQ20 modules are available upon request. Please contact our Customer Service Team at

Is it possible to send a remote setpoint via Modbus/TCP to a PID loop running your ReDAQ Shape software on MAQ20 hardware?
Yes, it is possible to send a remote setpoint via Modbus/TCP to PID loop running in ReDAQ Shape by writing to the Modbus registers of the MAQ20 hardware. Please see the address map at the end of the MAQ20 PID Controller User Manual

Can I save the settings of my MAQ20 module to EEPROM outside of ReDAQ Shape?
Yes, refer to the address map of the module you are using which can be found at the end of that module's hardware user manual. There will be a register "Save to EEPROM." Writing the appropriate value as described in the address map to this register will save your module's current settings to EEPROM.

Is there a demo version available for ReDAQ Shape?
Yes, the version available for download from our website can serve as a demo if you do not have an unlock code. The unlicensed software will run for 30 minutes with full functionality with no license. Once the 30 minutes is up, you can restart the program to reset the 30 minute time for as many times as you would like.

Does USB have a faster response time than Ethernet when communicating with the MAQ20?
The MAQ20 ideally has equally fast response times regardless of whether you use USB or Ethernet connection. Other variables outside of the MAQ20 can influence this response time however, such as if you are using a USB to Ethernet adapter or if the MAQ20 is part of a larger company network.

How does the load resistance of a module affect the noise at the output?
Noise at the output of a module is independent of load resistance.

Can I still export my acquired data to a text file or Excel spreadsheet with the User version of ReDAQ Shape?
Yes, these options are available in both the User and Developer versions of ReDAQ Shape.

Can I copy and paste data from ReDAQ Shape while in acquisition?
Yes, ReDAQ Shape has the ability to directly copy and paste raw data from the "Analyze" tab, without interrupting the acquisition process. However, you must use the "Copy To Clipboard" button located at the top left corner of the raw data table - using keyboard commands or right clicking and selecting "Copy" will not work.

Is there any way to select or use a custom port or transmission method other than port 502 with the MAQ20-COMx?
Currently, ports are not selectable in the MAQ20-COMx modules and they only work with port 502. This may change in a future firmware update.

Why am I seeing an "Unhandled Exception: Invalid Input String" error when I click on my MAQ20-COMx module in ReDAQ Shape?
This usually has to do with the display language of the host PC being set to a language other than US English. If you are experiencing this error, please try setting the display language of your PC to "English (United States)" and then see if you are still experiencing issues. If this does not fix the problem, please contact Dataforth technical support.
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