How to Connect the Davicom ACPM-1 (WattNode Pulse) to the Cortex

There are three main steps when connecting an ACPM-1 to the Cortex:

1- Serial protocol configuration

2- Modbus protocol configuration

3- I/O configuration

These three steps are separated into the three first main sections of this article for easier access and comprehension.

Serial protocol configuration (RS-485)

USB dongle

1- Before starting the setup, make sure you have on hands an USB-to-RS485 serial adapter (or dongle), like the USB-RS485-WE-1800-BT from FTDI Inc. shown in the image below. Comlab, as well as most popular electronic components distributors like Digi-Key, Mouser, Newark, etc… carry this dongle.

An USB-to-RS485 pigtail serial adapter is required to connect an ACPM-1 to a Cortex.

2- Along AC voltages, if you plan on measuring AC currents, special AC current transformers will be required (1 per phase). Comlab carries these transformers, as seen in the image below, which product datasheet is available here.

Available current transformers for the ACPM-1.

3- Having a copy of the Cortex Mega Workspace will greatly facilitate the display of the different ACMP-1 measurements in a Cortex screen. Please visit Davicom’s website under Support > Resources > TechTips, Notes, Apps and more where it can be found, or contact Davicom technical support.

The screenshot below shows the MEXM/Modbus tab view of the Cortex Mega Workspace. Since the Davicom MEXM expansion panels use Modbus, the same workspace can be used for Modbus accessory, like the ACPM-1 for example (note that only the Metering Inputs boxes would be used for the ACPM-1). The Cortex workspaces can easily be edited to suit your needs. Please contact Davicom technical support for information on how to edit a workspace.

View of the Cortex MEXM/Modbus workspace tab.

4- Quick test setup

To ease the setup procedure listed in this guide, a powered setup was used. As much as possible, we strongly suggest you to also use a powered setup. Again, be very careful of possible lethal voltages and currents when setting-up and using an ACPM-1.

In order to set an ACMP-1 on a Cortex, it is required to have the ACPM-1 connected to the Cortex and have it powered. The image below shows an example (using a 208 VAC version of the ACPM-1) of how to quickly and easily power-up an ACPM-1. At this time, only power is required for the ACPM-1, no need to have any current draw. For current draw, any 120 VAC load would do, like a portable household heater for example.

If you want to test the ACPM-1 with a current draw, a current transformer is required, along a small splitted AC power cord extension (see note below).

This setup will not only verify that everything is working ok before heading out at a site for the installation, but it would also allow to get familiar and acquainted with the ACPM-1 along the Cortex.

NOTE: One of the sides of the AC current transformers made for the ACPM-1 can be opened to insert a wire without having to cut it.

Example of a quick test setup to verify the ACMP-1 and get acquainted with it.

5- Setting up the ACPM-1 Modbus RTU address and Modbus comm speed.

The image below shows the default factory-set DIP switch that is found on the top of the ACPM-1. Make sure it is set identically as shown, which is switch #1 and switch #8 set to “ON”, and set all the other switches to “OFF”. This sets the ACPM-1 with an RTU address at 1 and a communication speed of 19200 bps.

ACPM-1 top DIP switch to set the unit’s Modbus RTU address and Modbus communication speed.

6- Connect the USB-RS485 serial adapter on the ACPM-1 as shown in the image below.

Wiring of the USB dongle on the ACPM-1.

7- Setting up the USB-RS485 serial adapter parameters in the Cortex.

Connect the USB-RS485 adapter into one of the 4 Cortex rear USB ports.

Connect to the Cortex using a web browser or DavLink.

When connected, from the top menu, go to Devices > USB Serial.

The screen shown below will appear, showing the detected USB-RS485 serial adapter.

Right-click on the green 1USBS1 ID, or anywhere on the line, and click on Config.

8- The following screen will appear. In the Active Default and Normal Default description boxes, write something like ACPM-1 USB-RS485. Next, click on the Actions tab.

9- In the new screen that opens, set Usage to Modbus, set Baud Rate to 19200, and click on save. This completes the setup of the USB-to-RS485 serial adapter.

Serial port

Please refer to Section 1 of this article for information on hardware configuration. Section 2 explains how to configure the software for any device, but we will explain how to configure the software for the ACPM-1 specifically below.

1- Go to the Devices drop-down menu.

2- Go to Modem & IOIOI.

3- Select IOIOI and click the configuration button.

4- Enter ACPM-1 for the Default Description.

5-Select Modbus for the device Usage.

6- Select 19200 for the Baud Rate.

7- Leave the Flow Control at NONE.

8- Save the configuration.

9- Exit the configuration screen.

Modbus protocol configuration (RS-485)

ACPM-1 Custom Register Map

For more information on Modbus configuration and operation, please refer to this article. (currently unavailable)

The table below shows the ACPM-1 Custom Register Map. You will need this data for the configuration. If you wish to be able to consult it without having to scroll back up every time, you can click here to open the table in a new tab.

* The CurrentA, CurrentB, and CurrentC Integer value listed in the chart is for current transformers rated at 50 Amps. If you are using current transformers rated at a different current value, use the corresponding Integer value from the list below:

  • For current transformers rated at 50 Amps, use a value of 0.0025
  • For current transformers rated at 100 Amps, use a value of 0.005
  • For current transformers rated at 250 Amps, use a value of 0.0125
  • For current transformers rated at 1000 Amps, use a value of 0.05
  • For current transformers rated at 1500 Amps, use a value of 0.075

If your application requires to monitor only one or two phases, or only measuring AC voltage, a shorter range of registers can be used.

Adding and configuring a Modbus device

1- In the Cortex menu, go to Devices > Modbus, and click on the + (Add) button.

2- In the next screen, write ACPM-1 in both the Default Active and Default Normal boxes. Click on the Save button and don’t close the screen.

3- Click on the Parameters tab and set the screen settings as per the ones shown in the image below.

4- Click on Comm Lost to expand its menu, and uncheck the Pause On.

5- When done, click on the Save icon and close the screen.

If you click on Details to expand it, you will see this section appear:

This shows you the corresponding ID for each register address. This will be important once configuring the metering inputs.

NOTE: Communication is still not fully established between the ACPM-1 module and the Cortex 360. In order to establish full communication, it is required to configure at least one metering input. In other words, COMM LOSS and COMM RESUME notification will not work unless a metering input has already been configured.

I/O configuration (RS-485)

Now that the Modbus device has been properly configured, we can set and enable the associated Modbus Metering Inputs.

1- In the Cortex menu, go to Inputs > Metering Inputs, then in the screen that opens, click on the + (Add) button.

2- In the next screen, click on the input’s ID drop-down menu and select the first Modbus Metering Input listed, 1MA1.

Several other Modbus Inputs are now visible in the list, confirming that previous settings have been properly made. The quantity of Modbus Inputs listed matches the Length number set in the configuration screen seen at step 3 of the previous section. These Inputs are the ones that were listed at the end of the previous section.

3- In the next screen, enter description such as Phase A Power (Watts).

In this example, the description corresponds to the first Modbus register of the Custom Register Map seen in Section 2.1, which is register number 43478 (also set at step 3 of the previous section as the register Start Address).

4- When done, click on the Save button, then click on the Actions tab.

5- The following screen appears, which is the default Metering Input configuration screen, this one being for the first Modbus input, the 1MA1.

Note that both the standard Metering Inputs and the Modbus Metering Inputs share the same identical configuration screen menu (other than the RAW option, which is only available for Modbus inputs)

6- In the configuration screen, set the Voltage Range to RAW, and set the Measurement Unit to W.

Note also that at this moment, for this input, the B value of the Sensor Coefficients section is left to the default value of 1 as per the listings given in the register map in Section 2.1, but a value of 0.1 would have to be used for other measurements, like when reading RMS voltages for example. Other values can also be required.

7- Click on the save button, and close this screen only.

8- In the window left open, as seen below, the power consumption appears.

9- You can now close this screen.

10- Looking at the workspace will also show proper measurement of Modbus Metering Input #1, 1MA1.

11- The other Modbus inputs can now be added and configured using the same procedure as described in the steps above.

Once fully configured, the screen should look something like this:

Basic description of the ACPM-1 top LED indicators

The COM LED shows the status of the Modbus communication between the ACPM-1 and the Cortex.


  • Off = No communication.
  • Blinking = Communication is ok.


  • Blinking = Communication problems.

The STATUS LEDs show the status of each of the three current measuring inputs of the ACPM-1.


  • Solid on (no blinking) = No current is flowing through the transformer
  • Blinking = Current is flowing through the transformer in proper direction


  • Blinking = Current is flowing through the transformer in reverse direction

To correct an improper direction of current flow:

  • Remove the transformer side insert
  • Remove wire
  • Twist transformer 180° (front-to-rear)
  • Replace wire
  • Replace the transformer side insert

Please consult the Wattnode Installation and Operation Manual for a complete listing of the LED indications.

Was this article helpful?
Dislike 0
Views: 583

Leave a Reply