Adding devices to the device list

Purpose​

This article helps you understand how the EMH works to assist you with your programming of the device. This article does not cover configuration of LAN settings to enable Modbus TCP or BACnet IP as a basis for enabling BACnet IP communications.

How does automatic Modbus RS485 device detection work?​

The EMH device list will automatically display devices detected on the Modbus RS485 daisy chain. This depends on several factors:

• The device is configured with a unique Modbus ID#.
• The device is programmed with RS485 serial settings that match the EMH.
• The RS485 timeout in the EMH is set sufficiently to wait for a response from the device.

How fast does Modbus RS485 auto-detection work?​

In factory configuration units, the default auto-detection time will normally pick up a newly available device within 1 minute. Note that data logging of devices on the Device List takes precedence over scanning, so extend your waiting estimates accordingly.

To estimate auto-detection time, use the following formula based on your EMH's RS485 settings:
255×nBauds×nParity×nStopBit×secTimeout , where each n item is the number of enabled options. The resulting number is the number of seconds for the autodetect process. Multiply the end result by 2 if you are using the EMHXD model.

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How do I bring in Modbus TCP or BACnet IP Devices?​

For security, the EMH does not auto-scan the LAN to locate Ethernet-connected devices. Manual entry of the device's configured IP/Object ID/Port is required. A logged-in user may run a BACnet IP network scan as needed to locate devices and available datapoints. The EMHXD model includes a Modbus TCP device discovery feature to also assist with adding/locating devices.

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Optimizing Timeout Settings​

While a quick timeout helps with faster auto-detections, leaving the short default at the HUB or at each ModHopper (if your site is using them) can cause the logger to not see a device even though it is programmed correctly and is responding to the unit's request. Set the timeout just long enough plus some margin for optimal performance.​

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Most devices will respond within 200ms, but for higher compatibility, set it to 500ms on initial setup. When using ModHoppers, start with 1.5 seconds and increase if you're missing devices.​

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On your Device List, there is a "Stats" radio button that allows you to view the RTT of each device. This is a great tool to help you with optimizing the timeout setting.​

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ModHopper Considerations​

The ModHoppers have their own timeouts that can be set; the default is 240ms, but 500ms makes it the most compatible. They also auto-detect devices attached to them, which must happen first before the EMH can detect them.​

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To modify the ModHopper's timeout, you will need go into each ModHopper listed on the Device List, click into the device, then click the configure button, then the advanced button. Change the local RS485 timeout setting, then "Save Advanced".​

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Use the same formula to calculate the ModHopper auto-detection time, then add that to the EMH detection time to know the total time.​

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Signal Strength and Hops​

Additionally, consider ModHopper signal strength and the number of hops. This information is best reviewed in the EMH's web interface under Wireless > ModHoppers.​

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Ensure at least 30% or greater signal quality for successful deployment.​

For each additional hop, factor in an additional 500ms of timeout.​

Why is a device appearing as unconfigured or unknown status?​

• Unconfigured: This status appears when a Modbus RS485 connected device is automatically detected. Simply name the device to complete setup; its status will change to OK.
• Unknown: This status means a device responded to the EMH on a given ID# but the firmware cannot match it to a known built-in driver.

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Steps to Handle Unknown Devices​

1. For devices with the same mapping as a built-in driver:
   • Add the device and select the device type from the drop-down menu.
     • If you get an error 192 code, install gen3 HUB firmware v02.23.0123 or gen4 firmware v04.24.0226 or later.
     • Go to the Device List, click into the device, then click the configure button, then the advanced button.
     • Turn on "Skip verifying device class" and click "Save Advanced".
     • Wait for another log interval or reboot the HUB to clear the issue.
2. For devices without a built-in datapoint mappings:
   • Use a device template mapping to read the device. Create mappings manually using the on-board template editor on the web interface.
   • Mappings can be saved to your PC, transfer to other PCs, and upload into other EMHs.
   • Check the communities forum or contact tech support for available 3rd party mappings or to submit ones you have created to share.

Why am I not automatically seeing my device appear even though I've confirmed everything?​

For devices that do not automatically appear, re-verify the comms settings on all ends. If a device is readable but did not respond to the auto-detection algorithm, manually adding the device is necessary. For ModHoppers, pre-adding devices to the Device List may be more efficient.