DeviceNet supports so called explicit messaging. The purpose is to read or write a single attribute value from a DeviceNet device.
In this particular case we read the DeviceNet power supply voltage at a device locally. It could be that the power supply voltage is at a critical low value in a certain segment of the DeviceNet network. With a too low power supply voltage devices could malfunction.
Every Omron DRT2 DeviceNet device however can measure the local power supply voltage locally and the value can be read over DeviceNet from the device via an explicit message.
The attached example code reads this power supply voltage value from a DeviceNet device. Further evaluation can be done in the PLC or SCADA.