Green PWR LED is permanently off


Verify that:

  • The product is connected to an active USB port.

Green PWR LED is on but the product is not working


Make sure that the drivers for CMa30 are correctly installed (Windows):

  1. Select Start.

  2. Right click on Computer and select Properties.

  3. Select Device manager.

  4. Expand the tab under Ports (COM & LPT).

  5. Check if there is a port called ”Silicon Labs CP210X USB to UART Bridge”. The line ends with the COM port the device has been assigned.

  6. To ensure which port is used, the USB cable should be plugged out. The port will then disappear from the list. When reconnecting the USB cable the port appears in the list again.

  7. If the device is not found in the list, the drivers for the device need to be installed/reinstalled. Download the drivers on CMa30 Drivers.


Steps 1-3 may look different depending on which version of Windows you are using. The keyboard shortcut Windows key + R with the command devmgmt.msc can also be used to start the device manager (press the Windows key and R simultaneously and type devmgmt.msc in the box that appears).

The product works but no slaves are found


Verify that:

  • The yellow TX LED is flashing when the scan is started from the M-Bus software. This is a confirmation that the correct COM port is selected.

  • Scanning/reading is made with the correct baud rate.

Check if:

  • The red ERR LED is flashing. This indicates error on the bus.

  • The red ERR LED is permanently on. This indicates short circuit or overload of the bus (more than 30 M-Bus loads).

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