Flashing lights on USB interface

Got the USB wired up and the power light is on.
plug in the USB cable and the two yellow lights start blinking back and forth quite rapidly… Manual says too high USB power consumption, but don’t say why or what to do about it !!!

Power unit is putting out 20 volts, but Velleman say that is normal and not and issue.

Help !


Hi Andrew,

LD1 (red led) should be on continuously
LD2 and LD3 (yellow leds) should be blinking alternately
LD4 should light up whenever there is traffic on the bus

So, assuming you installed the driver and from what you are saying, everything is working as it should!

Next you should verify if a COM port has been added to your list of ports. You can do this by opening the Device Manager (Start -> Run -> devmgmt.msc -> OK) and checking if a port appears or disappears under the “Ports (COM & LPT)” tree when you plug/unplug the Velbus.

Yup, i get the port opening when the USB interface is plunged in, but it takes a different port ID each time, either Com3 & 4 or 5.

So i will need to write routine to discover the port.
Is there a way to address the port directly as a test, i.e. it’s own address that would confirm if it exists on the PC ?


Normally, the port numbers are remembered for each USB slot. If you plug it into the same slot each time, you should get the same port number each time. Serial ports are only identified by their name, eg. COM1, COM2, …

There is a way to detect all Velbus USB interfaces but this method requires some rather advanced programming.

Yes when i plug into the same port it recalls the same port address each time. Thank you for that.

Do you have an example of the program to detect the port, as if i write this program for other people to use, (which i may) i would need to consider several different setup configurations.

Thank you for your help.


I would recommend you create a configuration file in which you can specify a COM port or to open a connection dialog when your application starts. You can get the available ports from the Device Manager.

Enumerating all VMB1USB devices on the system is very complex, thus if I were you I would try all other possibilities first :slight_smile:

It involves calling SetupDiGetClassDevs from the Windows SetupAPI and then enumerating every device interface until you get a device with the same VID and PID of the VMB1USB.

GUID: A5DCBF10-6530-11D2-901F-00C04FB951ED
VID: 0x10cf
PID: 0x0b1b