Velbus protocol : what about message collision?

For developers
1

Hi Velbus team,
I would to know if VMB1USB is able to manage message’s collision.

If I send a message on the bus through VMB1USB, if a message is already on the bus (coming from a VMB4PD ou VMB1TS for example), is the VMB1USB able to delay it emission or is my message lost ?

I ask this because I thinking about 2 ways to use the BUS :

  1. My apps send a message and no feedback needed (but I’ve to be sure that my message is arrived to it destination)
  2. My apps send a message and have to wait for a feedback (but which one ? LED blinking ? module status ? etc.)

if nothing happens, should I re-send the message ? what is the timeout (I think about 3 seconds) ?

Thanks for your answers,
David

2

When sending you need a delay of 60ms between each packet (to prevent flooding the VMB1USB). The internal protocol of the modules handles collisions by adding a delay and resending, so your message will not be lost. VelbusLink assumes an answer should be received within 3-5 seconds.