No communication on the EIB Bus and the 'Collision' warning is set to 1 on the FBox!

FAQ #101093

 

Symptom
If the cycle time is bigger than 100ms and a load on the network is heavy, the driver has difficulties to communicate with a BCU1 coupler. This can have the following effects: 

• RCV-Timeout errors are displayed
• Cycle time warning are displayed
• The number of 'Collision' warning is high
• Loss of reception telegrams. Values are not always correctly updated. 

Reason
The BCU1 coupler does require the PCD to receive the telegrams byte by byte. In case the CPU has a cycle time of 100 ms or higher and a high EIB bus load is present, the PCD can no longer properly receive every telegram.

Solutions
There are two possibilities.

1. The recommended one is to use a BCU2 coupler (using the FT1.2 protocol). This kind of coupler does transmit telegram by telegram and communicates at a higher baud rate with the PCD. This way every telegram transmitted on the EIB bus can be transferred to the PCD.
2. Alternatively the FBox driver can be configured in a way that it reads more frequently from the BCU1 coupler. Please note that there can still be telegrams lost because the BCU1 coupler can not transmit as many telegrams as the EIB bus itself can transmit! If a BCU2 coupler is used, the transmission speed between the PCD and the coupler is higher than on the EIB bus, and as a result all telegrams can be transmitted even also on a loaded EIB bus.

For reading more frequently from a BCU1 coupler, please follow the steps below:

• Use the latest EIB Driver FBox library (in every case version $2.5.032 or later).
• Configure the EIB Driver to use an XOB interrupt, for that this cyclic XOB is used for reading the characters from the BCU coupler in a fix time interval of 10 ms.
  This allows to improve greatly the reaction time of the driver.
    

Remark
For new projects the FT1.2 is strongly recommended in every case!