Why do some M-Bus devices not work on all ports of a PCD2.M5 or a PCD3?

FAQ #101382

 

Symptom
Some M-Bus devices connected to a PCD2.F2xxx or a PCD3.F2xx (or on the ports listed below under "Remark") are not answering to all requests. The same device does work fine when the M-Bus gateway is connected to another port (e.g. on port 0 of the PCD2.M5). 

Reason
The reason for this phenomenon could be that the M-Bus device is very sensitive against inter-character delays in the telegrams.

Solution
In order to avoid the inter-character delays a new feature has been implemented in the firmware of the PCD (the freeze bit, see FAQ 100916). The M-Bus library 2.5.203 from Engiby does work with this mechanism and thus avoids the inter-character delays in the telegrams.

Remark
With firmware 1.10.16 it has been observed that such inter-character delays are present in telegrams sent on the ports listed below even when using the freeze-mode mentioned:

• PCD2.M5xxx: port 2 and port 3
• PCD3.Mxxxx: port 0 and port 3

In order to avoid these inter-character delays, please use firmware 1.10.51 for your PCD2.M5xx0 or PCD3. This firmware can be downloaded from the according product section on the support site www.sbc-support.ch.