Dear Wizards,

I am in the process of setting up a RPi-based automatic read of a set of electrical meters. The meters (8 single-phase SDM120's, and 4 triple-phase SDM630's) are all on a single modbus line, and I can connect to the meters both using python/minimalmodbus and with collectd/modbus.

If possible, I believe it preferable to use a well-tested software package like collectd, rather than basing on my own implementation. However, I seem to have stuck two points, which could be problematic in my particular case:

A: The meters (SDM120 vs SDM630) do not support the same (maximum) baud rates. They max out at 9600 baud and 38400 baud, respectively. If I have to, then I could run the entire line @9600 baud, but since the SDM630s contain a lot more information/registers, I think it might be beneficial to connect at max baud rate to these devices.

Q: Can I use devices with different baud rate on the same line with collectd/modbus? They have to share localhost, device /dev/ttyUSB0.

Further, I would like to read a few parameters (like instantaneous power [W]) very frequently (to be able to store eg max per hour/day), while other metrics are needed only rarely.

Q: Is it possible to set "Interval" on a per-metric ("Collect") base, or must all Slaves/Data [types]share a single "global" value specified on a per<Host>-basis?

Many thanks for a fantastic project,

Bjarne Büchamann

PS: Eventually, the measurements will be sent to an MQTT-server, but that is a different story.

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