Negative values start with F about libmbus

[trsqr]

Absolutely.

[lategoodbye]

@trsqr Thanks for your report. Is it okay for you to let us integrate the M-Bus telegram in libmbus test data?

[lategoodbye]

Today i had some time to look into this. At first the behavior of mbus-tcp-request-data is expected, because most of the examples uses the non-normalized output which is dedicated for humans (like M-Bus in general). Since this commit 2f9fa5c the libmbus is able to handle F as a negative value.

So your next question would be like: why doesn't mbus-tcp-request-data use this feature?
Answer: it's not that simple. Unfortunately all the other hex values A-E are also valid values, so simply enabling this for every BCD value would break error values. So it's very hard for a machine to decided how to decode.

A possible hack could be to handle "Value during error state" as hex value and the other one as integer.

[lategoodbye]

The hack is available as PR #197