Mixed module versions results in "missing modules" if order is incorrect

[mitchese]

This may be more of an issue for documentation update or possibly an unsupported configuration, but I found this issue odd.

I have a pack with mixed modules, mixing between 4.21 and 4.40. All modules are flashed with the current master version (0af6c8d).

If I connect them

Controller TX --> 4.40 --> 4.21 -> 4.21 -> 4.40 -> 4.40 -> Controller RX

then the controller shows I only have 4 cells. The "first" (4.40) module is missing in the delivered values.

If I re-arrange the same modules to the following configuration:

Controller TX --> 4.21 --> 4.21 -> 4.40 -> 4.40 -> 4.40 -> Controller RX

then all modules report correctly. It appears that when communicating between different module hardware versions, if a newer module transmits to an older one, then this is ignored/dropped

Not a serious issue, as I just re-arranged the modules that I have so the older ones are first in the string.