I've got a battery management unit that is reluctant to
demonstrate functionality. The vendor's terminal com
software seems non-functional (will not install).

So far the only evidence of life is a control line (one
of three) hard on, and rare /XFFE /FFF signalled outputs
on the rs232 port. Internal DC-DC fails to power LEM
sensor. Balancing terminals seem inactive.

Can anyone recommend a tutorial on poking a serial port
for status / data register contents ?

It should be reporting on the voltage of four LiFePO4 batteries,
powering a LEM sensor and reporting current. Many other
undocumented features for I/O via remote terminal. Has
CAN port, which seems to be used only for control power and
crude 'run' (input) /'stop charging' (output) LF/DC signals.

I'm in touch with the overseas vendor, but they seem reluctant
to comment on their SW functionality or test criteria for the
unit. Outgoing photographs and diagrams from here, mostly, so far.
The manual and it's diagrams don't make much sense, refering
to non-existent hardware or unavailable interface modules.

Someone has gone to a great deal of trouble to chart the
identity, labelling and function of I/O terminals, but these
are largely ignored in subsequent diagrams or instructions.

Mostly used in SE Asia or the Indian subcontinent. English
version is only recently available.

RL