Previous runs of dev_acquisition_start() keep the enabled_channels list
populated if they fail. This means that once an invalid channel
configuration was detected, it will be detected again even if the channel
configuration was changed. With this change, the list will be cleared
before being populated so that any stale entries are removed.
The Brymen BM25x series supports the BC-20X that is an opto-isolated
serial cable. The link seems to be unidirectional i.e. when activated
the DMM periodically sends updates to the host while the host cannot
control the DMM in any way.
The protocol is documented in "6000-count-digital-multimeters-r1.pdf"
that is available from the manufacturer. Every 15 byte packet consists
of a bitmap where the bits correspond to segments or symbols on the
LCD display i.e. the DMM essentially sends the contents of its screen
to the host in every update. This driver then decodes the measured
quantity, unit and its value from the bitmap.
Marcus Comstedt
Soeren Apel
Bert Vermeulen
Janne Huttunen