There is currently no way to uniquely identify USB devices in
libsigrok. It uses the "bus.address" scheme which is only
constant as long as the device remains attached to the bus.
In order to allow USB device persistence in PulseView, devices
need to provide a unique identifier even in absence of a
serial number. This function is the first step as it provides
the ability to query the physical location of a USB device.
SR_OK: a match was found.
SR_ERR: no match.
SR_ERR_DATA: a match was found but the module cannot handle the input.
SR_OK_CONTINUE: some module didn't have enough data to be sure.
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.
Bert Vermeulen
Martin Ling
Soeren Apel
Uwe Hermann
Janne Huttunen