Add a protocol decoder for the Cyrustek ES51919 LCR meter chip.
This chipset (together with ES51920 front-end) is supposedly used
by multiple different portable LCR meters including at least
DER EE DE-5000, Yihua V&A VA520, Mastech MS5308, Uni-T UT612,
CEM DT-9935 and various OEM rebadges of them.
The communication protocol seems to be implemented on the Cyrustek
chip itself so all the different models are expected to use the
same protocol if they implement a host connection. Unfortunately
the protocol is not available in the public documentation of the
chipset, so this implementation is based on reverse engineering it
from traffic captures.
The actual connection between the meter and the host computer may be
different from meter to meter even when based on the same chip. This
module implements a decoder for the protocol and some common helper
functions for interfacing with the meter via an RS-232 serial port.
This calculates a proper timeout value for blocking writes on the
given serial port, for the given number of bytes. Timeout is based
on a fixed 10ms OS overhead, baud rate, data bits and stop bits.
Set this new parameter to 0 (no timeout) at every call site. This is
consistent with previous behaviour, so cannot cause any regressions.
Waiting forever for a serial operation is clearly always wrong. Without
specific knowledge of each device and driver however, I can't choose
appropriate timeouts for each call. The maintainers of these drivers
will need to do so, and also add appropriate handling of timeouts.
When this commit is merged, a bug should be entered for each driver
that is touched by it.
This signifies to the module instance no more input will come. This
will cause the module to process any data it may have buffered. The
SR_DF_END packet will also typically be sent at this time.
When an input module instance has received enough input to fully
populate the struct sr_dev_inst, sdi_ready is set to TRUE and its
receive() method returns immediately. Any remaining received data
is buffered until the next time the function is called.
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.
Janne Huttunen
Aurelien Jacobs
Bert Vermeulen
Martin Ling
Soeren Apel
Uwe Hermann