Hi everyone,
I've pushed a first, very simple and work-in-progress version of the
generic "transforms" framework we wanted to have in libsigrok for quite
a while now (and the respective sigrok-cli support for it).
A "transform" is basically something that takes one packet (analog or
digital or other) and outputs a packet (or NULL, i.e. no packet).
A few simple ones are implemented for now:
- nop: Do nothing; take the packet, output it again unmodified.
- scale: For every analog packet it gets it will scale (multiply) the analog
(float) value by a specified factor. Any packets other than analog
ones are ignored and passed on unmodified.
- invert:
- For analog packets: outputs the same packet, but analog values x
are changed to 1/x.
- For logic packets: Every 0 probe becomes 1 (and vice versa).
There are *many* further transform modules that can be written and
should prove highly useful, e.g. "add", "subtract", "multiply", "divide",
"average", "adc", "dac", "downsample", "upsample", and lots more.
I'm currently in the process of writing a few more, e.g. "adc" which
will convert an analog channel to a digital one (using a "threshold"
option that specifies which analog values are to be considered "high"
and "low").
Implementations for other modules and ideas for useful ones we should
consider adding are welcome!
Here's a few examples of what is currently possible with this initial
draft version:
$ sigrok-cli -d demo:analog_channels=1:logic_channels=0 --samples 2 -T nop
A0: -25.000000 V
A0: -25.000000 V
A0: 0.000000 V
$ sigrok-cli -d demo:analog_channels=1:logic_channels=0 --samples 2 -T
scale:factor=3.5
A0: -87.500000 V
A0: -87.500000 V
A0: 0.000000 V
$ sigrok-cli -d demo:analog_channels=1:logic_channels=0 --samples 2 -T invert
A0: -0.040000 V
A0: -0.040000 V
A0: inf V
$ sigrok-cli -d demo:analog_channels=0:logic_channels=1 --samples 192 -T nop
D0:10001111 00001111 10001111 00001111 10001111 01110111 11111111 00111111
D0:10001111 00001111 10001111 00001111 10001111 01110111 11111111 00111111
D0:10001111 00001111 10001111 00001111 10001111 01110111 11111111 00111111
$ sigrok-cli -d demo:analog_channels=0:logic_channels=1 --samples 192 -T
invert
D0:01110000 11110000 01110000 11110000 01110000 10001000 00000000 11000000
D0:01110000 11110000 01110000 11110000 01110000 10001000 00000000 11000000
D0:01110000 11110000 01110000 11110000 01110000 10001000 00000000 11000000
There are *many* missing features, as well as various design and
implementation problems and bugs. Please don't consider this as a
finished feature yet, it's more of a preview of where we're aiming at
with this; lots more work is required to make it all useful.
Any reviews, comments, suggestions are highly welcome of course.
Here's a short and incomplete list of TODOs and issues:
- Most modules will need a "channels" option to specify on which
channel(s) they should operate. Currently they're all hardcoded to
affect all channels.
- (C++) bindings need to gain support for this (e.g. to make this feature
available to frontends like PulseView and sigrok-meter).
- Various design/technical issues need to be sorted out, e.g. who frees
what and when; how to let frontends know that a transform is
generating a "new channel" that has nothing to do with any physical
channel that may have been present on original device, etc. etc.
- Currently multiple transforms can be chained linearly; later on we'll
likely want some "pipes-and-filters"-style, "flowgraph" based system
with more flexible facilities.
- Options may need some more metadata, e.g. frontends may need to know
which options are required or optional, which ranges of values are
allowed etc. etc.
- lots more...
Uwe.
--
http://hermann-uwe.de | http://randomprojects.org | http://sigrok.org
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