Waveform

When using oscilloscope you can download waveform for any given channel by calling channel.get_waveform() method. On this page we will outline what you can do with the waveform object.

Accessing x-y values

Functions Waveform::x(...), Waveform::x(...) and Waveform::xy(...) are used to access x-y values of the waveform. Function xy(...) is a superset of the other two. Hence, we will talk just about this function. The same concepts will be applicable to the x(...) and y(...) functions.

By default, simply calling waveform.xy() return tuple of numpy ndarrays for the whole of the trace. First one holding x-axis values in unit of seconds and second y-axis values (usually that is voltage).

ts, ys = waveform.xy()

You can request different time units on the x-axis. For example in microseconds:

ts, ys = waveform.xy("us")

or

from inctrl import TimeUnit

ts, ys = waveform.xy(TimeUnit.US)

You can indicate time unit as either a string using usual unit notation ("s" for seconds, "ms" for milliseconds and so on) or pass TimeUnit enum value.

Time 0 corresponds to the moment of when trigger is fired. To see part of the waveform after the trigger you can pass x_predicate filter argument like so:

ts, ys = waveform.xy(x_predicate = lambda t: t >= 0)

Note that x_predicate function will always receive time in seconds, independently of the requested time unit. Thus following two calls return the same arrays.

ts, ys = waveform.xy(time_unit = TimeUnit.US, x_predicate = lambda t: t >= 0.003)

ts, ys = waveform.xy(time_unit = TimeUnit.MS, x_predicate = lambda t: t >= 0.003)

Math operations

Scaling

Waveform can be multiplied or divided by a number producing new scaled waveform. For example:

w2 = waveform * 2

w_half = waveform / 2

Add, subtract, multiply

Two waveforms that have exactly the same values on the x-axis can be added, subtracted or multiplied.

waveform1 * waveform2

Changing waveform metadata

Some of the waveform metadata can be changed. In particular waveform has a name derived from either a channel name or when waveform if obtained by calling channel.get_waveform(name = "$name"). This name is used for plotting waveform.

You can change it like so

waveform.name = "Vout"

Saving into a file

Waveform can be saved into a file together with all of its metadata like so

waveform.save_to_file("waveform.wfm")

This will save it in compact binary form using parquet data format.

It can then be loaded like so

waveform = Waveform.load_from_file("waveform.wfm")

Exporting into csv

X and Y values for a waveform can be exported into a csv file like so

waveform.export_to_csv_file("waveform.csv")

In this format no metadata will be stored in the resulting file, online time and voltage values. By default, resulting csv file will include a header (first row) identifying column names, these will be strings "t" and "y". This header can be excluded like so

waveform.export_to_csv_file("waveform.csv", include_column_names = False)

Time column will be in seconds but can overridden like so

waveform.export_to_csv_file("waveform.csv", time_unit = "us", include_column_names = False)

or

waveform.export_to_csv_file("waveform.csv", time_unit = TimeUnit.US, include_column_names = False)

Plotting

If optional matplotlib library is installed then waveform can be plotted and shown in GUI window like so

waveform.plot()

This call will block until plot window is closed, unless optional block argument is set to False

waveform.plot(block = False)

By default, time unit on the x-axis will be set automatically to provide most compact representation for time values. It can, however, be overridden like so:

waveform.plot(time_unit = "ms")

waveform.plot(time_unit = TimeUnit.MS)

To generate image png file, pass to_file argument like so

waveform.plot(to_file = "waveform.png")

When called like so this call never blocks independently value assigned to block argument.

Writing into png file will use default DPI (dots per inch) value as set in matplotlib, but can be overridden by supplying dpi argument like so:

waveform.plot(to_file = "waveform.png", dpi = 600)

Note, that DPI value will affect image size.