Channels#

Channel module.

Contains the BaseChanProxy and AO/DOChanProxy classes representing individual channels.

class nistreamer.channel.BaseChanProxy(_streamer, _card_max_name, nickname=None)[source]#

Bases: ABC

The base of channel proxy classes.

abstract property chan_name: str#: Physical channel name.

property nickname: str#

Human-readable channel name used in visualizations.

Nickname is set when channel is added to the card. If no nickname was specified, chan_name() is used instead.

abstract property dflt_val#: The default value for intervals that are not covered by instructions.

abstract property rst_val#: The value set by add_reset_instr() command.

add_instr(func, t, dur, keep_val=False)[source]#

Add a finite-duration instruction.

Parameters:

func – waveform function instance
t (float) – start time
dur (float) – duration
keep_val (Optional[bool]) – determines the constant value after instruction end. If True, the last waveform value is kept, otherwise channel goes to default.

Return type:

float

Returns:

Instruction duration

Raises:

ValueError – if this instruction collides with an existing one
TypeError – if waveform function does not mach channel type (analog/digital)

Examples

>>> from nistreamer import NIStreamer, std_fn_lib
>>>
>>> strmr = NIStreamer()
>>> ao_card = strmr.add_ao_card(max_name='Dev1', samp_rate=1e6)
>>> ao_0 = ao_card.add_chan(chan_idx=0)
>>>
>>> ao_0.add_instr(
>>>     func=std_fn_lib.LinFn(slope=1, offs=2),
>>>     t=1.0,
>>>     dur=2.0,
>>>     keep_val=True
>>> )

add_gothis_instr(func, t)[source]#

Add an instruction with unspecified duration.

A so-called “go-this” instruction. During compilation, it will automatically fill the full interval until the next instruction start or global sequence end.

Parameters:

func – waveform function instance
t – start time

Returns:

Instruction duration

Raises:

ValueError – if this instruction collides with an existing one
TypeError – if waveform function does not mach channel type (analog/digital)

Examples

>>> from nistreamer import NIStreamer, std_fn_lib
>>>
>>> strmr = NIStreamer()
>>> ao_card = strmr.add_ao_card(max_name='Dev1', samp_rate=1e6)
>>> ao_0 = ao_card.add_chan(chan_idx=0)
>>>
>>> ao_0.add_gothis_instr(
>>>     func=std_fn_lib.Sine(amp=1.0, freq=2e3),
>>>     t=1.0,
>>> )
>>> strmr.compile(stop_time=10.0)

last_instr_end_time()[source]#

Returns the last instruction end time or None if the edit cache is empty.

Return type:: Optional[float]

clear_edit_cache()[source]#: Discards all instructions from this channel.

abstractmethod calc_signal(start_time=None, end_time=None, nsamps=1000)[source]#

Computes channel values for an array of time points.

This function is exposed for channel signal plotting. The nsamps time points are distributed uniformly over the closed interval [start_time, end_time].

Parameters:

start_time (Optional[float]) – interval start. If None, zero time is used
end_time (Optional[float]) – interval end. If None, sequence end is used
nsamps (Optional[int]) – number of points

Returns:

List of corresponding channel values

Raises:

ValueError – if any parameters are invalid, if sequence is not fresh-compiled.

Notes

You may need to select a sufficiently large nsamps and a sufficiently narrow time window to see the true waveform shape that the actual stream would produce when sampling at the hardware clock rate. Otherwise, very narrow pulses may be missed and periodic waveforms may appear distorted due to undersampling.

abstractmethod eval_point(t)[source]#

Computes channel value at time point t.

Unlike calc_signal(), this method does not require sequence compilation. So it can be used in sequence scripting, for instance to “measure” start values for ramps.

CAUTION! The returned value is computed according to the current edit cache, and does not update with any future sequence edits. If later in the script, an instruction is added at earlier time changing the actual value at point t, there may be a discontinuity since the ramp will use the outdated start value that was given to it.

class nistreamer.channel.AOChanProxy(_streamer, _card_max_name, chan_idx, nickname=None)[source]#

Bases: BaseChanProxy

Analog output channel proxy.

property chan_name: str#: Physical channel name.

property dflt_val: float#: The default value for intervals that are not covered by instructions.

property rst_val: float#: The value set by add_reset_instr() command.

calc_signal(start_time=None, end_time=None, nsamps=1000)[source]#

Computes channel values for an array of time points.

This function is exposed for channel signal plotting. The nsamps time points are distributed uniformly over the closed interval [start_time, end_time].

Parameters:

start_time – interval start. If None, zero time is used
end_time – interval end. If None, sequence end is used
nsamps – number of points

Returns:

List of corresponding channel values

Raises:

ValueError – if any parameters are invalid, if sequence is not fresh-compiled.

Notes

eval_point(t)[source]#

Computes channel value at time point t.

Unlike calc_signal(), this method does not require sequence compilation. So it can be used in sequence scripting, for instance to “measure” start values for ramps.

Return type:: float

const(t, dur, val)[source]#

Constant-value pulse with a fixed duration.

Parameters:

t (float) – start time
dur (float) – pulse duration
val (float) – value

Return type:

float

Returns:

Pulse duration

Raises:

ValueError – if this instruction collides with an existing one

Notes

This method does not have the “keep value” option - the channel will transition to the default value at the end of this pulse. Use go_const() if you want to set and keep the constant value instead.

go_const(t, val)[source]#

Set a constant value val at time t and keep it until further instructions.

During compilation, this instruction will automatically fill the full interval until the next instruction start or global sequence end.

sine(t, dur, amp, freq, phase=0, offs=0, keep_val=False)[source]#

Sinusoidal pulse with a fixed duration.

The waveform is parametrized as follows: Sine(t) = amp * sin(2Pi * freq * t + phase) + offs

Parameters:

t (float) – start time
dur (float) – pulse duration
amp (float) – amplitude (Volts)
freq (float) – linear frequency (Hz, 1/period)
phase (Optional[float]) – absolute phase (radians)
offs (Optional[float]) – constant offset (Volts)
keep_val (Optional[bool]) – if True, the last value will be kept after the pulse, otherwise channel goes to default value.

Return type:

float

Returns:

Pulse duration dur

Raises:

ValueError – if this instruction collides with an existing one

go_sine(t, amp, freq, phase=0, offs=0)[source]#

Sinusoidal pulse without a specified duration.

During compilation, this instruction will automatically fill the full interval until the next instruction start or global sequence end.

The waveform is parametrized as follows: Sine(t) = amp * sin(2Pi * freq * t + phase) + offs,

Parameters:

t (float) – start time
amp (float) – amplitude (Volts)
freq (float) – linear frequency (Hz, 1/period)
phase (Optional[float]) – absolute phase (radians)
offs (Optional[float]) – constant offset (Volts)

Raises:

ValueError – if this instruction collides with an existing one

linramp(t, dur, start_val, end_val, keep_val=True)[source]#

Linear ramp.

Connects the points (t, start_val) and (t + dur, end_val) with a linear function. If keep_val=True, the end value will be kept after the pulse, otherwise channel goes to default value.

Return type:: float
Returns:: Duration dur
Raises:: ValueError – if this instruction collides with an existing one

sineramp(t, dur, start_val, end_val, keep_val=True)[source]#

Sinusoidal ramp.

Connects the points (t, start_val) and (t + dur, end_val) with a half-period of a sine function such that the derivative is zero on both ends. If keep_val=True, the end value will be kept after the pulse, otherwise channel goes to default value.

Return type:: float
Returns:: Duration dur
Raises:: ValueError – if this instruction collides with an existing one

class nistreamer.channel.DOChanProxy(_streamer, _card_max_name, port_idx, line_idx, nickname=None)[source]#

Bases: BaseChanProxy

Digital output channel proxy (an individual digital line).

property chan_name: str#: Physical channel name.

property dflt_val: bool#: The default value for intervals that are not covered by instructions.

property rst_val: bool#: The value set by add_reset_instr() command.

property const_fns_only: bool#

Shows if the host card has the “constant functions only” mode enabled.

If enabled, all lines on this card will only accept the following four constant-valued instructions: high(), low(), go_high(), and go_low(). This restriction allows to accelerate the runtime sample computation and significantly reduce the risk of buffer underflow.

In most cases, only constant-valued instructions are used anyway, so this mode is enabled by default. If you need to add non-constant boolean waveforms, set const_fns_only() of the host card to False.

calc_signal(start_time=None, end_time=None, nsamps=1000)[source]#

Computes channel values for an array of time points.

This function is exposed for channel signal plotting. The nsamps time points are distributed uniformly over the closed interval [start_time, end_time].

Parameters:

start_time – interval start. If None, zero time is used
end_time – interval end. If None, sequence end is used
nsamps – number of points

Returns:

List of corresponding channel values

Raises:

ValueError – if any parameters are invalid, if sequence is not fresh-compiled.

Notes

eval_point(t)[source]#

Computes channel value at time point t.

Unlike calc_signal(), this method does not require sequence compilation. So it can be used in sequence scripting, for instance to “measure” start values for ramps.

Return type:: bool

go_high(t)[source]#: Sets the logical high at time t and keeps it until the next instruction start / sequence end.

go_low(t)[source]#: Sets the logical low at time t and keeps it until the next instruction start / sequence end.

high(t, dur)[source]#

Logical-high pulse from time t to t + dur.

Return type:: float
Returns:: Pulse duration dur
Raises:: ValueError – if this instruction collides with an existing one

Notes

This method does not have the “keep value” option - the channel will transition to the default value at the end of this pulse. Use go_high() instruction if you want to set and keep the constant value instead.

low(t, dur)[source]#

Logical-low pulse from time t to t + dur.

Return type:: float
Returns:: Pulse duration dur
Raises:: ValueError – if this instruction collides with an existing one

Notes

This method does not have the “keep value” option - the channel will transition to the default value at the end of this pulse. Use go_low() instruction if you want to set and keep the constant value instead.