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zhindesZach Hindes
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Zach Hindes
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add an nidaqmx example with an fft (#210)
* add an nidaqmx example with an fft * oops * black * code review * lint * back to cast * cleanup * words --------- Co-authored-by: Zach Hindes <zach.hindes@emerson.com>
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‎examples/nidaqmx/nidaqmx_analog_input_fft/README.md‎

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# NI-DAQmx Analog Input with FFT Example
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### Overview
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This is a nipanel example that acquires a continuous amount of data using the DAQ device's internal clock and graphs the acquired data in both the time domain and frequency domain in an interactive Streamlit panel.
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### Features
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- NI-DAQmx Python configuration and acquisition
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- Displays data in an interactive chart using ECharts
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- Updates automatically as new data is acquired
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### Prerequisites
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- Python 3.10 or later
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- InstrumentStudio 2026 Q1 or later
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- A physical or simulated device, refer to the [NI-DAQmx Python README (Getting Started section)](https://github.com/ni/nidaqmx-python/blob/master/README.rst#getting-started)
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### Usage
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```pwsh
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poetry install --with examples
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poetry run python examples\nidaqmx\nidaqmx_analog_input_fft\nidaqmx_analog_input_fft.py
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```

‎examples/nidaqmx/nidaqmx_analog_input_fft/nidaqmx_analog_input_fft.py‎

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"""Example of analog input voltage acquisition with a Fast Fourier Transform.
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This example demonstrates how to acquire a continuous amount of data using the
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DAQ device's internal clock. The settings are configured from the Streamlit
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panel, and the acquired data is displayed on a graph. An FFT is computed from
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the acquired data and displayed on a separate graph. Refer to the panel script
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for details: nidaqmx_analog_input_fft_panel.py
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"""
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import time
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from pathlib import Path
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from typing import cast
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import nidaqmx
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import nidaqmx.system
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import numpy as np
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from nidaqmx.constants import (
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AcquisitionType,
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TerminalConfiguration,
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UsageTypeAI,
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)
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from nidaqmx.errors import DaqError
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from nitypes.waveform import AnalogWaveform
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import nipanel
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panel_script_path = Path(__file__).with_name("nidaqmx_analog_input_fft_panel.py")
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panel = nipanel.create_streamlit_panel(panel_script_path)
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panel.set_value("is_running", False)
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system = nidaqmx.system.System.local()
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available_voltage_channels = []
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for dev in system.devices:
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for chan in dev.ai_physical_chans:
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if UsageTypeAI.VOLTAGE in chan.ai_meas_types:
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available_voltage_channels.append(chan.name)
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panel.set_value("available_voltage_channels", available_voltage_channels)
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print(f"Panel URL: {panel.panel_url}")
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print(f"Waiting for the 'Run' button to be pressed...")
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print(f"(Press Ctrl + C to quit)")
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try:
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while True:
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while not panel.get_value("is_running", False):
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time.sleep(0.1)
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print(f"Running...")
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try:
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# How to use nidaqmx: https://nidaqmx-python.readthedocs.io/en/stable/
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panel.set_value("daq_error", "")
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with nidaqmx.Task() as task:
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task.ai_channels.add_ai_voltage_chan(
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physical_channel=panel.get_value("voltage_channel", ""),
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min_val=panel.get_value("voltage_min_value", -5.0),
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max_val=panel.get_value("voltage_max_value", 5.0),
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terminal_config=panel.get_value(
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"terminal_configuration", TerminalConfiguration.DEFAULT
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),
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)
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task.timing.cfg_samp_clk_timing(
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rate=panel.get_value("sample_rate_input", 1000.0),
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sample_mode=AcquisitionType.CONTINUOUS,
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samps_per_chan=panel.get_value("samples_per_channel", 100),
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)
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panel.set_value("sample_rate", task.timing.samp_clk_rate)
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try:
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print(f"Starting data acquisition...")
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samples_per_channel = panel.get_value("samples_per_channel", 100)
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task.start()
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while panel.get_value("is_running", False):
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waveform = cast(
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AnalogWaveform[np.float64],
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task.read_waveform(number_of_samples_per_channel=samples_per_channel),
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)
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panel.set_value("voltage_waveform", waveform)
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# calculate the Discrete Fourier Transform
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fft = np.fft.fft(waveform.scaled_data)
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dft_sample_freqs = np.fft.fftfreq(
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waveform.sample_count, d=waveform.timing.sample_interval.total_seconds()
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)
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# convert to decibels
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magnitudes = np.abs(fft)
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normalized_magnitudes = magnitudes / np.max(magnitudes)
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dbs = 20 * np.log10(normalized_magnitudes)
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# only graph up to Nyquist
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num_freqs_to_graph = samples_per_channel // 2
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panel.set_value("fft_freqs", dft_sample_freqs[0:num_freqs_to_graph])
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panel.set_value("fft_mags", dbs[0:num_freqs_to_graph])
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except KeyboardInterrupt:
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raise
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finally:
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print(f"Stopping data acquisition...")
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task.stop()
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panel.set_value("is_running", False)
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print(f"Stopped")
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except DaqError as e:
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daq_error = str(e)
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panel.set_value("daq_error", daq_error)
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panel.set_value("is_running", False)
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print(f"ERRORED")
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except KeyboardInterrupt:
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pass

‎examples/nidaqmx/nidaqmx_analog_input_fft/nidaqmx_analog_input_fft_panel.py‎

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"""Streamlit visualization script to display data acquired by nidaqmx_continuous_analog_input.py."""
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from typing import cast
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import hightime as ht
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import streamlit as st
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from nidaqmx.constants import (
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TerminalConfiguration,
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)
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from nitypes.waveform import AnalogWaveform
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from streamlit_echarts import st_echarts
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import nipanel
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from nipanel.controls import enum_selectbox
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st.set_page_config(
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page_title="NI-DAQmx - Analog Input - Voltage with FFT", page_icon="📈", layout="wide"
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)
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st.markdown(
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"""
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<style>
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div[data-baseweb="select"] {
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max-width: 250px !important;
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}
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div.stNumberInput {
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max-width: 250px !important;
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}
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div.stTextInput {
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max-width: 250px !important;
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}
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</style>
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""",
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unsafe_allow_html=True,
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)
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def _click_start() -> None:
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panel.set_value("is_running", True)
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def _click_stop() -> None:
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panel.set_value("is_running", False)
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panel = nipanel.get_streamlit_panel_accessor()
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st.header("NI-DAQmx - Analog Input - Voltage with FFT")
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if panel.get_value("is_running", False):
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st.button(r"⏹️ Stop", key="stop_button", on_click=_click_stop)
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else:
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st.button(r"▶️ Run", key="run_button", on_click=_click_start)
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sample_rate = panel.get_value("sample_rate", 0.0)
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# Create two-column layout for the entire interface
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left_column, right_column = st.columns([1, 1])
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# Left column - Channel tabs and Timing Settings
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with left_column:
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# Channel Settings tabs
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with st.container(border=True):
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st.header("Channel Settings")
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voltage_tab = st.tabs(["Voltage"])[0]
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voltage_tab.header("Voltage")
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with voltage_tab:
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channel_left_column, channel_right_column = st.columns(2)
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with channel_left_column:
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st.selectbox(
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options=panel.get_value("available_voltage_channels", [""]),
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index=0,
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label="Voltage Channel",
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disabled=panel.get_value("is_running", False),
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key="voltage_channel",
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)
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st.number_input(
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"Min Value",
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value=-5.0,
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step=0.1,
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disabled=panel.get_value("is_running", False),
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key="voltage_min_value",
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)
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st.number_input(
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"Max Value",
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value=5.0,
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step=0.1,
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disabled=panel.get_value("is_running", False),
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key="voltage_max_value",
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)
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with channel_right_column:
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enum_selectbox(
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panel,
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label="Terminal Configuration",
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value=TerminalConfiguration.DEFAULT,
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disabled=panel.get_value("is_running", False),
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key="terminal_configuration",
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)
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# Timing Settings section in left column
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with st.container(border=True):
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st.header("Timing Settings")
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timing_left_column, timing_right_column = st.columns(2)
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with timing_left_column:
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st.selectbox(
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options=["OnboardClock"],
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label="Sample Clock Source",
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disabled=True,
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)
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st.number_input(
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"Sample Rate",
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value=1000.0,
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step=100.0,
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min_value=1.0,
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disabled=panel.get_value("is_running", False),
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key="sample_rate_input",
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)
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with timing_right_column:
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st.number_input(
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"Samples to Read",
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value=1000,
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step=100,
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min_value=10,
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disabled=panel.get_value("is_running", False),
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key="samples_per_channel",
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)
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st.text_input(
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label="Actual Sample Rate",
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value=str(sample_rate) if sample_rate else "",
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disabled=True,
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)
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# Right column - Graph
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with right_column:
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if panel.get_value("daq_error", "") != "":
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st.error(
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f"There was an error running the script. Fix the issue and click Run again. \n\n {panel.get_value('daq_error', '')}"
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)
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else:
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with st.container(border=True):
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# Voltage Data Graph section
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st.header("Acquired Data")
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voltage_waveform = panel.get_value("voltage_waveform", AnalogWaveform())
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if voltage_waveform.sample_count == 0:
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time_labels = ["00:00:00.000"]
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else:
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timestamps = cast(
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list[ht.datetime],
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list(voltage_waveform.timing.get_timestamps(0, voltage_waveform.sample_count)),
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)
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time_labels = [
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f"{ts.hour:02d}:{ts.minute:02d}:{ts.second:02d}.{ts.microsecond//1000:03d}"
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for ts in timestamps
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]
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voltage_graph = {
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"animation": False,
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"tooltip": {"trigger": "axis"},
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"legend": {"data": [voltage_waveform.units]},
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"xAxis": {
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"type": "category",
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"data": time_labels,
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"name": "Time",
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"nameLocation": "center",
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"nameGap": 40,
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},
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"yAxis": {
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"type": "value",
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"name": "Measurement",
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"nameRotate": 90,
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"nameLocation": "center",
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"nameGap": 40,
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},
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"series": [
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{
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"name": voltage_waveform.units,
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"type": "line",
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"data": list(voltage_waveform.scaled_data),
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"emphasis": {"focus": "series"},
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"smooth": True,
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"seriesLayoutBy": "row",
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},
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],
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}
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st_echarts(options=voltage_graph, height="300px", key="voltage_graph")
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frequencies = panel.get_value("fft_freqs", [0.0])
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magnitudes = panel.get_value("fft_mags", [0.0])
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fft_data = [{"value": [x, y]} for x, y in zip(frequencies, magnitudes)]
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fft_graph = {
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"animation": False,
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"tooltip": {"trigger": "axis"},
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"legend": {"data": ["Magnitude"]},
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"xAxis": {
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"type": "value",
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"name": "Frequency",
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"nameLocation": "center",
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"nameGap": 40,
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},
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"yAxis": {
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"type": "value",
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"name": "Magnitude",
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"nameRotate": 90,
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"nameLocation": "center",
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"nameGap": 40,
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},
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"series": [
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{
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"name": "Magnitude",
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"type": "line",
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"data": fft_data,
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"emphasis": {"focus": "series"},
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"smooth": True,
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"seriesLayoutBy": "row",
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},
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],
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}
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st_echarts(options=fft_graph, height="300px", key="fft_graph")

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