How to Build a Test Panel GUI with TofuPilot

Building a custom operator panel lets your test technicians run tests without touching the command line. This guide shows how to create a tkinter-based GUI that controls instruments, collects serial numbers, and runs OpenHTF tests with TofuPilot logging.

Prerequisites

Python 3.8+
OpenHTF installed (pip install openhtf)
TofuPilot Python SDK installed (pip install tofupilot)
A TofuPilot API key configured

Step 1: Create the Main Panel Layout

Start with a basic tkinter window that has a serial number entry, instrument controls, and a test execution area.

panel.py

import tkinter as tkfrom tkinter import ttkimport threadingclass TestPanel:    def __init__(self, root):        self.root = root        self.root.title("Test Panel")        self.root.geometry("480x520")        self.root.resizable(False, False)        self.instrument_connected = False        self._build_instrument_frame()        self._build_serial_frame()        self._build_control_frame()        self._build_status_frame()    def _build_instrument_frame(self):        frame = ttk.LabelFrame(self.root, text="Instrument", padding=10)        frame.pack(fill="x", padx=10, pady=(10, 5))        self.connect_btn = ttk.Button(            frame, text="Connect", command=self._connect_instrument        )        self.connect_btn.pack(side="left", padx=(0, 5))        self.disconnect_btn = ttk.Button(            frame, text="Disconnect", command=self._disconnect_instrument, state="disabled"        )        self.disconnect_btn.pack(side="left")        self.instr_status = ttk.Label(frame, text="Disconnected", foreground="gray")        self.instr_status.pack(side="right")    def _build_serial_frame(self):        frame = ttk.LabelFrame(self.root, text="Unit Under Test", padding=10)        frame.pack(fill="x", padx=10, pady=5)        ttk.Label(frame, text="Serial Number:").pack(anchor="w")        self.serial_var = tk.StringVar()        self.serial_entry = ttk.Entry(frame, textvariable=self.serial_var, width=30)        self.serial_entry.pack(fill="x", pady=(2, 0))    def _build_control_frame(self):        frame = ttk.Frame(self.root, padding=10)        frame.pack(fill="x", padx=10)        self.start_btn = ttk.Button(            frame, text="Start Test", command=self._start_test, state="disabled"        )        self.start_btn.pack(fill="x")    def _build_status_frame(self):        frame = ttk.LabelFrame(self.root, text="Status", padding=10)        frame.pack(fill="both", expand=True, padx=10, pady=(5, 10))        self.result_label = ttk.Label(            frame, text="Idle", font=("Helvetica", 18, "bold"), anchor="center"        )        self.result_label.pack(pady=(0, 10))        self.log_text = tk.Text(frame, height=10, state="disabled", font=("Courier", 10))        self.log_text.pack(fill="both", expand=True)    def _log(self, message):        self.log_text.configure(state="normal")        self.log_text.insert("end", message + "")        self.log_text.see("end")        self.log_text.configure(state="disabled")    def _set_result(self, text, color):        self.result_label.configure(text=text, foreground=color)    def _connect_instrument(self):        self._log("Connecting to instrument...")        self.instrument_connected = True        self.instr_status.configure(text="Connected", foreground="green")        self.connect_btn.configure(state="disabled")        self.disconnect_btn.configure(state="normal")        self.start_btn.configure(state="normal")        self._log("Instrument connected.")    def _disconnect_instrument(self):        self._log("Disconnecting instrument...")        self.instrument_connected = False        self.instr_status.configure(text="Disconnected", foreground="gray")        self.connect_btn.configure(state="normal")        self.disconnect_btn.configure(state="disabled")        self.start_btn.configure(state="disabled")        self._log("Instrument disconnected.")    def _start_test(self):        serial = self.serial_var.get().strip()        if not serial:            self._log("Error: enter a serial number.")            return        self.start_btn.configure(state="disabled")        self.serial_entry.configure(state="disabled")        self._set_result("Running...", "orange")        self._log(f"Starting test for {serial}...")        thread = threading.Thread(target=self._run_test, args=(serial,), daemon=True)        thread.start()    def _run_test(self, serial):        # Placeholder — see Step 4 for full implementation        passif __name__ == "__main__":    root = tk.Tk()    app = TestPanel(root)    root.mainloop()

This gives you a clean panel with instrument connect/disconnect buttons, a serial number field, and a status area that shows logs and pass/fail results.

Step 2: Add an Instrument Plug

Create an OpenHTF plug that wraps your instrument communication. This example simulates a power supply, but you'd replace the internals with your actual SCPI or serial commands.

instrument_plug.py

import timeimport openhtf as htfclass PowerSupplyPlug(htf.plugs.BasePlug):    """Plug for controlling a bench power supply."""    ADDRESS = "GPIB0::5::INSTR"    def setUp(self):        self._connected = False        self._voltage = 0.0        # Replace with real instrument connection (e.g., pyvisa)        self._connected = True    def set_voltage(self, voltage):        if not self._connected:            raise RuntimeError("Power supply not connected")        self._voltage = voltage        time.sleep(0.3)    def measure_current(self):        if not self._connected:            raise RuntimeError("Power supply not connected")        time.sleep(0.2)        return 0.125    def tearDown(self):        if self._connected:            self.set_voltage(0.0)            self._connected = False

The tearDown method runs automatically when the test finishes, so the instrument always returns to a safe state.

Step 3: Define OpenHTF Test Phases

Write test phases that use the instrument plug to take measurements. Note how plug injection uses the @htf.plug decorator.

test_phases.py

import openhtf as htffrom openhtf.util import unitsfrom instrument_plug import PowerSupplyPlug@htf.plug(psu=PowerSupplyPlug)@htf.measures(    htf.Measurement("supply_voltage_setpoint").with_units(units.VOLT),    htf.Measurement("quiescent_current")        .in_range(minimum=0.05, maximum=0.25)        .with_units(units.AMPERE),)def phase_quiescent_current(test, psu):    """Measure quiescent current at nominal voltage."""    psu.set_voltage(3.3)    test.measurements.supply_voltage_setpoint = 3.3    current = psu.measure_current()    test.measurements.quiescent_current = current@htf.plug(psu=PowerSupplyPlug)@htf.measures(    htf.Measurement("overcurrent_detected").equals(True),)def phase_overcurrent_protection(test, psu):    """Verify the DUT triggers overcurrent protection at high voltage."""    psu.set_voltage(5.5)    test.measurements.overcurrent_detected = True

Each phase focuses on one thing. The measurement validators (.in_range, .equals) tell OpenHTF what counts as a pass or fail.

Step 4: Wire the GUI to OpenHTF Execution

Now connect the panel's _run_test method to actually execute the OpenHTF test with TofuPilot logging.

panel_with_test.py

import tkinter as tkfrom tkinter import ttkimport threadingimport openhtf as htffrom tofupilot.openhtf import TofuPilotfrom test_phases import phase_quiescent_current, phase_overcurrent_protectionclass TestPanel:    def __init__(self, root):        self.root = root        self.root.title("Test Panel")        self.root.geometry("480x520")        self.root.resizable(False, False)        self.instrument_connected = False        self._build_instrument_frame()        self._build_serial_frame()        self._build_control_frame()        self._build_status_frame()    def _build_instrument_frame(self):        frame = ttk.LabelFrame(self.root, text="Instrument", padding=10)        frame.pack(fill="x", padx=10, pady=(10, 5))        self.connect_btn = ttk.Button(            frame, text="Connect", command=self._connect_instrument        )        self.connect_btn.pack(side="left", padx=(0, 5))        self.disconnect_btn = ttk.Button(            frame, text="Disconnect", command=self._disconnect_instrument, state="disabled"        )        self.disconnect_btn.pack(side="left")        self.instr_status = ttk.Label(frame, text="Disconnected", foreground="gray")        self.instr_status.pack(side="right")    def _build_serial_frame(self):        frame = ttk.LabelFrame(self.root, text="Unit Under Test", padding=10)        frame.pack(fill="x", padx=10, pady=5)        ttk.Label(frame, text="Serial Number:").pack(anchor="w")        self.serial_var = tk.StringVar()        self.serial_entry = ttk.Entry(frame, textvariable=self.serial_var, width=30)        self.serial_entry.pack(fill="x", pady=(2, 0))    def _build_control_frame(self):        frame = ttk.Frame(self.root, padding=10)        frame.pack(fill="x", padx=10)        self.start_btn = ttk.Button(            frame, text="Start Test", command=self._start_test, state="disabled"        )        self.start_btn.pack(fill="x")    def _build_status_frame(self):        frame = ttk.LabelFrame(self.root, text="Status", padding=10)        frame.pack(fill="both", expand=True, padx=10, pady=(5, 10))        self.result_label = ttk.Label(            frame, text="Idle", font=("Helvetica", 18, "bold"), anchor="center"        )        self.result_label.pack(pady=(0, 10))        self.log_text = tk.Text(frame, height=10, state="disabled", font=("Courier", 10))        self.log_text.pack(fill="both", expand=True)    def _log(self, message):        self.log_text.configure(state="normal")        self.log_text.insert("end", message + "")        self.log_text.see("end")        self.log_text.configure(state="disabled")    def _set_result(self, text, color):        self.result_label.configure(text=text, foreground=color)    def _connect_instrument(self):        self._log("Connecting to instrument...")        self.instrument_connected = True        self.instr_status.configure(text="Connected", foreground="green")        self.connect_btn.configure(state="disabled")        self.disconnect_btn.configure(state="normal")        self.start_btn.configure(state="normal")        self._log("Instrument connected.")    def _disconnect_instrument(self):        self._log("Disconnecting instrument...")        self.instrument_connected = False        self.instr_status.configure(text="Disconnected", foreground="gray")        self.connect_btn.configure(state="normal")        self.disconnect_btn.configure(state="disabled")        self.start_btn.configure(state="disabled")        self._log("Instrument disconnected.")    def _start_test(self):        serial = self.serial_var.get().strip()        if not serial:            self._log("Error: enter a serial number.")            return        self.start_btn.configure(state="disabled")        self.serial_entry.configure(state="disabled")        self._set_result("Running...", "orange")        self._log(f"Starting test for {serial}...")        thread = threading.Thread(target=self._run_test, args=(serial,), daemon=True)        thread.start()    def _run_test(self, serial):        try:            test = htf.Test(                phase_quiescent_current,                phase_overcurrent_protection,                procedure_id="PCB-FUNC-001",                part_number="PCB-2400",            )            with TofuPilot(test):                test_record = test.execute(test_start=lambda: serial)            outcome = test_record.outcome.name            if outcome == "PASS":                self.root.after(0, self._set_result, "PASS", "green")                self.root.after(0, self._log, f"Test PASSED for {serial}.")            else:                self.root.after(0, self._set_result, "FAIL", "red")                self.root.after(0, self._log, f"Test FAILED for {serial}.")        except Exception as e:            self.root.after(0, self._set_result, "ERROR", "red")            self.root.after(0, self._log, f"Error: {e}")        finally:            self.root.after(0, self._reset_controls)    def _reset_controls(self):        self.serial_entry.configure(state="normal")        self.serial_var.set("")        if self.instrument_connected:            self.start_btn.configure(state="normal")if __name__ == "__main__":    root = tk.Tk()    app = TestPanel(root)    root.mainloop()

A few things to note here:

test.execute runs synchronously in the background thread, so the GUI stays responsive.
root.after(0, ...) schedules GUI updates on the main thread. Tkinter isn't thread-safe, so you can't call widget methods directly from a worker thread.
TofuPilot(test) wraps execution and automatically uploads the test record, including all measurements and outcomes.