SN74HC125N shared-node handoff

Open hc125_handoff/hc125_handoff.ino in the Arduino IDE. Select Arduino
Uno in Arduino AVR Boards 1.8.6. The reader article has the complete
wiring and measurement procedure. Power the UNO over USB and use its
5 V rail for both sides of the fixture. Use a separate measured 2.2 kΩ
resistor in each output branch. All scope ground clips go to common
0 V. Keep BUS on high-impedance instruments only.

Serial monitor: 115200 bits per second. Send g for the guarded gap or
o for the deliberately overlapping case. Both series resistors must
remain installed. Rearm the scope between commands. Record each
control's own midpoint crossing and the shared-node voltage in the
blank worksheet.

Run the delivered mock host tests with Python 3 and a C++17 compiler.

  python3 test_actual_program.py -v

The mock invokes the exact .ino with timestamped GPIO and serial events.
It checks reset preload, ordering, requested wait times, ignored input
and repeat cleanup. Actual pin delays, waveforms and switching margins
require bench observations. This archive contains no firmware binary
or physical observations.
