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Arduino DISCUSSION
The UNO name and familiar APIs can make moving a sketch appear straightforward, but R3 and R4 use different MCU architectures. Which assumptions should be checked when a sketch compiles yet behaves differently?
The example project reads an analog sensor, generates PWM and uses a third-party library.
Reference: Arduino: UNO R4 Minima hardware (https://docs.arduino.cc/hardware/uno-r4-minima/).
Check the library's supported architectures and look for direct register access, assembly, timer assumptions and fixed CPU-frequency calculations. Source that uses only common APIs is easier to move, but its timing can still differ. Pin compatibility and a successful build do not establish equivalent peripheral behavior.
Make ADC resolution, reference selection and PWM requirements explicit. Measure the actual PWM frequency and duty cycle rather than assuming an API value implies the same waveform on every core. Also inspect integer sizes, structure layouts and any binary protocol that sends memory directly.
Bring up the migrated project one peripheral at a time and compare numerical results against a known input. Keep board-core and library versions in the project notes. If exact timing matters, use the target's supported timing facilities and verify them on hardware instead of compensating with arbitrary delays.
