Debugging

Misconfigured or uninitialized Arduino pins generate unstable voltage levels that vary with frequency and signal state. During board reset, all pins enter a floating state, producing undefined signals that can affect connected devices. This can lead to data corruption or unpredictable behavior in chips such as EEPROMs or DACs.

The EEPROM Programmer initially returned corrupted data. I tested wiring, bit ordering, and bus isolation, suspecting noise on the data lines. Oscilloscope traces suggested interference, but the root cause was software, several Arduino address pins were never initialized. These floating pins produced unstable signals that mimicked noise. After proper initialization, the API produced stable results identical to a reference programmer.