A hardware-debugging technique that uses your portable firmware codebase as the diagnostic tool. Plus the deeper bug it exposed once I got past the hardware wall.
I spent a week chasing an I2C bus that refused to ACK. By the end of it, I had soldered the breakout, replaced every jumper, swapped chips, and verified every pin assignment three times. The firmware still reported 0 devices found on every scan.
What finally cracked it wasn't another tweak in the same setup. It was moving the peripheral to a different MCU — and discovering that the same chip, with the same wires, came up 6/6 immediately on a NUCLEO.
Here's the technique, and the bonus firmware bug it exposed once I got past the hardware wall.
The symptom
