Firmware

Tuesday, September 22, 2026
in Testing, Firmware, Simulation
3 min read

Fuzzing the Firmware Path in an RP2350 Emulator

The StackCalc calculator board is not assembled yet, but the firmware path is already rich enough to break in interesting ways. A random input sequence can cross number entry, ENTER, stack lift, shifts, menus, modes, clear, correction, and display updates in combinations that a hand-written demo never reaches.

We use the RP2350 emulator to run the firmware image and fuzz those combinations through its keypad contract. That is firmware-emulation evidence, not evidence of a physical switch matrix or display.

Tuesday, September 22, 2026
in Firmware, iOS, RPN
3 min read

One Calculator Core for Watch, Phone, and RP2350

A calculator can look consistent across devices while disagreeing at exactly the moments that teach people how RPN works: ENTER, stack lift, an error state, a program step, or an unfinished number. We did not want the Watch, iPhone, and eventual handheld to agree only on the happy path. StackCalc has one calculator core so a named key sequence has one meaning before any surface decides how to draw it.

The iPhone app exposes the same RPN stack that the firmware-facing path renders into a compact display.

Tuesday, September 22, 2026
in Firmware, Performance, Simulation
3 min read

Profiling the Emulated Firmware Loop Before Board Bring-Up

Power management begins as a behavior problem before it becomes a battery-life number. The StackCalc firmware has to decide when to scan the matrix, wake the display path, skip an unchanged frame, save state, and return to a lower-work loop. We can exercise those decisions in the RP2350 emulator while the PCB is in fabrication.