The firmware has been printing all along and nothing was listening. USART1 has no
real model here -- it is one of the logging catch-all stubs -- so every byte went
into qemu_log_mask(LOG_UNIMP) and vanished.
Two things were needed, and the second was not in the plan:
1. Print USART1 DR writes (+0x04, per the vendor CMSIS header) as SERIAL lines.
2. Report TXE|TC in USART1 SR. This is the part I had missed. UART_Send() in
App/driver/uart.c spins on LL_USART_IsActiveFlag_TXE() with a bounded timeout
and *skips the byte* when the flag never sets. A stub returning 0 for SR meant
the firmware discarded its own output before it ever reached DR -- the only
write arriving was UART_Init()'s priming zero. So step 1 alone produced
nothing, which is why the first attempt looked like "the build has no logging".
Then a bug of my own: the priming byte is 0x00, I buffered it, and fprintf("%s")
stopped at that NUL and printed an empty line while all 46 bytes sat behind it.
NULs are now dropped, and a line flushes on CR as well as LF.
Verified: SERIAL UV-K5 Firmware, EGZUMER-F4HWN+NR7Y c91cec95
keypad_test.py still passes, which matters because this file is where removing
three fprintfs once silently deleted the keypad.
The previous commit removed three TRACE fprintfs from py32f071.c as
cleanup. That silently broke the keypad completely -- no press reached the
UI, and nothing warned about it.
Root cause is dead-code elimination, not the printing.
qdev_init_gpio_out_named() is inlinable and only records the row_out array;
the lines are filled in later by qdev_connect_gpio_out_named() from board
code, which GCC cannot see. At -O2 GCC therefore proves every element is
still NULL, sees that qemu_set_irq() returns immediately on a NULL irq, and
deletes the body of keypad_update_rows() along with all five calls to it. No
row line is ever driven and the firmware's scan reads all-high.
From the object code:
callers reaching keypad_update_rows
plain none -- the calls are gone
volatile keypad_key_changed, keypad_col_changed, keypad_set_press,
keypad_reset, uvk5_machine_init
keypad_col_changed compiles to a store and a ret with no call at all; with
volatile it ends in jmp keypad_update_rows. Declaring row_out volatile fixes
it at the cause. 10/10 on the press test, 3/3 on keypad_test.py, no build
warnings.
Scoped rather than assumed: PY32GpioState::out is not affected. Marking it
volatile too gives a byte-identical object file, because py32_gpio_write()
is only reachable through a MemoryRegionOps function-pointer table so GCC
cannot enumerate its callers. It stays plain.
Adds tools/keypad_test.py: boots its own instance on private ports and
checks that a short MENU press opens the menu, DOWN moves the cursor, and a
held key is visible to the scan. This is what should have caught the
breakage before it was pushed.
Docs corrected. The breakage had been written up as "power save stops the
keypad scan" and called a gap in the model; it was neither. AGENTS.md now
records the mechanism, the measurements, the objdump check, and the two
measurement traps that made this hard: reading gKeyReading0 after releasing
the key (always KEY_INVALID), and trusting a gdb breakpoint on
KEYBOARD_Poll (with the guest stopped the scan's delays cost no guest time,
so Poll returns KEY_MENU on a build where it fails when running free).
README screenshots regenerated from the current build.
key.py held every key for 2500 ms, on the assumption that guest time runs
fast during delays so a press needs a long wall-clock hold. That is wrong
for this path, and it is why the keypad looked dead.
The two SysTick mechanisms are separate. poll-boost accelerates counter
*reads* so SYSTICK_DelayUs converges; it does not speed up interrupt
delivery. Interrupts drive SysTick_Handler -> gNextTimeslice ->
APP_TimeSlice10ms -> CheckKeys at close to real time, so the firmware's
thresholds hold in wall clock as written: 20 ms to register a press,
400 ms to count as held.
2500 ms is ~250 ticks, six times past the long-press threshold, so every
press was dispatched as a hold. MAIN_Key_MENU acts only on a short release
and returns early when bKeyHeld is set, so nothing happened. Confirmed by
reading gDebounceCounter mid-hold: 317 after a 3 s hold, which also proves
the timeslice was running all along.
Now HOLD_MS=200 and LONG_HOLD_MS=900. Verified with screenshots: the menu
opens and UP/DOWN move through it.
Also here:
- Drop the three TRACE fprintfs. They fired on every keypad poll and
buried the console; the matrix is confirmed working.
- Drop a redundant forward declaration of py32_spi_xfer_byte, silencing
the only build warning.
- Document the real remaining gap: power save (~6 s after boot) stops the
keypad scan and the model does not wake from it. Includes the two dead
ends already ruled out by experiment, so nobody repeats them.
- Add README screenshots captured from guest memory.
Adds a QEMU machine for the Puya PY32F071 (Cortex-M0+) so Quansheng UV-K5 V3
firmware can run on a PC. The firmware boots to its main loop in about five
seconds and the LCD contents are readable.
Register layouts come from the vendor CMSIS header shipped with the firmware
rather than guesswork. Modelled: RCC, GPIO, ADC, both SPI controllers, DMA1 and
the PY25Q16 flash; everything else answers through a logging catch-all, which is
how the next thing worth modelling gets identified.
Seven things had to be right before it would boot, each found by watching where
the firmware stopped: flash aliased at the application offset, clock ready bits,
self-clearing ADC calibration, SPI transfer flags, DMA-driven flash reads,
SysTick poll acceleration, and the bit-banged transceiver bus idling low.
SysTick needs explanation. SYSTICK_DelayUs polls the counter and accumulates
differences; under emulation a register read costs far more relative to guest
time, so a measured 120 ms delay would have taken about 7.7 hours. Lowering the
clock does not help because the bottleneck is loop iterations, not counter speed.
Reporting a value that runs ahead of the real counter does, via a new poll-boost
property on SysTick. Guest time therefore runs fast during delays: fine for
exercising menus and control flow, wrong for judging signal timing.
Also includes the host build of the CW timing chain (harness, stubs, shim,
tests), which compiles app/cwkeyer.c and app/cwmacro.c unmodified against stub
drivers with a virtual clock and scripted paddle input.
Known gap: keypad rows reach the firmware's scan and KEYBOARD_Poll returns the
right key code, but the UI does not react yet.
Not modelled, and not intended to be: radio behaviour. The transceiver chip has
no public datasheet, so keying envelopes and emissions need real hardware.
mckero