feat(kernel): add debounced (glitch-filtered) sense-line reads #5

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chris commented 2026-06-20 15:51:36 +02:00

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The IEC bit loop sampled GPIO with a single register read, so a glitch
on a level-shifted 5V<->3.3V bus could corrupt a bit with no chance to
retry (the loop runs with IRQs off). Add a stable-read filter that only
believes a level change after it holds IEC_DEBOUNCE_US (now 5 us); the
fast path is a single read so tight CLK polls stay cheap. Used across
the receive hot path; the ATN ISR and self-test keep raw reads.

Generated by Clanker

The IEC bit loop sampled GPIO with a single register read, so a glitch on a level-shifted 5V<->3.3V bus could corrupt a bit with no chance to retry (the loop runs with IRQs off). Add a stable-read filter that only believes a level change after it holds IEC_DEBOUNCE_US (now 5 us); the fast path is a single read so tight CLK polls stay cheap. Used across the receive hot path; the ATN ISR and self-test keep raw reads. Generated by Clanker

chris added 1 commit 2026-06-20 15:51:36 +02:00

feat(kernel): add debounced (glitch-filtered) sense-line reads ... acfce76011

The IEC bit loop sampled GPIO with a single register read, so a glitch
on a level-shifted 5V<->3.3V bus could corrupt a bit with no chance to
retry (the loop runs with IRQs off). Add a stable-read filter that only
believes a level change after it holds IEC_DEBOUNCE_US (now 5 us); the
fast path is a single read so tight CLK polls stay cheap. Used across
the receive hot path; the ATN ISR and self-test keep raw reads.

Generated by Clanker

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

chris added 1 commit 2026-06-20 16:09:45 +02:00

refactor(kernel): align GPIO pin layout with the reference listener ... b2e4f9710d

Adopt the confirmed-working reference's pin assignment so the module runs
on that proven wiring: DATA=BCM2 (pin 3), CLK=BCM3 (pin 5), ATN=BCM4
(pin 7). RESET is kept and relocated to BCM17 (pin 11), the pin freed by
moving CLK. All five GPIOs stay in bank 0, so the direct-register hot
path and ATN IRQ are unchanged -- only the IEC_GPIO_* defines, the
device-tree overlay, and the docs/self-test move.

DATA/CLK now sit on the ARM I2C pins (GPIO2/3) with the SoC's fixed
~1.8k pull-ups; keep dtparam=i2c_arm off. The bare-board self-test
expectation changes from 0x15 to 0x0b accordingly.

Generated by Clanker

chris added 1 commit 2026-06-20 17:25:48 +02:00

yes 63adefea86

chris added 1 commit 2026-06-20 18:01:24 +02:00

adjust debounce time 3cf13f14f2

chris added 5 commits 2026-06-20 18:21:10 +02:00

feat(iecpoc): add plain-text output mode with --debug flag ... d359aa4acc

Default output now shows only the received characters; CR/LF become real
newlines and LISTEN/UNLISTEN print a clearly visible divider. Pass --debug
to restore the previous full annotated trace.

Generated by Clanker

test(iecpoc): add plain-mode tests for TraceFormatter ... 0d6034702a

Covers the plain property, per-record-type output (printable chars,
CR/LF newlines, LISTEN/UNLISTEN dividers, silenced events and other
commands), and a full-session integration check.

Generated by Clanker

docs(launch): update usage comments for plain-text default ... affdcdda6b

The default output is now plain text, not an annotated trace. Updated the
header comment and added a --debug example.

Generated by Clanker

docs(kernel): document frontend output modes ... 565b58480a

Added a 'Frontend output modes' section explaining plain text (default),
--debug (annotated trace), and --raw (hex), with launch.sh examples for
each.

Generated by Clanker

update workflow 63c3167d9f

chris added 3 commits 2026-06-20 18:48:27 +02:00

data was bricked reverting debounce to 5 dba7b5c43c

update workflow to package the scripts with execute permission hopefully 8bb6058a04

maybe fix program not exiting 6c549b164c

chris added 2 commits 2026-06-22 00:10:07 +02:00

fix(iec_listener): serialize DATA line control to fix missed command bytes ... ec615dbb80

The worker kthread and ATN ISR both modify the DATA line by changing GPIO2's
direction (open-drain emulation). On quad-core Pi they run simultaneously on
different CPUs, causing their read-modify-write operations on the shared GPFSEL0
register to clobber each other. The ISR's ATN presence-acknowledge could be
erased by the worker's ready-for-data release, causing the C64 to see "device
not present" and drop LISTEN/UNLISTEN command bytes.

Add iec_data_lock spinlock and two synchronized wrappers:
- iec_data_assert_sync(): serializes DATA assert
- iec_data_release_sync(): serializes DATA release and refuses to release while
  ATN is asserted, preventing the acknowledge from being undone

Convert all worker and ISR DATA accesses to use the _sync() wrappers. Keep raw
unconditional helpers for init/exit/self-test (exit must free the bus
unconditionally; self-test probes directly).

Generated by Clanker 🤖

docs(kernel): document DATA line locking design to prevent RMW collisions ... 2015d4c96e

Add row to "Decisions baked into the code" table explaining the DATA line
control design: all DATA assert/release operations in the worker and ATN ISR
go through iec_data_*_sync() under iec_data_lock to serialize the GPFSEL0
read-modify-write across CPUs. The release wrapper refuses to release while
ATN is asserted, preventing the ready-for-data release from erasing the ISR's
presence acknowledge — the bug that caused intermittently missed
LISTEN/UNLISTEN commands. Init/exit/self-test keep raw unconditional helpers.

Generated by Clanker 🤖

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Reference: chris/comodore-iec-emu#5

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