arduino-esp32 3.x ledcWrite takes a PIN and looks up the attached channel
internally. arduino-esp32 2.x (the toolchain version we pin) takes a
CHANNEL. The velxio_compat.h shim already aliased the 3.x-only
ledcAttach onto ledcSetup+ledcAttachPin so 3.x sketches would compile,
but ledcWrite still mapped 1:1 — so a call like
#define R_PIN 16
ledcAttach(R_PIN, 5000, 8); // shim → channel 0 attached to pin 16
ledcWrite(R_PIN, 128); // ★ writes to "channel 16" (invalid)
silently wrote to LEDC channel 16, which doesn't exist (valid range
0-15). The hardware duty register never changed, qemu-lcgamboa never
emitted a `ledc_duty` event, and the RGB LED stayed dark even though
the firmware ran cleanly and the wires looked right. Verified end-to-end
with examples/esp32-pwm-led-rgb: gpio_change events fired at boot, no
ledc_duty events fired, ledRed/ledGreen/ledBlue all stayed at 0.
Fix: maintain a 40-entry pin→channel table populated by both ledcAttach
variants. Replace ledcWrite with a macro that calls a helper checking
the table first; if the value isn't a known pin we pass it through as a
channel, preserving 2.x channel-style call sites.
Macro/function name collision is sidestepped with the standard
parenthesizing trick — `(ledcWrite)(channel, duty)` doesn't expand the
function-like macro because the token isn't followed by `(`.
Verified live on velxio.dev/example/esp32-pwm-led-rgb after hot-copying
the new header into the velxio-app container: ledRed/ledGreen/ledBlue
now cycle through the full HSV wheel as expected (samples: (255,41,0),
(41,255,0), (0,41,255), (232,255,0), …).
Single-file sketch only — the table is `static` (internal linkage) and
ledcAttach + ledcWrite live in the header. Multi-file sketches that
attach in file A and write in file B would each see their own table.
Acceptable for now since arduino-esp32 sketches are nearly always
single-file; revisit when we bump the toolchain to 3.x and can drop the
shim entirely.
A user reported the LEDC PWM RGB example failing to compile. The sketch
calls ledcAttach(pin, freq, resolution) — the one-shot API added in
arduino-esp32 3.x. Our toolchain image pins arduino-esp32 to 2.0.17
(matched to ESP-IDF 4.4.7 + the lcgamboa QEMU ROM), where the API is
the older two-step ledcSetup + ledcAttachPin pair. Sketches written
against 3.x docs hit "ledcAttach was not declared in this scope".
Bumping arduino-esp32 to 3.x means moving to ESP-IDF 5.x, which may
break our QEMU fork. Cheaper fix: ship a compat shim header in the
ESP-IDF project template that defines ledcAttach + ledcAttachChannel
in terms of the 2.x API, gated on `!defined(ledcAttach)` so it
disappears the day we bump.
espidf_compiler.py now injects #include "velxio_compat.h" right after
Arduino.h whether the user explicitly included Arduino.h or we
prepended it ourselves.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
David Montero