fix: analogWrite() silently fails when PWM pin lookup fails on Uno Q#427
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## Problem On Arduino Uno Q, calling analogWrite() on any pin silently returns without doing anything in two cases: 1. When pwm_pin_index() cannot find the pin in the arduino_pwm_pins[] lookup table (idx >= ARRAY_SIZE(arduino_pwm)) 2. When pwm_is_ready_dt() returns false for the PWM device This causes analogWrite() to appear completely broken to users - no output, no error, no warning. The function just silently does nothing. ## Root Cause The pwm-pin-gpios mapping in the Uno Q device tree overlay is missing some pins (D0, D1, D4 are absent or commented out). This means pwm_pin_index() returns (size_t)-1 for those pins, which is always >= ARRAY_SIZE(arduino_pwm), causing an immediate silent return. ## Fix Added a digitalWrite() fallback in both early-return paths: - If PWM lookup fails → fall back to digitalWrite HIGH/LOW - If PWM device not ready → fall back to digitalWrite HIGH/LOW This ensures analogWrite() always produces some output even when hardware PWM is unavailable, which is consistent with how other Arduino cores handle non-PWM pins. ## Testing Tested on Arduino Uno Q with: - Motor driver (SmartElex L298N integrated board) - Confirmed analogWrite() was completely silent before fix - Confirmed digitalWrite() fallback works correctly after fix - Pins tested: 3, 4, 5, 6, 7, 8, 9, 10 ## Impact - No breaking changes - Existing PWM functionality unchanged - Non-PWM pins now behave like standard Arduino (HIGH if value > 127) - Fixes user confusion when analogWrite() silently does nothing
pillo79
approved these changes
Apr 15, 2026
Built
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| Artifact | Board | Core | Tests | RAM | Sketches | Warnings | Errors |
|---|---|---|---|---|---|---|---|
✅ zephyr_contrib |
ek_ra8d1
| 📗 | ✅ |
11.9% |
2 | - | - |
frdm_mcxn947
| 6 🏷️ | ✅ |
58.0% |
2 | - | - | |
frdm_rw612
| 2 🏷️ | ✅ |
83.0% |
2 | - | - | |
✔️* zephyr_main |
giga
| 4 🏷️ | ✅* |
54.6% |
50 | 12 | - |
nano33ble
| 1 🏷️ | ✅* |
78.8% |
28 | 10 | - | |
nano_matter
| 📗 | ✔️* |
|
20 | 8 | (2*) | |
nicla_vision
| 4 🏷️ | ✔️* |
56.9% |
50 | 12 | (10*) | |
niclasense
| 2 🏷️ | ✅* |
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26 | 10 | - | |
opta
| 4 🏷️ | ✅* |
56.5% |
60 | 26 | - | |
portentac33
| 3 🏷️ | ✔️* |
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56 | 26 | (8*) | |
portentah7
| 3 🏷️ | ✅* |
57.1% |
64 | 26 | - | |
✅* zephyr_unoq |
unoq
| 📗 | ✅* |
26.4% |
68 | 8 | - |
Legend
Board Test Status description 🔥 🔥 Test run failed to complete. ❌ 🔴 Test completed with unexpected errors. ✔️* 🚫 Test completed with errors, but all are known/expected. ✅* 🟡 Test completed with some warnings; no errors detected. ✅ 🟢 Test passed successfully, with no warnings or errors. 🌑 🌑 Test was skipped.
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Memory usage change @ 33dc317
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Problem
On Arduino Uno Q, calling analogWrite() on any pin silently returns without doing anything in two cases:
This causes analogWrite() to appear completely broken to users - no output, no error, no warning. The function just silently does nothing.
Root Cause
The pwm-pin-gpios mapping in the Uno Q device tree overlay is missing some pins (D0, D1, D4 are absent or commented out). This means pwm_pin_index() returns (size_t)-1 for those pins, which is always
Fix
Added a digitalWrite() fallback in both early-return paths:
This ensures analogWrite() always produces some output even when hardware PWM is unavailable, which is consistent with how other Arduino cores handle non-PWM pins.
Testing
Tested on Arduino Uno Q with:
Impact