Add Wire.setWireTimeout to avoid I2C bus hangs (closes #288) - #303
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If the I2C bus stops responding mid-transaction (noise, the display becomes disconnected, etc.), the underlying Wire library spins in an indefinite loop and the host MCU effectively hangs. The Arduino AVR core fixed this in ArduinoCore-avr@deea929 by exposing setWireTimeout(); cores that implement it define WIRE_HAS_TIMEOUT so callers can detect the feature at compile time. Use that detection: when periphBegin owns the wire->begin() call, follow it with a 25 ms timeout + reset on timeout. We only touch Wire's configuration when we performed the begin() ourselves; if the caller managed Wire externally, leave their configuration untouched. No behavioural change on cores without WIRE_HAS_TIMEOUT (the entire block is compiled out).
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ok! if it causes compilation issues in the future we may comment it out fyi |
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Thanks for the merge! Re: the future-compile-issue note — the Happy to send a follow-up if you ever want the timeout value made configurable instead of hard-coded to 25 ms. |
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Closes #288.
Scope of the change
Adafruit_SSD1306::begin()(I2C path) now follows thewire->begin()call withwire->setWireTimeout(25000, true)when the compiler can see that the Wire library exposes the timeout API (WIRE_HAS_TIMEOUTdefined).That's the only change — three lines of code plus a short comment, all behind a
#ifdef WIRE_HAS_TIMEOUTguard.Why
The Arduino AVR Wire library historically had no timeout: a noisy or disconnected I2C bus would put
TWIinto an indefinite loop and lock the entire sketch. This was tracked in ArduinoCore-avr#42 and fixed by ArduinoCore-avr@deea929, which addedsetWireTimeout(uint32_t us, bool reset_with_timeout)and theWIRE_HAS_TIMEOUTfeature macro.The Adafruit_SSD1306 library never adopted the new API, so users on AVR cores still get hangs on SDA/SCL noise or display disconnect. Issue #288 asked for that.
Limitations
begin()path is touched. SPI is unchanged.periphBeginistrue— i.e. when this library performedwire->begin()itself. If the caller already calledWire.begin()(theperiphBegin=falsepath), their Wire configuration is left untouched on the assumption they're managing it explicitly.WIRE_HAS_TIMEOUT(older AVR cores, some non-AVR cores) compile out the entire block — no behavioural change there.Tests run locally
python3 ci/run-clang-format.py --clang-format-executable clang-format -e 'ci/*' -e 'bin/*' Adafruit_SSD1306.cpp→ cleanMaintainer signal
Per @ladyada's comment on #288: "ok can you submit a simple PR that passes CI?" — happy to iterate if anything here needs adjusting.