Fix DS18S20 broadcast conversion wait#294
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Global resolution also selects the broadcast conversion delay. Keep the requested resolution separate while programming configurable devices so fixed-resolution DS18S20 sensors retain their 750 ms wait. Constraint: DS18S20 is 9-bit but requires up to 750 ms to convert Rejected: Return 9 from getResolution | breaks established conversion timing Confidence: high Scope-risk: narrow Directive: Keep broadcast bitResolution at the slowest device on the bus Tested: WSL GCC 13 ASan/UBSan host bus harness; AVR GCC 7.3 atmega328p -Werror compile Not-tested: Physical mixed DS18S20 and DS18B20 bus
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Summary
Problem
A DS18S20 has a fixed 9-bit temperature register, but its maximum conversion time is 750 ms. The library intentionally returns 12 from the address-based
getResolution()as a conversion-time carrier for this reason (see #1, #4, and #174).setResolution(uint8_t)currently overwrites the globalbitResolutionwith the requested value and asks each address-based setter to skip global recalculation. AftersetResolution(9), a broadcastrequestTemperatures()therefore waits 94 ms even when a DS18S20 is on the bus. Address-based requests still wait 750 ms, so the two paths disagree.The change keeps the caller's requested value for configurable devices while restoring the global wait carrier to 12 when the scan encounters a DS18S20.
Validation
DallasTemperature.cppand reproduced global resolution 9 plus a 94 ms broadcast delay aftersetResolution(9)on a DS18S20 bus.DallasTemperature.cppcompiled foratmega328pwith AVR GCC 7.3,-Os -Wall -Wextra -Werror; RAM usage was unchanged.Not tested on a physical mixed-sensor bus.