From 3086bb2d52609c7fa1fc513ca9cd0ad7de93a365 Mon Sep 17 00:00:00 2001
From: 94xhn <87560781+94xhn@users.noreply.github.com>
Date: Tue, 14 Jul 2026 14:31:32 +0800
Subject: [PATCH] fix: preserve DS18S20 broadcast wait

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
---
 DallasTemperature.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/DallasTemperature.cpp b/DallasTemperature.cpp
index 29b7bc5..25882b2 100644
--- a/DallasTemperature.cpp
+++ b/DallasTemperature.cpp
@@ -318,12 +318,15 @@ float DallasTemperature::getTempFByIndex(uint8_t index) {
 }
 
 void DallasTemperature::setResolution(uint8_t newResolution) {
-    bitResolution = constrain(newResolution, 9, 12);
+    newResolution = constrain(newResolution, 9, 12);
+    bitResolution = newResolution;
     DeviceAddress deviceAddress;
     _wire->reset_search();
     for (uint8_t i = 0; i < devices; i++) {
         if (_wire->search(deviceAddress) && validAddress(deviceAddress)) {
-            setResolution(deviceAddress, bitResolution, true);
+            setResolution(deviceAddress, newResolution, true);
+            // DS18S20 is fixed at 9-bit but needs the 12-bit conversion delay.
+            if (deviceAddress[0] == DS18S20MODEL) bitResolution = 12;
         }
     }
 }
@@ -815,4 +818,4 @@ int16_t DallasTemperature::getUserDataByIndex(uint8_t deviceIndex) {
     DeviceAddress deviceAddress;
     getAddress(deviceAddress, deviceIndex);
     return getUserData((uint8_t*)deviceAddress);
-}
\ No newline at end of file
+}