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Fix LEDs glitching at startup (ESP32 only) #5337

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Merged
DedeHai merged 7 commits into from
Feb 20, 2026
Merged

Fix LEDs glitching at startup (ESP32 only) #5337

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33a12f9
fix bootup output glitch by using NVM stored credentials
DedeHai Feb 1, 2026
00da21f
fix race condition
DedeHai Feb 1, 2026
c092c6f
fix typo
DedeHai Feb 1, 2026
cea77f9
add ifdef guards for ESP8266
DedeHai Feb 2, 2026
386b703
revert whitespace change
DedeHai Feb 2, 2026
2cbc7c6
clear intention on union access
DedeHai Feb 2, 2026
4778972
Merge branch 'main' into bootup_wifiglitchfix
DedeHai Feb 20, 2026
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28 changes: 27 additions & 1 deletion wled00/wled.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -507,7 +507,7 @@ void WLED::setup()
#ifndef ESP8266
WiFi.setScanMethod(WIFI_ALL_CHANNEL_SCAN);
#endif
WiFi.persistent(false);
WiFi.persistent(false); // note: on ESP32 this is only applied if WiFi.mode() is called and only if mode changes, use low level esp_wifi_set_storage() to change storage method immediately
WiFi.onEvent(WiFiEvent);
WiFi.mode(WIFI_STA); // enable scanning
findWiFi(true); // start scanning for available WiFi-s
Expand Down Expand Up @@ -670,6 +670,27 @@ void WLED::initAP(bool resetAP)

void WLED::initConnection()
{
#ifdef ARDUINO_ARCH_ESP32
static bool firstCall = true;
bool updateWiFiNVM = false;
if (firstCall) {
// check cached WiFi config in flash, esp_wifi_get_config still contains NVM values at this point
// note: connecting to the NVM stored wifi is much faster and prevents boot-up glitches on LEDs (there is no benefit on ESP8266)
wifi_config_t cachedConfig;
esp_err_t configResult = esp_wifi_get_config( (wifi_interface_t)ESP_IF_WIFI_STA, &cachedConfig );
if( configResult == ESP_OK ) {
if (strncmp((const char*)cachedConfig.sta.ssid, multiWiFi[0].clientSSID, 32) != 0 ||
strncmp((const char*)cachedConfig.sta.password, multiWiFi[0].clientPass, 64) != 0) {
Comment on lines +682 to +683
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⚠️ Potential issue | 🟡 Minor

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Find WiFiConfig struct definition
find . -name "*.h" -o -name "*.cpp" | head -20
rg -n "struct WiFiConfig" -A 20 --type cpp --type h

Repository: wled/WLED

Length of output: 2112

🏁 Script executed:

#!/bin/bash
# Search for clientSSID and clientPass declarations
rg -n "clientSSID|clientPass" --type cpp --type h -B 1 -A 1 | head -50

Repository: wled/WLED

Length of output: 3274

🏁 Script executed:

#!/bin/bash
# Look for defined constants that might correspond to 32 or 64
rg -n "#define.*32|#define.*64" --type h | head -30
rg -n "const.*32|const.*64" --type cpp --type h | head -30

Repository: wled/WLED

Length of output: 5516

🏁 Script executed:

#!/bin/bash
# Find where cachedConfig is defined to understand its structure
rg -n "cachedConfig" wled00/wled.cpp -B 2 -A 2 | head -40

Repository: wled/WLED

Length of output: 828

🏁 Script executed:

#!/bin/bash
# Verify the ESP-IDF wifi_sta_config_t sizes mentioned in the review
# Check if WLED uses ESP-IDF types or defines its own
rg -n "wifi_sta_config_t" wled00/ --type cpp -B 1 -A 1

Repository: wled/WLED

Length of output: 35

🏁 Script executed:

#!/bin/bash
# Check the actual buffer sizes used in other parts of code
rg -n "clientSSID\[|clientPass\[" wled00/ --type cpp --type h

Repository: wled/WLED

Length of output: 304

Use sizeof() instead of hardcoded buffer sizes in strncmp calls.

The hardcoded 32 and 64 at lines 682–683 correspond to the ESP-IDF wifi_sta_config_t.ssid[32] and .password[64] field sizes. Using sizeof(cachedConfig.sta.ssid) and sizeof(cachedConfig.sta.password) is more maintainable and makes the intent explicit. The WLED WiFiConfig buffers (clientSSID[33] and clientPass[65]) have sufficient capacity to hold the data.

Additionally, fix the if( spacing at line 681 (should be if () to match the style of surrounding code.

♻️ Proposed fix 
-    if( configResult == ESP_OK ) {
-      if (strncmp((const char*)cachedConfig.sta.ssid, multiWiFi[0].clientSSID, 32) != 0 ||
-      strncmp((const char*)cachedConfig.sta.password, multiWiFi[0].clientPass, 64) != 0) {
+    if (configResult == ESP_OK) {
+      if (strncmp((const char*)cachedConfig.sta.ssid, multiWiFi[0].clientSSID, sizeof(cachedConfig.sta.ssid)) != 0 ||
+          strncmp((const char*)cachedConfig.sta.password, multiWiFi[0].clientPass, sizeof(cachedConfig.sta.password)) != 0) {
🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@wled00/wled.cpp` around lines 682 - 683, Replace hardcoded lengths in the
strncmp checks with sizeof on the ESP-IDF config fields: use
sizeof(cachedConfig.sta.ssid) and sizeof(cachedConfig.sta.password) when
comparing cachedConfig.sta.ssid/password to multiWiFi[0].clientSSID and
multiWiFi[0].clientPass via strncmp; also correct the spacing of the conditional
to "if (" to match surrounding style. Ensure you only change the arguments to
strncmp and the if( spacing—leave function names and array indexes
(cachedConfig, multiWiFi[0]) unchanged.

updateWiFiNVM = true; // SSID or pass changed, update NVM at next WiFi.begin() call
DEBUG_PRINTLN(F("WiFi config NVM update triggered"));
}
}
firstCall = false;
}
else
esp_wifi_set_storage(WIFI_STORAGE_RAM); // do not update NVM credentials while running to prevent wear on flash
#endif

DEBUG_PRINTF_P(PSTR("initConnection() called @ %lus.\n"), millis()/1000);
#ifdef WLED_ENABLE_WEBSOCKETS
ws.onEvent(wsEvent);
Expand Down Expand Up @@ -720,6 +741,11 @@ void WLED::initConnection()
char hostname[25];
prepareHostname(hostname);

#ifdef ARDUINO_ARCH_ESP32
if(updateWiFiNVM && selectedWiFi == 0) // NVM only can store one wifi: store credentials of first WiFi even if multiple are configured
esp_wifi_set_storage(WIFI_STORAGE_FLASH); // temporary override WiFi.persistent(false) to store credentials in flash (is reset to RAM on next initConnection() call)
#endif

#ifdef WLED_ENABLE_WPA_ENTERPRISE
if (multiWiFi[selectedWiFi].encryptionType == WIFI_ENCRYPTION_TYPE_PSK) {
DEBUG_PRINTLN(F("Using PSK"));
Expand Down