WiFi reconnection fails permanently after connection attempt in low signal strength area fails #4461
Description
Hardware:
Board: Wemos Lonlin32 clone and ESP32-WROOM-32D module
Core Installation version: git master 1287c52
IDE name: Arduino IDE 1.8.13
Flash Frequency: 80Mhz
PSRAM enabled: no
Upload Speed: 921600
Computer OS: Fedora Linux 32
Description:
When using an ESP32 in an area of poor WiFi signal strength the connection is dropped as expected. When moving to a normal signal strength area the connection is not restored occasionally. I am seeing this behaviour with an AP hosted on a TP-Link TL-WDR3600 v1 using WPA2 PSK authentication. The only way to correct the situation is to restart the system which then connects immediately.
For low signal strength my AP is reporting -90dBm/-95dBm signal to noise (or out of contact completely). For normal signal strength the AP reports -32dBm/-95dBm signal to noise. Under normal signal strength the devices operate perfectly in high and low traffic operation.
It seems that there is something wrong in the WiFi connection state-machine somewhere and this behaviour is not as intended.
Sketch:
I am able to replicate with libraries/WiFi/examples/WiFiClientEvents/WiFiClientEvents.ino adding some additional logging in the main loop:
void loop()
{
delay(1000);
Serial.print( "WiFi status: ");
Serial.print( WiFi.status() );
Serial.print( " Address: " );
Serial.println( WiFi.localIP() );
}Debug Messages: (with Arduino debug level raised to Verbose)
...
[D][WiFiGeneric.cpp:374] _eventCallback(): Event: 5 - STA_DISCONNECTED
[W][WiFiGeneric.cpp:390] _eventCallback(): Reason: 201 - NO_AP_FOUND
[WiFi-event] event: 5
Disconnected from WiFi access point
WiFi lost connection. Reason: 201
WiFi status: 1 Address: 0.0.0.0
WiFi status: 1 Address: 0.0.0.0
[D][WiFiGeneric.cpp:374] _eventCallback(): Event: 5 - STA_DISCONNECTED
[W][WiFiGeneric.cpp:390] _eventCallback(): Reason: 4 - ASSOC_EXPIRE
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
WiFi status: 6 Address: 0.0.0.0
[D][WiFiGeneric.cpp:374] _eventCallback(): Event: 8 - STA_LOST_IP
[WiFi-event] event: 8
Lost IP address and IP address is reset to 0
WiFi status: 0 Address: 0.0.0.0
The final line repeats continuously even after moving to a high signal strength area.
The full log which includes several disconnect/reconnect events until the failure is exhibited can be found here:
ESP32-wifi-disconnect-reconnection-failure.log
Hack Fix / Work around
I have found it is possible to fix the problem by extending the WiFiEvent handler to force a disconnect and then reconnect.
case SYSTEM_EVENT_STA_LOST_IP:
Serial.println("Lost IP address and IP address is reset to 0");
WiFi.disconnect();
WiFi.reconnect();
break;