ESP32 Wi-Fi Issues: Debugging Intermittent Failures

by Alex Johnson 52 views

Experiencing intermittent Wi-Fi connection failures on your ESP32? You're not alone. This article delves into a perplexing issue where ESP32 devices, particularly the ESP32-C6, encounter random disconnects despite having the correct Wi-Fi credentials. This issue, potentially stemming from a race condition within the Wi-Fi connection process, can be a significant hurdle in project development. We'll break down the problem, analyze the root causes, and explore potential solutions.

Understanding the Problem: Intermittent Wi-Fi Woes

Intermittent Wi-Fi connection problems on the ESP32 platform can be incredibly frustrating. Imagine your smart home device randomly losing connection, disrupting its functionality and requiring manual intervention. This is precisely the scenario many developers face with the ESP32, especially when using the ESP-IDF v5.3 framework. The core issue manifests as a failure to connect to the Wi-Fi network despite providing the correct SSID and passphrase. The device may report a kNetworkNotFound error, even though the network is indeed available and the credentials are accurate.

This issue is distinct from authentication failures (where incorrect credentials lead to a kAuthFailure error). Instead, it appears to be a more fundamental problem in the connection establishment process itself. The randomness of the failures, occurring in roughly one out of six attempts, suggests a potential race condition – a situation where the outcome of the program depends on the unpredictable order in which different parts of the code execute.

Reproduction Steps: Setting the Stage for Failure

To understand and address this issue, it's crucial to be able to reproduce it consistently. The following steps outline a process for triggering the intermittent Wi-Fi connection failures on an ESP32-C6 device:

  1. Environment Setup: Begin by setting up the ESP-IDF v5.3 development environment. This involves cloning the ESP-IDF repository, installing the necessary tools, and configuring the environment variables. The official ESP-IDF documentation provides comprehensive instructions for this process.

    mkdir ~/esp
cd ~/esp
git clone -b v5.3 --recursive --depth 1 --shallow-submodule https://github.com/espressif/esp-idf.git
cd ~/esp/esp-idf
./install.sh

  2. Project Preparation: Navigate to the connectedhomeip project directory and activate the development environment. This typically involves sourcing the bootstrap.sh and activate.sh scripts.

    source scripts/bootstrap.sh
source scripts/activate.sh
python3 -m pip install esptool

  3. Environment Configuration: Configure the ESP-IDF environment by sourcing the export.sh script from the ESP-IDF directory and reactivating the environment.

    source ../esp/esp-idf/export.sh
source scripts/activate.sh

  4. Target and Build: Set the target device to ESP32-C6 and build the all-clusters-app example project. You might need to adjust the partition table in partitions.csv to accommodate OTA updates.

    idf.py -C examples/all-clusters-app/esp32 esp32c6
idf.py -C examples/all-clusters-app/esp32 build

  5. Flashing: Flash the compiled firmware onto the ESP32-C6 device using the idf.py flash command. Monitor the process using the idf.py monitor command.

    idf.py -C examples/all-clusters-app/esp32 -p /dev/tty.usbserial-140 flash monitor

  6. Testing: In a separate terminal, execute the TC_CNET_4_23.py test script, providing the correct Wi-Fi SSID, passphrase, discriminator, and passcode.

    python src/python_testing/TC_CNET_4_23.py --in-test-commissioning-method ble-wifi --wifi-ssid <WIFI_SSID> --wifi-passphrase <WIFI_PASSPHRASE> --discriminator 3840 --passcode 20202021 --endpoint 0

By following these steps, you can reliably reproduce the intermittent Wi-Fi connection failures and observe the kNetworkNotFound error during Step 13 of the test script.

Observed Behavior: A Glimpse into the Failure

When the ConnectNetwork command is sent to the ESP32 device, the logs reveal a series of events that lead to the connection failure. The device attempts to connect to the Wi-Fi network, but the process is interrupted by errors. Specifically, the logs show the following:

[0;32mI (123702) chip[EM]: >>> [E:14321r S:64064 M:248026995] (S) Msg RX from 1:FFFFFFFB00000000 [62ED] to 0000000000000000 --- Type 0001:08 (IM:InvokeCommandRequest) (B:85) [0m
[0;32mI (123722) chip[NP]: ESP NetworkCommissioningDelegate: SSID: MovistarFibra-B1FB50 [0m
[0;32mI (123732) chip[DL]: WiFi station mode change: Enabled -> Disabled [0m
[0;32mI (123752) chip[DL]: WiFi station mode change: Disabled -> Enabled [0m
[0;32mI (123762) chip[DL]: Attempting to connect WiFi station interface [0m
[0;32mI (123762) chip[DL]: Done driving station state, nothing else to do... [0m
[0;32mI (123772) chip[DL]: Attempting to connect WiFi station interface [0m
[1;31mE (123782) wifi:sta is connecting, return error [0m
[0;31mE (123782) chip[DL]: esp_wifi_connect() failed: ESP_ERR_WIFI_CONN [0m
[0;32mI (123782) chip[DL]: Attempting to connect WiFi station interface [0m
[1;31mE (123792) wifi:sta is connecting, return error [0m
[0;31mE (123792) chip[DL]: esp_wifi_connect() failed: ESP_ERR_WIFI_CONN [0m
[0;32mI (126202) NimBLE: GATT procedure initiated: indicate;  [0m
[0;32mI (126202) NimBLE: att_handle=18

The key observation here is that the device makes three rapid calls to esp_wifi_connect() within a short 30ms window. The second and third attempts are rejected because a connection is already in progress, leading to the ESP_ERR_WIFI_CONN error. This suggests a potential race condition where multiple connection attempts are initiated before the previous one has completed.

Root Cause Analysis: Unraveling the Mystery

To pinpoint the root cause, let's dissect the code execution flow within the ESP32's Wi-Fi connection logic. The analysis focuses on two key areas:

1. The ConnectWiFiNetwork Method

Digging into the ConnectNetwork method in src/platform/ESP32/NetworkCommissioningDriver.cpp, we find a sequence of calls that are crucial to understanding the problem.

  • The method initiates the Wi-Fi connection process by calling ConnectWiFiNetwork.
  • It then appears to start a connection timer, likely to monitor the connection attempt and handle timeouts.
  • Inside ConnectWiFiNetwork, there are calls to SetWiFiStationMode(ConnectivityManager::kWiFiStationMode_Disabled) twice (lines 246 and 263), followed by a call to SetWiFiStationMode(ConnectivityManager::kWiFiStationMode_Enabled) (line 264).

The duplicate call to SetWiFiStationMode(Disabled) on line 263 is a potential red flag, as it might be interfering with the connection process.

2. The SetWiFiStationMode Method and DriveStationState

The SetWiFiStationMode method in src/platform/ESP32/ConnectivityManagerImpl_Wifi.cpp schedules the execution of DriveStationState. This function is responsible for managing the Wi-Fi station mode and initiating the connection to the access point.

Within DriveStationState, the code checks if the station interface is already connected. If not, it proceeds to connect, but only if mLastStationConnectFailTime is either zero or the current time is after mLastStationConnectFailTime + mWiFiStationReconnectInterval. Herein lies a critical issue: mLastStationConnectFailTime is not updated before calling esp_wifi_connect(). This means that if multiple calls to DriveStationState occur in rapid succession, the condition might always evaluate to true, leading to multiple connection attempts.

These rapid connection attempts, triggered by the duplicate SetWiFiStationMode(Disabled) call and the lack of mLastStationConnectFailTime update, can overwhelm the Wi-Fi stack and cause the ESP_ERR_WIFI_CONN error.

The Two Culprits

In summary, the intermittent Wi-Fi connection failures appear to stem from the following two issues working in tandem:

  1. Duplicate Call to SetWiFiStationMode(Disabled): The redundant call in NetworkCommissioningDriver.cpp might be disrupting the Wi-Fi state management.
  2. mLastStationConnectFailTime Not Updated: The failure to update the timestamp before calling esp_wifi_connect() in ConnectivityManagerImpl_WiFi.cpp allows for multiple rapid connection attempts.

Proposed Solution: A Multi-pronged Approach

Addressing this complex issue requires a two-pronged strategy that targets both identified problems:

  1. Remove the Redundant Call: Eliminate the duplicate call to SetWiFiStationMode(Disabled) on line 263 in NetworkCommissioningDriver.cpp. This should prevent the scheduling of unnecessary DriveStationState calls.

  2. Update mLastStationConnectFailTime: Modify ConnectivityManagerImpl_WiFi.cpp to update mLastStationConnectFailTime before calling esp_wifi_connect() within DriveStationState. This will ensure that subsequent connection attempts are throttled, preventing the Wi-Fi stack from being overwhelmed.

By implementing these changes, the likelihood of multiple rapid connection attempts should be significantly reduced, leading to a more stable and reliable Wi-Fi connection on the ESP32 platform.

Conclusion: Towards Robust Wi-Fi Connectivity

Intermittent issues can be among the most challenging to debug, but by meticulously analyzing logs and code, we can often uncover the root causes. In this case, a combination of a redundant function call and a missing timestamp update appears to be responsible for the ESP32's Wi-Fi woes. By addressing these issues, developers can build more reliable and robust connected devices.

For further reading on ESP32 and Wi-Fi connectivity, you may find valuable information on the Espressif Documentation website.