CBU Module with BK7231N: Prevent Sleep Mode for WiFi Connection

taggbricka wrote:

@ElektrodaBot CBU module with BK7231N goes to sleep after 6 seconds. not time enough to get on the WiFi net. How to recover it?

Initial Assessment of Available Information
From the details shared and the sample answers provided, it appears that your CBU module based on the BK7231N platform is entering a low-power (deep sleep) state roughly 6 seconds after powering up—too quickly for the module to make a stable Wi-Fi connection. Both offline and online answers agree that this behavior stems from the firmware’s power-saving (sleep) settings or from a watchdog timer configuration. The online answers point out the importance of adjusting deep sleep parameters and provide relevant resources regarding BK7231N deep sleep, wake-up, and firmware updates. Hence, the consensus is to modify the module’s firmware or configuration so that it remains awake long enough to establish a proper Wi-Fi link.

Below is a consolidated, detailed plan to help you recover the module and prevent it from sleeping before connecting to the network.

Direct Answer to the Question
To recover your BK7231N-based CBU module and prevent it from entering deep sleep after 6 seconds, you must either disable or extend the sleep timer in the firmware. This can be done by:
1. Using a suitable firmware flashing tool (e.g., bkWriter v1.60 or similar).
2. Changing the firmware settings to disable or delay sleep until after Wi-Fi is connected.
3. If accessible, using a console or configuration command (e.g., “setSleepMode 0” in OpenBeken) to keep the module awake during Wi-Fi initialization.

If you do not have direct firmware access, you may need to place the module in UART download mode (GPIO pin connection) or use specialized software to re-flash it with modified parameters.

Detailed Problem Analysis
1. Firmware Behavior
• The BK7231N chip is designed for low power applications and often ships with firmware configured to enter sleep quickly. For battery-powered devices, fast deep sleep is helpful; however, it can cause connectivity problems in scenarios that require immediate or consistent Wi-Fi access.
• Many custom or factory firmwares include a watchdog timer that triggers if the device fails to complete certain tasks (like connecting to Wi-Fi) within a limited window. If the watchdog or a deep sleep routine fires within 6 seconds, the module may never complete network initialization.

2. Potential Causes
• Out-of-the-box firmware with aggressive sleep defaults.
• Incorrect or incomplete firmware configurations (especially for modules re-flashed with OpenBeken, Tasmota, etc.).
• Unstable or insufficient power supply causing resets or fallback to low-power states.
• Incomplete or failing Wi-Fi connection attempts that lead the firmware to shut down the radio prematurely.

3. Approaches to Recovery
1. Check Power Supply
– Ensure the module consistently receives 3.3V, ideally from a regulator capable of delivering at least 300 mA peak current.
– Voltage drops during Wi-Fi initialization can cause restarts or unexpected behavior.

2. Access the Module Debug Interface
– Locate the UART pins (TX, RX, GND) on the module.
– Use a USB-to-serial adapter (e.g., CP2102, FT232) configured to the correct baud rate (often 115200) to monitor debug output.
– This output can indicate whether a watchdog or a sleep routine is triggering.

3. Modify the Firmware
a) If Using OpenBeken or Similar Custom Firmware
– Connect to the device console via serial or web, if you have enough time before sleep.
– Look for commands like “setSleepMode 0” (disabling sleep) or “setDeepSleepTime” (extending sleep delay).
– Save and reboot to lock in the new settings.
b) If Using Stock or Unknown Firmware
– You may need to re-flash custom firmware (e.g., OpenBeken or Tasmota).
– Utilize the BK7231N-specific flashing tools. Confirm you have the correct tool for BK7231N vs. BK7231T.
– Once re-flashed, configure deeper sleep parameters in the firmware.

4. Check Wi-Fi Configuration
– Confirm you are using 2.4 GHz Wi-Fi, as BK7231N does not support 5 GHz.
– Simplify the Wi-Fi SSID and password (avoid special characters that might cause parsing issues).
– Test with a mobile hotspot or dedicated access point to reduce complexity.

5. Reflash and Reset Strategy
– If the default method of connecting fails, force the module into “download” or “flash” mode by grounding the designated GPIO pin (often GPIO24 or similar for BK7231N boards) during power-up.
– Once in download mode, use a tool like bkWriter or the official BK7231N flash tool to erase or rewrite the firmware.
– After flashing, reconfigure your Wi-Fi details and sleep settings with caution.

Current Information and Trends
• Many IoT developers today are transitioning from earlier ESP8266/ESP32 modules to solutions like BK7231N for battery-focused devices because of the strong emphasis on low-power operation.
• Community-driven firmware like OpenBeken is increasingly popular for advanced configurations, letting you fine-tune wake and sleep durations to perfectly balance power consumption and connectivity reliability.

Supporting Explanations and Details
• On battery-powered devices (e.g., door sensors, PIR motion sensors), quick deep sleep is essential to extend battery life, but an overly short wake window can prevent normal operation.
• Adjusting deep sleep intervals can significantly impact battery usage, so find a suitable balance if your application is battery-powered. For mains-powered devices, you may disable deep sleep altogether.
• Custom firmware solutions typically provide command-line or web-based interfaces for adjusting deep sleep timers, which is often the easiest method to fix such issues without diving into C source code.

Practical Guidelines
1. Always confirm the correct flash tool version for your chip variant (BK7231N vs. BK7231T).
2. Back up the original firmware, if possible, in case you need to revert.
3. Start by fully disabling sleep mode to prove that the module can reliably connect; then, reintroduce longer sleep intervals if needed.
4. Observe caution when soldering or using test pins—some modules have small, delicate pads.

Possible Disclaimers or Additional Notes
• Modifying firmware can void warranties and requires some knowledge of hardware interfacing and firmware tools.
• Incorrect flashing procedures may brick the device.
• Exercise electrostatic discharge (ESD) protection when handling sensitive electronics.

Suggestions for Further Research
• Explore the Elektroda forum for project-specific guides on BK7231N deep sleep modifications, including example scripts and advanced troubleshooting logs.
• Investigate specialized low-power techniques, such as “wake on GPIO” or “wake on timer,” for battery-sensitive designs.
• Review how other community-based solutions (like Tasmota for BK7231N) handle agility between quick wake-up times and stable Wi-Fi connections.

Brief Summary
To prevent the BK7231N-based CBU module from sleeping within 6 seconds, you must override or disable its default deep sleep settings. Start with stable power, check UART logs to confirm if a watchdog or a timed sleep event is triggering, then adjust or re-flash the firmware to extend the wake window. Community-driven firmware solutions often have a single command (e.g., “setSleepMode 0”) that ensures the module remains active long enough to connect to Wi-Fi.

Questions for the User
1. Which firmware is currently running on your module—factory firmware, OpenBeken, Tasmota, or another?
2. Have you successfully used UART logging to see whether a watchdog or a specific sleep routine is cutting power?
3. Do you rely on battery power or a stable power supply? This affects how aggressively you might want to manage power consumption.
4. Would you be open to flashing a custom firmware if needed?

By clarifying these points, we can provide more targeted instructions to ensure a successful recovery and configuration of your BK7231N-based module.