Why the LPC1778FBD208 K Keeps Resetting – Common Causes and Fixes
If you're working with the LPC1778FBD208K microcontroller and facing issues where the system keeps resetting, you're not alone. This kind of behavior can be caused by a variety of factors. Let’s break down the common causes and provide easy-to-follow steps to help you resolve this problem.
1. Power Supply Issues
One of the most common causes of random resets in microcontrollers is an unstable or insufficient power supply. If the voltage provided to the LPC1778FBD208K fluctuates or drops below the required threshold, the device may reset to protect itself.
Possible Symptoms:
Unexpected resets during operation. Resetting during specific tasks or operations.Solution:
Check the Power Supply: Ensure that your power source provides stable and adequate voltage (typically 3.3V for the LPC1778). Use a capacitor : Add a decoupling capacitor (typically 100nF) close to the power pins of the microcontroller to smooth out any voltage spikes or dips. Measure Voltage: Use a multimeter to measure the supply voltage and confirm it's consistent during operation.2. Watchdog Timer (WDT) Timeout
The LPC1778 has an integrated watchdog timer (WDT) that is designed to reset the microcontroller if the software becomes unresponsive. If the WDT is not properly serviced (i.e., not being reset periodically), it will cause the system to reset.
Possible Symptoms:
Resets happening at regular intervals, especially after long periods of operation.Solution:
Check Watchdog Timer Settings: Review your software to ensure you are resetting the watchdog timer within the proper intervals. If your application requires long processing periods, consider disabling the WDT or increasing the timeout period. Properly Feed the Watchdog: In your main loop or critical sections, ensure that the watchdog timer is periodically reset, usually with a dedicated function like wdt_feed() or similar.3. Brown-Out Detection (BOD)
The LPC1778 includes brown-out detection circuitry, which will reset the device if the supply voltage drops below a critical threshold. This helps prevent improper operation but can also cause resets if the power supply is unstable or just below the BOD threshold.
Possible Symptoms:
Resets happening when voltage supply fluctuates or right after power-up.Solution:
Disable BOD (If Appropriate): If your application requires a very stable power source and you’re certain that the voltage won't dip below the threshold, you can disable the brown-out detection in your firmware. This can be done by configuring the BOD threshold or disabling it entirely in the system control registers. Use a Stable Power Supply: Ensure your power source is capable of providing a stable voltage without fluctuations. If necessary, use a regulated power supply.4. External Interrupts or Peripheral Misconfiguration
Misconfigured interrupts or peripheral devices can also cause the LPC1778 to reset. Incorrect settings in the peripherals or interrupts might trigger unintended resets.
Possible Symptoms:
Resets happen when certain peripherals or interrupts are activated. Unexpected resets during communication with external devices.Solution:
Review Interrupt Settings: Check your interrupt vectors and ensure that you are not triggering an interrupt in an uncontrolled way that might lead to a reset. Check Peripheral Configurations: Review the setup for peripherals such as UART, SPI, or timers, and verify that they are configured correctly. Ensure that the peripherals are not causing resource conflicts or resetting the MCU due to improper setup.5. Software Bugs or Stack Overflow
Bugs in the application code, such as accessing invalid Memory or causing a stack overflow, could lead to unexpected resets. These issues might not always be obvious but can cause the MCU to enter an unstable state, triggering a reset.
Possible Symptoms:
Random resets, especially after specific functions or operations are executed. Stack overflows, memory corruption, or crashes.Solution:
Enable Debugging: Use a debugger to step through the code and check for anomalies. Look for possible memory overflows or invalid memory access. Increase Stack Size: If you're running into stack overflow issues, try increasing the stack size in the linker settings or in your startup code. Check Memory Bounds: Review the usage of arrays and buffers to ensure that you are not exceeding their allocated space.6. External Reset Pin Trigger
The LPC1778FBD208K has an external reset pin that can trigger a reset if it is pulled low. A floating reset pin, or one that is accidentally connected to ground, can cause repeated resets.
Possible Symptoms:
Frequent resets without obvious cause.Solution:
Check Reset Pin Connection: Ensure that the external reset pin (usually labeled RESET or NRST) is properly handled. If not being used, ensure it is either connected to a high voltage (through a pull-up resistor) or correctly managed. Verify External Circuitry: If external circuits (like buttons or other logic) are connected to the reset pin, check their design to avoid unintended low logic levels that might trigger resets.7. Firmware or Bootloader Issues
Finally, a bug in the bootloader or firmware that runs on startup could cause the system to repeatedly reset. For example, if the bootloader cannot load the main application due to misconfiguration, it might reset the MCU.
Possible Symptoms:
Continuous resetting on power-up. The system doesn’t load the application as expected.Solution:
Reflash the Bootloader/Firmware: Reprogram the bootloader and application firmware to ensure that the system starts correctly. Check Boot Configuration: Verify the boot configuration settings in the microcontroller's control registers to ensure that it is loading the correct firmware and not getting stuck in an invalid state.Conclusion
When the LPC1778FBD208K keeps resetting, the cause is often related to power supply issues, watchdog timer misconfiguration, or peripheral faults. By following the above troubleshooting steps, you should be able to identify and resolve the issue. Ensure that your power supply is stable, your software correctly handles watchdogs and interrupts, and your microcontroller’s settings are appropriately configured to prevent unwanted resets.