Why Does My PIC18F87K22-I-PT Keep Resetting?

Why Does My PIC18F87K22-I/PT Keep Resetting? Troubleshooting and Solutions

If your PIC18F87K22-I/PT microcontroller keeps resetting, it can be frustrating. The resetting could be caused by a variety of factors, ranging from software issues to hardware problems. Let’s break down the potential causes and provide a step-by-step guide to resolve the issue.

Potential Causes for PIC18F87K22-I/PT Resetting

Power Supply Issues Cause: Inadequate or unstable power supply. Symptoms: Voltage drops or spikes that cause the microcontroller to reset. Watchdog Timer (WDT) Activation Cause: The Watchdog Timer might be enabled, and if it’s not cleared within the specified time, it will cause a reset. Symptoms: The device resets after a short period, particularly if the software is not keeping up with the WDT. Brown-Out Reset (BOR) Cause: If the supply voltage falls below the brown-out threshold, the microcontroller will reset to protect itself. Symptoms: Unexpected resets, especially after power fluctuations or when using batteries. Stack Overflow or Software Issues Cause: A software bug or stack overflow, where your program tries to access memory beyond what’s available. Symptoms: Random resets when the program executes certain parts of the code or when memory usage exceeds limits. Reset Pin Issue Cause: An external reset signal on the reset pin might be causing the microcontroller to reset unintentionally. Symptoms: Constant resetting when external components are connected to the reset pin. Noise or Interference Cause: Electrical noise or interference can trigger resets. Symptoms: Resets happening unpredictably, particularly when nearby motors or high-power devices are in use.

Step-by-Step Troubleshooting and Solutions

1. Check the Power Supply Action: Measure the voltage supplied to the PIC18F87K22-I/PT. Ensure it is within the specified range (usually 2V to 5.5V). Look for voltage dips or spikes that might trigger a reset. Solution: If the power supply is unstable, consider adding capacitor s (e.g., 100nF and 10µF) close to the power pins to smooth out the voltage. If using a battery, check if the voltage is dropping under load. 2. Disable or Manage the Watchdog Timer Action: Check if the WDT is enabled in your code. If the WDT is enabled, ensure that it’s regularly cleared with the ClrWdt() function in your code. Solution: If you don't need the WDT, disable it in the configuration bits to prevent it from resetting the microcontroller. If it’s required, make sure your software regularly resets the WDT before the timeout occurs. 3. Verify Brown-Out Reset (BOR) Settings Action: Check the BOR configuration in your code and hardware. Ensure that the BOR feature is set correctly and that the voltage threshold isn’t too low. Solution: If you're experiencing resets due to brown-out conditions, consider raising the brown-out threshold voltage to avoid resetting during small voltage drops. Alternatively, use a more stable power source or add a voltage regulator. 4. Debug Software Issues or Stack Overflow Action: Analyze your code for possible stack overflows or memory access errors. Check for recursive function calls or excessive memory usage. Solution: Use debugging tools such as MPLAB X IDE to check the stack usage. Optimize the code to reduce memory usage, avoid deep recursion, or increase stack size. Ensure all interrupts and timers are handled properly without causing conflicts. 5. Check the Reset Pin and External Components Action: Ensure the MCLR (Master Clear) pin is properly handled. If external components are connected to this pin, they may be causing unintended resets. If using an external reset circuit, ensure it’s correctly wired and not generating false resets. Solution: Pull the reset pin high through a pull-up resistor (e.g., 10kΩ) to prevent inadvertent resets. If the pin is not in use, it should be tied to the Vdd (positive supply voltage). 6. Minimize Electrical Noise and Interference Action: Look for sources of electrical noise, such as motors or other high-current devices. Check for spikes on the power supply lines or nearby traces. Solution: Use decoupling capacitors (e.g., 100nF ceramic) near the power pins to filter noise. If possible, move noisy components further away from the microcontroller.

Final Checklist

Power supply stability: Ensure a clean and stable voltage. Watchdog Timer: Disable or manage it correctly in the software. Brown-Out Reset settings: Verify the threshold and power conditions. Software debugging: Look for stack overflows or memory issues. Reset pin: Make sure it’s properly handled to avoid false resets. Electrical noise: Add decoupling capacitors and avoid interference.

By following this step-by-step guide, you should be able to identify the cause of your PIC18F87K22-I/PT resetting and implement the appropriate solutions to keep it running smoothly.