Why PIC16F690-I-SS is Not Responding to Interrupts: Troubleshooting Guide

Why PIC16F690-I/SS is Not Responding to Interrupts: Troubleshooting Guide

If you are working with the PIC16F690-I/SS microcontroller and facing an issue where it does not respond to interrupts, don’t worry—this guide will walk you through common reasons and troubleshooting steps to resolve the issue effectively.

1. Interrupts Not Enabled

Problem: One of the most common reasons your PIC16F690-I/SS isn't responding to interrupts is that the interrupt system itself might not be enabled.

Solution: Ensure that global and peripheral interrupts are enabled.

Global Interrupt Enable (GIE): Set the GIE bit in the INTCON register.

Peripheral Interrupt Enable (PEIE): Set the PEIE bit in the INTCON register.

Peripheral Interrupt Enable (for specific interrupt sources): Enable the corresponding interrupt in the peripheral’s control register.

Example:

INTCONbits.GIE = 1; // Enable Global Interrupt INTCONbits.PEIE = 1; // Enable Peripheral Interrupt

2. Interrupt Source Disabled

Problem: The interrupt source itself might not be enabled or properly configured. Solution: Double-check that the interrupt source (like TMR0, external pin change, etc.) is enabled in the appropriate control register for that peripheral. For instance, for TMR0 interrupt, make sure: c INTCONbits.TMR0IE = 1; // Enable TMR0 interrupt For External Interrupt (INT), ensure that the INT0IE bit is set: c INTCONbits.INT0IE = 1; // Enable External Interrupt

3. Interrupt Flag Not Cleared

Problem: Interrupts may not be triggering if the interrupt flag for the specific interrupt source isn't cleared properly. Solution: After the interrupt service routine (ISR) executes, clear the interrupt flag in the respective register. For TMR0 interrupt: c INTCONbits.TMR0IF = 0; // Clear TMR0 interrupt flag For External Interrupt (INT0): c INTCONbits.INT0IF = 0; // Clear external interrupt flag

4. Interrupt Priority Not Set

Problem: If you are using priority-level interrupts, the priority level might be incorrectly configured, causing the interrupt to be masked.

Solution: Ensure that you correctly set the interrupt priorities in the IPEN and priority bits.

For high-priority interrupts, set the IPEN bit in the RCON register.

Ensure you set the appropriate priority for the interrupt source in the peripheral’s register.

Example:

RCONbits.IPEN = 1; // Enable priority-level interrupts

5. Incorrect Interrupt Vector

Problem: Your microcontroller might be directing interrupts to the wrong interrupt vector if the interrupt vectors are not configured properly. Solution: Make sure the interrupt vector addresses are set correctly for your application. Review the datasheet for the appropriate vectors.

6. Global Interrupt Flag Not Set

Problem: The global interrupt enable bit (GIE) in the INTCON register is not set, which disables all interrupts. Solution: Set the GIE bit to 1 to globally enable interrupts: c INTCONbits.GIE = 1; // Enable global interrupt flag

7. Low Power Mode (SLEEP Mode)

Problem: If the PIC16F690-I/SS is in SLEEP mode, it may not respond to interrupts.

Solution: If you want interrupts to be recognized while the device is in low power mode, you must ensure that the SLEEP mode is disabled, or at least enable the appropriate wake-up interrupts.

You can also use the sleep mode in a controlled manner, ensuring that the MCU only sleeps when it's necessary.

Example:

SLEEP(); // Enter sleep mode

8. Incorrect Oscillator Configuration

Problem: If the microcontroller is not configured to use the correct oscillator, it might not operate as expected, affecting interrupt timing.

Solution: Verify that the oscillator settings in the configuration bits are correct and that the device is operating with the correct clock source.

Example:

__CONFIG(0x3FF6); // Example for configuring oscillator settings

9. Faulty External Interrupt Pin

Problem: If you're using an external interrupt pin, it might be incorrectly configured or connected. Solution: Check the wiring of the interrupt pin (e.g., INT0 pin) to ensure that it’s connected properly to the hardware and set up to trigger the correct edge (rising/falling). Example of configuring an external interrupt pin: c TRISBbits.TRISB0 = 1; // Set RB0 as input for external interrupt INTCONbits.INT0IE = 1; // Enable INT0 interrupt

10. Faulty Interrupt Service Routine (ISR)

Problem: The ISR might not be correctly implemented or may contain errors, preventing the interrupt from being processed.

Solution: Double-check that your ISR is correctly written and that the interrupt is serviced promptly. Also, ensure that the return from interrupt (RETI) instruction is used properly.

Example:

void __interrupt() ISR(void) { // ISR code INTCONbits.INT0IF = 0; // Clear interrupt flag }

Conclusion

By following this troubleshooting guide step by step, you should be able to identify and fix the issue with interrupts not working on your PIC16F690-I/SS microcontroller. Always ensure that the interrupt system is enabled, sources are configured properly, flags are cleared, and the ISR is correctly written. If these checks are followed thoroughly, your interrupt handling should function as expected.