Write a program for the MSP430 using Energia placing an interrupt on the push 2

Question

Write a program for the MSP430 using Energia placing an interrupt on the push 2 button so that the first time the button is pushed the red LED should turn on for 1 second and then turn off. The second time the button is pushed the red LED should turn on for 1 second, turn off for 1 second, turn back on for 1 second, and off again. The third time the button is pushed the green LED should turn on for 1 second and then turn off. The fourth time the button is pushed the green LED should turn on for 1 second, turn off for 1 second, turn back on for 1 second, and off again. The fifth time the button is pushed the red LED should turn on for 1 second and then turn off. The sixth time the button is pushed the red LED should turn on for 1 second, turn off for 1 second, turn back on for 1 second, and off again…. (Etc. etc. etc.)

Explanation / Answer

/* This code demonstrates the use of both switches, labelled S1 (RESET) and S2 (P1.3) on the MSP430 Launchpad. * The code implements a software debounce using the WDT and also indicates a long press i.e. switch pressed * for more than 1.5 seconds * Switch S1 uses the RST/NMI pin as an input * Switch S2 uses the P1.3 general purpose I/O pin * The P1.0 Red LED1 is used to indicate when S2 (P1.3) is pressed (Active Pressed). * The P1.6 Green LED2 is used to indicate when S1 (RESET) is pressed (Active Pressed). * These LEDs are turned off when the switches are released. * The Watchdog Timer (WDT) is used both to debounce the switches and to time the length of the press. The debounce * is achieved by using the delay provided by the WDT to re-enable the Switch interrupts only after the bouncing has * finished. The WDT interrupt service routine also increments separate counters (one for each switch) when the * switches are pressed. When the count exceeds a certain time the P1.0 LED (for Switch 1) and the P1.6 LED (for * Switch 2) are turned on to indicate a long press. * In order to run the code using the RESET pin as a switch input you need to cycle the power on the LaunchPad. */ #include #define FLIP_HOLD (0x3300 | WDTHOLD) // flip HOLD while preserving other bits #define S1 0x0001 #define S2 0x0002 unsigned char PressCountS1 = 0; unsigned char PressCountS2 = 0; unsigned char Pressed = 0; unsigned char PressRelease = 0; void InitialiseSwitch2(void); void main (void) { WDTCTL = WDTPW + WDTHOLD; // Stop WDT P1DIR |= (BIT0|BIT6); // Set the LEDs on P1.0, P1.1, P1.2 and P1.6 as outputs P1OUT = 0; P1OUT |= (BIT0|BIT6); // Turn on P1.0 and P1.6 LEDs to indicate initial state InitialiseSwitch2(); // Initialise Switch 2 which is attached to P1.3 // The Watchdog Timer (WDT) will be used to debounce s1 and s2 WDTCTL = WDTPW | WDTHOLD | WDTNMIES | WDTNMI; //WDT password + Stop WDT + detect RST button falling edge + set RST/NMI pin to NMI IFG1 &= ~(WDTIFG | NMIIFG); // Clear the WDT and NMI interrupt flags IE1 |= WDTIE | NMIIE; // Enable the WDT and NMI interrupts // The CPU is free to do other tasks, or go to sleep __bis_SR_register(LPM0_bits | GIE); } /* This function configures the button so it will trigger interrupts * when pressed. Those interrupts will be handled by PORT1_ISR() */ void InitialiseSwitch2(void) { P1DIR &= ~BIT3; // Set button pin as an input pin P1OUT |= BIT3; // Set pull up resistor on for button P1REN |= BIT3; // Enable pull up resistor for button to keep pin high until pressed P1IES |= BIT3; // Enable Interrupt to trigger on the falling edge (high (unpressed) to low (pressed) transition) P1IFG &= ~BIT3; // Clear the interrupt flag for the button P1IE |= BIT3; // Enable interrupts on port 1 for the button } // isr to detect make/break of s1 at the nRST/NMI pin // Note the occurrence of an NMI interrupt automatically disables the NMI interrupt enable. #pragma vector = NMI_VECTOR __interrupt void nmi_isr(void) { if (IFG1 & NMIIFG) // Check if NMI interrupt was caused by nRST/NMI pin { IFG1 &= ~NMIIFG; // clear NMI interrupt flag if (WDTCTL & WDTNMIES) // falling edge detected { P1OUT |= BIT6; // Turn on P1.0 red LED to indicate switch 1 is pressed Pressed |= S1; // Set Switch 2 Pressed flag PressCountS1 = 0; // Reset Switch 2 long press count WDTCTL = WDT_MDLY_32 | WDTNMI; // WDT 32ms delay + set RST/NMI pin to NMI // Note: WDT_MDLY_32 = WDTPW | WDTTMSEL | WDTCNTCL // WDT password + Interval mode + clear count // Note: this will also set the NMI interrupt to trigger on the rising edge } else // rising edge detected { P1OUT &= ~(BIT6+BIT0); // Turn off P1.6 and P1.0 LEDs Pressed &= ~S1; // Reset Switch 1 Pressed flag PressRelease |= S1; // Set Press and Released flag WDTCTL = WDT_MDLY_32 | WDTNMIES | WDTNMI; // WDT 32ms delay + falling edge + set RST/NMI pin to NMI } } // Note that NMIIE is now cleared; the wdt_isr will set NMIIE 32ms later else {/* add code here to handle other kinds of NMI, if any */} } #pragma vector=PORT1_VECTOR __interrupt void PORT1_ISR(void) { if (P1IFG & BIT3) { P1IE &= ~BIT3; // Disable Button interrupt to avoid bounces P1IFG &= ~BIT3; // Clear the interrupt flag for the button if (P1IES & BIT3) { // Falling edge detected P1OUT |= BIT0; // Turn on P1.0 red LED to indicate switch 2 is pressed Pressed |= S2; // Set Switch 2 Pressed flag PressCountS2 = 0; // Reset Switch 2 long press count } else { // Rising edge detected P1OUT &= ~(BIT0+BIT6); // Turn off P1.0 and P1.6 LEDs Pressed &= ~S2; // Reset Switch 2 Pressed flag PressRelease |= S2; // Set Press and Released flag } P1IES ^= BIT3; // Toggle edge detect IFG1 &= ~WDTIFG; // Clear the interrupt flag for the WDT WDTCTL = WDT_MDLY_32 | (WDTCTL & 0x007F); // Restart the WDT with the same NMI status as set by the NMI interrupt } else {/* add code here to handle other PORT1 interrupts, if any */} } // WDT is used to debounce s1 and s2 by delaying the re-enable of the NMIIE and P1IE interrupts // and to time the length of the press #

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.