Gary Richardson / Mbed 2 deprecated Counter

Use of two timers to implement a counter of an external signal

Dependencies:   mbed

Timer2.cpp@0:e619b6823668, 2014-01-28 (annotated)

Committer:
garyr
Date:
Tue Jan 28 17:01:19 2014 +0000
Revision:
0:e619b6823668
First working version

Who changed what in which revision?

UserRevisionLine numberNew contents of line
garyr 0:e619b6823668 1
garyr 0:e619b6823668 2 /*
garyr 0:e619b6823668 3 This counter establishes the measurent interval.
garyr 0:e619b6823668 4 MAT2.0 (P8) is set when the interval has elapsed.
garyr 0:e619b6823668 5
garyr 0:e619b6823668 6 This code generates timed intervals T = <prescale> * 100 ms.
garyr 0:e619b6823668 7 mbed pin 8 goes high at the beginning of the interval and returns to zero at the end.
garyr 0:e619b6823668 8 The interrupt occurs at the end of the interval.
garyr 0:e619b6823668 9 */
garyr 0:e619b6823668 10 #include "TARGET_LPC1768/LPC17xx.h"
garyr 0:e619b6823668 11 #include "mbed.h"
garyr 0:e619b6823668 12 #include "Timer2.h"
garyr 0:e619b6823668 13
garyr 0:e619b6823668 14 funcptr timer2ISR;
garyr 0:e619b6823668 15
garyr 0:e619b6823668 16 void Timer2_IRQHandler(void)
garyr 0:e619b6823668 17 {
garyr 0:e619b6823668 18 if (LPC_TIM2->IR & 1) // MR0 interrupt
garyr 0:e619b6823668 19 {
garyr 0:e619b6823668 20 LPC_TIM2->IR = 1; // clear the interrupt
garyr 0:e619b6823668 21 if (timer2ISR)
garyr 0:e619b6823668 22 timer2ISR();
garyr 0:e619b6823668 23 }
garyr 0:e619b6823668 24 }
garyr 0:e619b6823668 25
garyr 0:e619b6823668 26 void Timer2_init(funcptr callback)
garyr 0:e619b6823668 27 {
garyr 0:e619b6823668 28 timer2ISR = callback;
garyr 0:e619b6823668 29 LPC_SC->PCONP |= (1<<22); // Power on the Timer2
garyr 0:e619b6823668 30 LPC_SC->PCLKSEL1 &= ~(3<<12);
garyr 0:e619b6823668 31 LPC_SC->PCLKSEL1 |= (1<<12); // Select CCLK for Timer2
garyr 0:e619b6823668 32 LPC_PINCON->PINSEL0 &=~(3<<12);
garyr 0:e619b6823668 33 LPC_PINCON->PINSEL0 |= (3<<12); // Connect MAT2.0 to mbed P8
garyr 0:e619b6823668 34 LPC_PINCON->PINMODE0 &=~(3<<12);
garyr 0:e619b6823668 35 LPC_PINCON->PINMODE0 |= (2<<12); // no pull-p or pull-down
garyr 0:e619b6823668 36 if (callback)
garyr 0:e619b6823668 37 {
garyr 0:e619b6823668 38 NVIC_SetPriority(TIMER2_IRQn, 10);
garyr 0:e619b6823668 39 NVIC_SetVector(TIMER2_IRQn, (uint32_t)&Timer2_IRQHandler);
garyr 0:e619b6823668 40 NVIC_EnableIRQ(TIMER2_IRQn);
garyr 0:e619b6823668 41 }
garyr 0:e619b6823668 42 }
garyr 0:e619b6823668 43 void Timer2_start(int prescale)
garyr 0:e619b6823668 44 {
garyr 0:e619b6823668 45 LPC_TIM2->TCR = 2; // Reset the timer and prescale counters on next PCLK
garyr 0:e619b6823668 46 LPC_TIM2->MR0 = CLOCK/10; // Set the Timer2 match register for 100 ms resolution
garyr 0:e619b6823668 47 LPC_TIM2->CTCR = 0; // Timer2 is incremented when the prescale register == 0
garyr 0:e619b6823668 48 LPC_TIM2->PR = prescale; // Update prescale register
garyr 0:e619b6823668 49 LPC_TIM2->MCR = 3; // Interrupt on MR0 and reset
garyr 0:e619b6823668 50 LPC_TIM2->EMR = (3<<4)|1; // Toggle MAT2.0 when match occurs.
garyr 0:e619b6823668 51 LPC_TIM2->TCR = 1; // Enable Timer2
garyr 0:e619b6823668 52 LPC_TIM3->TCR = 1; // Enable Timer3
garyr 0:e619b6823668 53 }