TA0InputCapture.c

// TA0InputCapture.c
// Runs on MSP432
// Use Timer A0 in capture mode to request interrupts on the rising
// edge of P7.3 (TA0CCP0), and call a user function.
// Daniel Valvano
// July 23, 2017

/* This example accompanies the books
   "Embedded Systems: Introduction to the MSP432 Microcontroller",
       ISBN: 978-1512185676, Jonathan Valvano, copyright (c) 2017
   "Embedded Systems: Real-Time Interfacing to the MSP432 Microcontroller",
       ISBN: 978-1514676585, Jonathan Valvano, copyright (c) 2017
   "Embedded Systems: Real-Time Operating Systems for ARM Cortex-M Microcontrollers",
       ISBN: 978-1466468863, , Jonathan Valvano, copyright (c) 2017
 For more information about my classes, my research, and my books, see
 http://users.ece.utexas.edu/~valvano/

Simplified BSD License (FreeBSD License)
Copyright (c) 2017, Jonathan Valvano, All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

The views and conclusions contained in the software and documentation are
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*/

// external signal connected to P7.3 (TA0CCP0) (trigger on rising edge)

#include <stdint.h>
#include "msp.h"

void (*CaptureTask)(uint16_t time);// user function

//------------TimerCapture_Init------------
// Initialize Timer A0 in edge time mode to request interrupts on
// the rising edge of P7.3 (TA0CCP0).  The interrupt service routine
// acknowledges the interrupt and calls a user function.
// Input: task is a pointer to a user function called when edge occurs
//             parameter is 16-bit up-counting timer value when edge occurred
// Output: none
void TimerA0Capture_Init(void(*task)(uint16_t time)){
  CaptureTask = task;              // user function
  // initialize P7.3 and make it input (P7.3 TA0CCP0)
  P7->SEL0 |= 0x08;
  P7->SEL1 &= ~0x08;                 // configure P7.3 as TA0CCP0
  P7->DIR &= ~0x08;                  // make P7.3 in
  TIMER_A0->CTL &= ~0x0030;               // halt Timer A0
  // bits15-10=XXXXXX, reserved
  // bits9-8=10,       clock source to SMCLK
  // bits7-6=00,       input clock divider /1
  // bits5-4=00,       stop mode
  // bit3=X,           reserved
  // bit2=0,           set this bit to clear
  // bit1=0,           interrupt disable
  // bit0=0,           clear interrupt pending
  TIMER_A0->CTL = 0x0200;
  // bits15-14=01,     capture on rising edge
  // bits13-12=00,     capture/compare input on CCI0A
  // bit11=1,          synchronous capture source
  // bit10=X,          synchronized capture/compare input
  // bit9=X,           reserved
  // bit8=1,           capture mode
  // bits7-5=XXX,      output mode
  // bit4=1,           enable capture/compare interrupt
  // bit3=X,           read capture/compare input from here
  // bit2=X,           output this value in output mode 0
  // bit1=X,           capture overflow status
  // bit0=0,           clear capture/compare interrupt pending
  TIMER_A0->CCTL[0] = 0x4910;
  TIMER_A0->EX0 &= ~0x0007;       // configure for input clock divider /1
  NVIC->IP[2] = (NVIC->IP[2]&0xFFFFFF00)|0x00000040; // priority 2
// interrupts enabled in the main program after all devices initialized
  NVIC->ISER[0] = 0x00000100; // enable interrupt 8 in NVIC
  TIMER_A0->CTL |= 0x0024;        // reset and start Timer A0 in continuous up mode
  // bits15-10=XXXXXX, reserved
  // bits9-8=10,       clock source to SMCLK
  // bits7-6=00,       input clock divider /1
  // bits5-4=10,       continuous count up mode
  // bit3=X,           reserved
  // bit2=1,           set this bit to clear
  // bit1=0,           interrupt disable (no interrupt on rollover)
  // bit0=0,           clear interrupt pending
}

void TA0_0_IRQHandler(void){
  TIMER_A0->CCTL[0] &= ~0x0001;             // acknowledge capture/compare interrupt 0
  (*CaptureTask)(TIMER_A0->CCR[0]);         // execute user task
}