Vishal Kotcherlakota / TimerCapture

Library to simplify using capture pins on hardware.

Dependents:   bluesync

When I first started experimenting with the notion of capture pins, I had no idea where to begin. Rather than write to registers in every single program, I decided to create a class that'd handle that heavy lifting for me!

Import library
TimerCapture - TimerCapture Class Reference

Public Member Functions

TimerCapture (PinName pCapturePin)
Configures registers to use the given pin as a capture pin.
uint32_t getTime ()
Get the time captured by the capture pin's register.

Static Public Member Functions

static void startTimer ()
Starts the TIMER2 timer, and configures it if it's not already configured.
static bool isRunning ()
Checks if the TIMER2 timer is running.
static void stopTimer ()
Stops the TIMER2 timer.
static void resetTimer ()
Resets the TIMER2 timer.

This code uses TIMER2 on the LPC1768. I have no idea if it will work on other hardware, but I hope it helps someone else!

TimerCapture.cpp@0:94cfc6ceec2f, 2015-05-21 (annotated)

Committer:
dishbreak
Date:
Thu May 21 08:04:03 2015 +0000
Revision:
0:94cfc6ceec2f
Child:
2:7c4ca945bfe1
Initial commit of TimerCapture code.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
dishbreak 0:94cfc6ceec2f 1 #include "TimerCapture.h"
dishbreak 0:94cfc6ceec2f 2
dishbreak 0:94cfc6ceec2f 3 bool TimerCapture::timerStarted = false;
dishbreak 0:94cfc6ceec2f 4
dishbreak 0:94cfc6ceec2f 5 TimerCapture::TimerCapture(PinName pCapturePin) {
dishbreak 0:94cfc6ceec2f 6 uint8_t bitcount_pinselect = 0;
dishbreak 0:94cfc6ceec2f 7 uint8_t bitcount_capture_control = 0;
dishbreak 0:94cfc6ceec2f 8
dishbreak 0:94cfc6ceec2f 9 #if DEBUG
dishbreak 0:94cfc6ceec2f 10 printf("Entering ctor\r\n");
dishbreak 0:94cfc6ceec2f 11 #endif
dishbreak 0:94cfc6ceec2f 12
dishbreak 0:94cfc6ceec2f 13 switch (pCapturePin) {
dishbreak 0:94cfc6ceec2f 14 case p30:
dishbreak 0:94cfc6ceec2f 15 bitcount_pinselect = 8;
dishbreak 0:94cfc6ceec2f 16 bitcount_capture_control = 0;
dishbreak 0:94cfc6ceec2f 17 break;
dishbreak 0:94cfc6ceec2f 18 case p29:
dishbreak 0:94cfc6ceec2f 19 bitcount_pinselect = 10;
dishbreak 0:94cfc6ceec2f 20 bitcount_capture_control = 3;
dishbreak 0:94cfc6ceec2f 21 break;
dishbreak 0:94cfc6ceec2f 22 default:
dishbreak 0:94cfc6ceec2f 23 error("TimerCapture: Invalid pin specified! Pick either p29 (P0.5) or p30 (p0.4).");
dishbreak 0:94cfc6ceec2f 24 break;
dishbreak 0:94cfc6ceec2f 25 }
dishbreak 0:94cfc6ceec2f 26
dishbreak 0:94cfc6ceec2f 27 #if DEBUG
dishbreak 0:94cfc6ceec2f 28 printf("Bitcounts selected: %d (pinselect) %d (capture control)\r\n", bitcount_pinselect, bitcount_capture_control);
dishbreak 0:94cfc6ceec2f 29 #endif
dishbreak 0:94cfc6ceec2f 30
dishbreak 0:94cfc6ceec2f 31 uint32_t bitmask_pinselect = (0x3 << bitcount_pinselect);
dishbreak 0:94cfc6ceec2f 32 mCapturePin = pCapturePin;
dishbreak 0:94cfc6ceec2f 33
dishbreak 0:94cfc6ceec2f 34 // error out if the pin is already configured.
dishbreak 0:94cfc6ceec2f 35 if (LPC_PINCON->PINSEL0 & bitmask_pinselect == bitmask_pinselect) {
dishbreak 0:94cfc6ceec2f 36 error("TimerCapture: Pin is already configured!");
dishbreak 0:94cfc6ceec2f 37 }
dishbreak 0:94cfc6ceec2f 38
dishbreak 0:94cfc6ceec2f 39 #if DEBUG
dishbreak 0:94cfc6ceec2f 40 printf("OK to configure registers\r\n");
dishbreak 0:94cfc6ceec2f 41 #endif
dishbreak 0:94cfc6ceec2f 42
dishbreak 0:94cfc6ceec2f 43 // configure the pin
dishbreak 0:94cfc6ceec2f 44 LPC_PINCON->PINSEL0 |= bitmask_pinselect;
dishbreak 0:94cfc6ceec2f 45
dishbreak 0:94cfc6ceec2f 46 #if DEBUG
dishbreak 0:94cfc6ceec2f 47 printf("Configuring rising edge. Register is %08x\r\n", LPC_TIM2->CCR);
dishbreak 0:94cfc6ceec2f 48 #endif
dishbreak 0:94cfc6ceec2f 49
dishbreak 0:94cfc6ceec2f 50 // store on rising edge of input
dishbreak 0:94cfc6ceec2f 51 LPC_TIM2->CCR |= (1 << bitcount_capture_control);
dishbreak 0:94cfc6ceec2f 52
dishbreak 0:94cfc6ceec2f 53 #if DEBUG
dishbreak 0:94cfc6ceec2f 54 printf("Leaving ctor\r\n");
dishbreak 0:94cfc6ceec2f 55 #endif
dishbreak 0:94cfc6ceec2f 56 }
dishbreak 0:94cfc6ceec2f 57
dishbreak 0:94cfc6ceec2f 58 void TimerCapture::startTimer() {
dishbreak 0:94cfc6ceec2f 59 if (!timerStarted) {
dishbreak 0:94cfc6ceec2f 60 timerStarted = true;
dishbreak 0:94cfc6ceec2f 61
dishbreak 0:94cfc6ceec2f 62 configureTimer();
dishbreak 0:94cfc6ceec2f 63
dishbreak 0:94cfc6ceec2f 64 //start timer
dishbreak 0:94cfc6ceec2f 65 LPC_TIM2->TCR = 1;
dishbreak 0:94cfc6ceec2f 66 }
dishbreak 0:94cfc6ceec2f 67 }
dishbreak 0:94cfc6ceec2f 68
dishbreak 0:94cfc6ceec2f 69 void TimerCapture::stopTimer() {
dishbreak 0:94cfc6ceec2f 70 timerStarted = false;
dishbreak 0:94cfc6ceec2f 71 //stop timer
dishbreak 0:94cfc6ceec2f 72 LPC_TIM2->TCR = 0;
dishbreak 0:94cfc6ceec2f 73 }
dishbreak 0:94cfc6ceec2f 74
dishbreak 0:94cfc6ceec2f 75 bool TimerCapture::isRunning() {
dishbreak 0:94cfc6ceec2f 76 return timerStarted;
dishbreak 0:94cfc6ceec2f 77 }
dishbreak 0:94cfc6ceec2f 78
dishbreak 0:94cfc6ceec2f 79 void TimerCapture::resetTimer() {
dishbreak 0:94cfc6ceec2f 80 //reset timer
dishbreak 0:94cfc6ceec2f 81 LPC_TIM2->TCR = 2;
dishbreak 0:94cfc6ceec2f 82 LPC_TIM2->TCR = 0;
dishbreak 0:94cfc6ceec2f 83 LPC_TIM2->CR0 = 0;
dishbreak 0:94cfc6ceec2f 84 LPC_TIM2->CR1 = 0;
dishbreak 0:94cfc6ceec2f 85 }
dishbreak 0:94cfc6ceec2f 86
dishbreak 0:94cfc6ceec2f 87 uint32_t TimerCapture::getTime() {
dishbreak 0:94cfc6ceec2f 88 uint32_t observedTime = 0;
dishbreak 0:94cfc6ceec2f 89 switch(mCapturePin) {
dishbreak 0:94cfc6ceec2f 90 case p30:
dishbreak 0:94cfc6ceec2f 91 observedTime = LPC_TIM2->CR0;
dishbreak 0:94cfc6ceec2f 92 break;
dishbreak 0:94cfc6ceec2f 93 case p29:
dishbreak 0:94cfc6ceec2f 94 observedTime = LPC_TIM2->CR1;
dishbreak 0:94cfc6ceec2f 95 break;
dishbreak 0:94cfc6ceec2f 96 default:
dishbreak 0:94cfc6ceec2f 97 observedTime = 0;
dishbreak 0:94cfc6ceec2f 98 break;
dishbreak 0:94cfc6ceec2f 99 }
dishbreak 0:94cfc6ceec2f 100
dishbreak 0:94cfc6ceec2f 101 return observedTime;
dishbreak 0:94cfc6ceec2f 102 }
dishbreak 0:94cfc6ceec2f 103
dishbreak 0:94cfc6ceec2f 104 void TimerCapture::configureTimer() {
dishbreak 0:94cfc6ceec2f 105 // Power on Peripheral TIMER2
dishbreak 0:94cfc6ceec2f 106 LPC_SC->PCONP |= (1 << 22);
dishbreak 0:94cfc6ceec2f 107
dishbreak 0:94cfc6ceec2f 108 // Set clock source for TIMER2
dishbreak 0:94cfc6ceec2f 109 uint8_t clockSel = 0x01;
dishbreak 0:94cfc6ceec2f 110 LPC_SC->PCLKSEL1 |= (clockSel << 12);
dishbreak 0:94cfc6ceec2f 111
dishbreak 0:94cfc6ceec2f 112 // Set prescaler counter
dishbreak 0:94cfc6ceec2f 113 LPC_TIM2->PR = 100000; //should increment once a milisecond.
dishbreak 0:94cfc6ceec2f 114
dishbreak 0:94cfc6ceec2f 115 }
dishbreak 0:94cfc6ceec2f 116