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!

Diff: TimerCapture.cpp

Revision:
0:94cfc6ceec2f
Child:
2:7c4ca945bfe1
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/TimerCapture.cpp	Thu May 21 08:04:03 2015 +0000
@@ -0,0 +1,116 @@
+#include "TimerCapture.h"
+
+bool TimerCapture::timerStarted = false;
+
+TimerCapture::TimerCapture(PinName pCapturePin) {
+    uint8_t bitcount_pinselect = 0;
+    uint8_t bitcount_capture_control = 0;
+    
+    #if DEBUG
+    printf("Entering ctor\r\n");
+    #endif
+    
+    switch (pCapturePin) {
+        case p30:
+            bitcount_pinselect = 8;
+            bitcount_capture_control = 0;
+            break;
+        case p29:
+            bitcount_pinselect = 10;
+            bitcount_capture_control = 3;
+            break;
+        default:
+            error("TimerCapture: Invalid pin specified! Pick either p29 (P0.5) or p30 (p0.4).");
+            break;
+    }
+    
+    #if DEBUG
+    printf("Bitcounts selected: %d (pinselect) %d (capture control)\r\n", bitcount_pinselect, bitcount_capture_control);
+    #endif
+    
+    uint32_t bitmask_pinselect = (0x3 << bitcount_pinselect);
+    mCapturePin = pCapturePin;
+    
+    // error out if the pin is already configured.
+    if (LPC_PINCON->PINSEL0 & bitmask_pinselect == bitmask_pinselect) {
+        error("TimerCapture: Pin is already configured!");
+    }
+    
+    #if DEBUG
+    printf("OK to configure registers\r\n");
+    #endif
+    
+    // configure the pin
+    LPC_PINCON->PINSEL0 |= bitmask_pinselect;
+    
+    #if DEBUG
+    printf("Configuring rising edge. Register is %08x\r\n", LPC_TIM2->CCR);
+    #endif
+    
+    // store on rising edge of input
+    LPC_TIM2->CCR |= (1 << bitcount_capture_control); 
+    
+    #if DEBUG
+    printf("Leaving ctor\r\n");
+    #endif
+}
+
+void TimerCapture::startTimer() {
+    if (!timerStarted) {
+        timerStarted = true;
+        
+        configureTimer();
+        
+        //start timer
+        LPC_TIM2->TCR = 1;
+    }
+}
+
+void TimerCapture::stopTimer() {
+    timerStarted = false;
+    //stop timer
+    LPC_TIM2->TCR = 0;
+}
+
+bool TimerCapture::isRunning() {
+    return timerStarted;
+}
+
+void TimerCapture::resetTimer() {
+    //reset timer
+    LPC_TIM2->TCR = 2;
+    LPC_TIM2->TCR = 0;
+    LPC_TIM2->CR0 = 0;
+    LPC_TIM2->CR1 = 0;
+}
+
+uint32_t TimerCapture::getTime() {
+    uint32_t observedTime = 0;
+    switch(mCapturePin) {
+        case p30:
+            observedTime = LPC_TIM2->CR0;
+            break;
+        case p29:
+            observedTime = LPC_TIM2->CR1;
+            break;
+        default:
+            observedTime = 0;
+            break;
+    }
+    
+    return observedTime;
+}
+
+void TimerCapture::configureTimer() {
+    // Power on Peripheral TIMER2
+    LPC_SC->PCONP |= (1 << 22);
+    
+    // Set clock source for TIMER2
+    uint8_t clockSel = 0x01;
+    LPC_SC->PCLKSEL1 |= (clockSel << 12);
+    
+    // Set prescaler counter
+    LPC_TIM2->PR = 100000; //should increment once a milisecond.
+    
+}
+       
\ No newline at end of file