Andrew Boyson / clock

Important changes to repositories hosted on mbed.com

Mbed hosted mercurial repositories are deprecated and are due to be permanently deleted in July 2026.

To keep a copy of this software download the repository Zip archive or clone locally using Mercurial.

It is also possible to export all your personal repositories from the account settings page.

Dependents:   oldheating gps motorhome heating

timer.c@31:f6ff7fdb9c67, 2018-11-29 (annotated)

Committer:
andrewboyson
Date:
Thu Nov 29 16:51:19 2018 +0000
Revision:
31:f6ff7fdb9c67
Parent:
30:212ca42b8779
Child:
33:b9e3c06e7dab
Changed time.c to tm.c

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 24:6c9833e2a049 1 #include <stdint.h>
andrewboyson 26:0421132e6eaf 2 #include <stdbool.h>
andrewboyson 24:6c9833e2a049 3
andrewboyson 25:81014a201736 4 #include "timer.h"
andrewboyson 24:6c9833e2a049 5
andrewboyson 30:212ca42b8779 6 #define TCR (*((volatile unsigned *) 0x40004004))
andrewboyson 30:212ca42b8779 7 #define TC (*((volatile unsigned *) 0x40004008))
andrewboyson 30:212ca42b8779 8 #define PR (*((volatile unsigned *) 0x4000400C))
andrewboyson 30:212ca42b8779 9 #define MCR (*((volatile unsigned *) 0x40004014))
andrewboyson 30:212ca42b8779 10 #define CTCR (*((volatile unsigned *) 0x40004070))
andrewboyson 30:212ca42b8779 11
andrewboyson 26:0421132e6eaf 12 uint32_t TimerNowCount()
andrewboyson 26:0421132e6eaf 13 {
andrewboyson 30:212ca42b8779 14 return TC;
andrewboyson 24:6c9833e2a049 15 }
andrewboyson 26:0421132e6eaf 16 uint32_t TimerIntervalCount(uint32_t* pLastCount)
andrewboyson 24:6c9833e2a049 17 {
andrewboyson 30:212ca42b8779 18 uint32_t thisCount = TC;
andrewboyson 24:6c9833e2a049 19 uint32_t period = thisCount - *pLastCount;
andrewboyson 24:6c9833e2a049 20 *pLastCount = thisCount;
andrewboyson 24:6c9833e2a049 21 return period;
andrewboyson 24:6c9833e2a049 22 }
andrewboyson 24:6c9833e2a049 23 uint32_t TimerSinceCount(uint32_t startCount)
andrewboyson 24:6c9833e2a049 24 {
andrewboyson 30:212ca42b8779 25 return TC - startCount;
andrewboyson 24:6c9833e2a049 26 }
andrewboyson 24:6c9833e2a049 27 uint32_t TimerSinceMs(uint32_t startCount)
andrewboyson 24:6c9833e2a049 28 {
andrewboyson 30:212ca42b8779 29 uint32_t count = TC - startCount;
andrewboyson 25:81014a201736 30 return count / TIMER_COUNT_PER_MS;
andrewboyson 24:6c9833e2a049 31 }
andrewboyson 26:0421132e6eaf 32
andrewboyson 26:0421132e6eaf 33 static uint32_t secondsBaseCount = 0;
andrewboyson 26:0421132e6eaf 34
andrewboyson 26:0421132e6eaf 35 uint32_t TimerCountSinceLastSecond()
andrewboyson 26:0421132e6eaf 36 {
andrewboyson 30:212ca42b8779 37 return TC - secondsBaseCount;
andrewboyson 26:0421132e6eaf 38 }
andrewboyson 26:0421132e6eaf 39 int32_t TimerMultiplyFractionalPart(int32_t value, uint32_t timerCountSinceLastSecond)
andrewboyson 26:0421132e6eaf 40 {
andrewboyson 26:0421132e6eaf 41 int64_t fraction;
andrewboyson 26:0421132e6eaf 42
andrewboyson 26:0421132e6eaf 43 fraction = timerCountSinceLastSecond;
andrewboyson 26:0421132e6eaf 44 fraction <<= 32;
andrewboyson 26:0421132e6eaf 45 fraction /= TIMER_COUNT_PER_SECOND;
andrewboyson 26:0421132e6eaf 46
andrewboyson 26:0421132e6eaf 47 return (value * fraction) >> 32;
andrewboyson 26:0421132e6eaf 48 }
andrewboyson 26:0421132e6eaf 49
andrewboyson 31:f6ff7fdb9c67 50 bool TimerHadSecond = false;
andrewboyson 31:f6ff7fdb9c67 51
andrewboyson 31:f6ff7fdb9c67 52 //Counts from zero to 2^32 and wraps around after:
andrewboyson 31:f6ff7fdb9c67 53 // 13.7 years if 10 per second - scan time must be less than 100mS
andrewboyson 31:f6ff7fdb9c67 54 // 1.37 years if 100 per second - scan time must be less than 10mS
andrewboyson 31:f6ff7fdb9c67 55 uint32_t TimerTicks = 0;
andrewboyson 26:0421132e6eaf 56
andrewboyson 26:0421132e6eaf 57 void TimerMain()
andrewboyson 26:0421132e6eaf 58 {
andrewboyson 31:f6ff7fdb9c67 59 TimerHadSecond = TimerCountSinceLastSecond() > TIMER_COUNT_PER_SECOND;
andrewboyson 31:f6ff7fdb9c67 60 if (TimerHadSecond) secondsBaseCount += TIMER_COUNT_PER_SECOND;
andrewboyson 31:f6ff7fdb9c67 61
andrewboyson 31:f6ff7fdb9c67 62 static uint32_t tickBaseCount = 0;
andrewboyson 26:0421132e6eaf 63
andrewboyson 31:f6ff7fdb9c67 64 if (TC - tickBaseCount > TIMER_COUNT_PER_SECOND / TIMER_TICKS_PER_SECOND)
andrewboyson 31:f6ff7fdb9c67 65 {
andrewboyson 31:f6ff7fdb9c67 66 TimerTicks++;
andrewboyson 31:f6ff7fdb9c67 67 tickBaseCount += TIMER_COUNT_PER_SECOND / TIMER_TICKS_PER_SECOND;
andrewboyson 31:f6ff7fdb9c67 68 }
andrewboyson 26:0421132e6eaf 69 }
andrewboyson 26:0421132e6eaf 70 void TimerInit()
andrewboyson 26:0421132e6eaf 71 {
andrewboyson 30:212ca42b8779 72 TCR = 2; // 21.6.2 Timer Control Register - Reset TC and PC.
andrewboyson 30:212ca42b8779 73 CTCR = 0; // 21.6.3 Count Control Register - Timer mode
andrewboyson 30:212ca42b8779 74 PR = 0; // 21.6.5 Prescale register - Don't prescale 96MHz clock (divide by PR+1).
andrewboyson 30:212ca42b8779 75 MCR = 0; // 21.6.8 Match Control Register - no interrupt or reset
andrewboyson 30:212ca42b8779 76 TCR = 1; // 21.6.2 Timer Control Register - Enable TC and PC
andrewboyson 26:0421132e6eaf 77 }