Ken Todotani / mbed-src

mbed library sources

Fork of mbed-src by mbed official

targets/hal/TARGET_Freescale/TARGET_K20D50M/us_ticker.c@304:89b9c3a9a045, 2014-08-29 (annotated)

Committer:
mbed_official
Date:
Fri Aug 29 17:15:07 2014 +0100
Revision:
304:89b9c3a9a045
Parent:
255:20b371a9491b 
Synchronized with git revision 734f365d7da26ef199751f4b0d91611479b495ea



Full URL: https://github.com/mbedmicro/mbed/commit/734f365d7da26ef199751f4b0d91611479b495ea/



1. timestamp_t as an abstraction for time values managed by

   Ticker. Using uint64_t for timestamp_t allows a wraparound-free

   Ticker. This change forces us to update the definitions of usTicker

   for all platforms; but the changes beyond nRF51822 aren't major.



2. reduce power consumption on the nRF51822 by removing the need for

   the high-frequency processor timer; and reimplementing it using the

   RTC.



I've also replaced high-frequency clock with low-frequency external

clock during system startup of the nRF51822. This brings a major win

in power consumption.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mbed_official 68:41613245dfd7 1 /* mbed Microcontroller Library
mbed_official 68:41613245dfd7 2 * Copyright (c) 2006-2013 ARM Limited
mbed_official 68:41613245dfd7 3 *
mbed_official 68:41613245dfd7 4 * Licensed under the Apache License, Version 2.0 (the "License");
mbed_official 68:41613245dfd7 5 * you may not use this file except in compliance with the License.
mbed_official 68:41613245dfd7 6 * You may obtain a copy of the License at
mbed_official 68:41613245dfd7 7 *
mbed_official 68:41613245dfd7 8 * http://www.apache.org/licenses/LICENSE-2.0
mbed_official 68:41613245dfd7 9 *
mbed_official 68:41613245dfd7 10 * Unless required by applicable law or agreed to in writing, software
mbed_official 68:41613245dfd7 11 * distributed under the License is distributed on an "AS IS" BASIS,
mbed_official 68:41613245dfd7 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
mbed_official 68:41613245dfd7 13 * See the License for the specific language governing permissions and
mbed_official 68:41613245dfd7 14 * limitations under the License.
mbed_official 68:41613245dfd7 15 */
mbed_official 68:41613245dfd7 16 #include <stddef.h>
mbed_official 68:41613245dfd7 17 #include "us_ticker_api.h"
mbed_official 68:41613245dfd7 18 #include "PeripheralNames.h"
mbed_official 73:299c67215126 19 #include "clk_freqs.h"
mbed_official 68:41613245dfd7 20
mbed_official 161:09d8213f0000 21 #define PIT_TIMER PIT->CHANNEL[0]
mbed_official 161:09d8213f0000 22 #define PIT_TIMER_IRQ PIT0_IRQn
mbed_official 161:09d8213f0000 23 #define PIT_TICKER PIT->CHANNEL[1]
mbed_official 161:09d8213f0000 24 #define PIT_TICKER_IRQ PIT1_IRQn
mbed_official 161:09d8213f0000 25
mbed_official 161:09d8213f0000 26 static void timer_init(void);
mbed_official 161:09d8213f0000 27 static void ticker_init(void);
mbed_official 68:41613245dfd7 28
mbed_official 73:299c67215126 29
mbed_official 68:41613245dfd7 30 static int us_ticker_inited = 0;
mbed_official 161:09d8213f0000 31 static uint32_t clk_mhz;
mbed_official 68:41613245dfd7 32
mbed_official 68:41613245dfd7 33 void us_ticker_init(void) {
mbed_official 68:41613245dfd7 34 if (us_ticker_inited)
mbed_official 68:41613245dfd7 35 return;
mbed_official 68:41613245dfd7 36 us_ticker_inited = 1;
mbed_official 161:09d8213f0000 37
mbed_official 161:09d8213f0000 38 SIM->SCGC6 |= SIM_SCGC6_PIT_MASK; // Clock PIT
mbed_official 161:09d8213f0000 39 PIT->MCR = 0; // Enable PIT
mbed_official 161:09d8213f0000 40
mbed_official 161:09d8213f0000 41 clk_mhz = bus_frequency() / 1000000;
mbed_official 68:41613245dfd7 42
mbed_official 161:09d8213f0000 43 timer_init();
mbed_official 161:09d8213f0000 44 ticker_init();
mbed_official 68:41613245dfd7 45 }
mbed_official 68:41613245dfd7 46
mbed_official 68:41613245dfd7 47 /******************************************************************************
mbed_official 68:41613245dfd7 48 * Timer for us timing.
mbed_official 161:09d8213f0000 49 *
mbed_official 161:09d8213f0000 50 * The K20D5M does not have a prescaler on its PIT timer nor the option
mbed_official 161:09d8213f0000 51 * to chain timers, which is why a software timer is required to get 32-bit
mbed_official 161:09d8213f0000 52 * word length.
mbed_official 68:41613245dfd7 53 ******************************************************************************/
mbed_official 161:09d8213f0000 54 static volatile uint32_t msb_counter = 0;
mbed_official 161:09d8213f0000 55 static uint32_t timer_ldval = 0;
mbed_official 73:299c67215126 56
mbed_official 161:09d8213f0000 57 static void timer_isr(void) {
mbed_official 161:09d8213f0000 58 msb_counter++;
mbed_official 161:09d8213f0000 59 PIT_TIMER.TFLG = 1;
mbed_official 161:09d8213f0000 60 }
mbed_official 68:41613245dfd7 61
mbed_official 161:09d8213f0000 62 static void timer_init(void) {
mbed_official 161:09d8213f0000 63 //CLZ counts the leading zeros, returning number of bits not used by clk_mhz
mbed_official 161:09d8213f0000 64 timer_ldval = clk_mhz << __CLZ(clk_mhz);
mbed_official 161:09d8213f0000 65
mbed_official 161:09d8213f0000 66 PIT_TIMER.LDVAL = timer_ldval; // 1us
mbed_official 161:09d8213f0000 67 PIT_TIMER.TCTRL |= PIT_TCTRL_TIE_MASK;
mbed_official 161:09d8213f0000 68 PIT_TIMER.TCTRL |= PIT_TCTRL_TEN_MASK; // Start timer 0
mbed_official 161:09d8213f0000 69
mbed_official 161:09d8213f0000 70 NVIC_SetVector(PIT_TIMER_IRQ, (uint32_t)timer_isr);
mbed_official 161:09d8213f0000 71 NVIC_EnableIRQ(PIT_TIMER_IRQ);
mbed_official 68:41613245dfd7 72 }
mbed_official 68:41613245dfd7 73
mbed_official 68:41613245dfd7 74 uint32_t us_ticker_read() {
mbed_official 68:41613245dfd7 75 if (!us_ticker_inited)
mbed_official 68:41613245dfd7 76 us_ticker_init();
mbed_official 161:09d8213f0000 77
mbed_official 161:09d8213f0000 78 uint32_t retval;
mbed_official 161:09d8213f0000 79 __disable_irq();
mbed_official 161:09d8213f0000 80 retval = (timer_ldval - PIT_TIMER.CVAL) / clk_mhz; //Hardware bits
mbed_official 161:09d8213f0000 81 retval |= msb_counter << __CLZ(clk_mhz); //Software bits
mbed_official 161:09d8213f0000 82
mbed_official 161:09d8213f0000 83 if (PIT_TIMER.TFLG == 1) { //If overflow bit is set, force it to be handled
mbed_official 161:09d8213f0000 84 timer_isr(); //Handle IRQ, read again to make sure software/hardware bits are synced
mbed_official 161:09d8213f0000 85 NVIC_ClearPendingIRQ(PIT_TIMER_IRQ);
mbed_official 161:09d8213f0000 86 return us_ticker_read();
mbed_official 161:09d8213f0000 87 }
mbed_official 68:41613245dfd7 88
mbed_official 161:09d8213f0000 89 __enable_irq();
mbed_official 161:09d8213f0000 90 return retval;
mbed_official 68:41613245dfd7 91 }
mbed_official 68:41613245dfd7 92
mbed_official 68:41613245dfd7 93 /******************************************************************************
mbed_official 68:41613245dfd7 94 * Timer Event
mbed_official 68:41613245dfd7 95 *
mbed_official 68:41613245dfd7 96 * It schedules interrupts at given (32bit)us interval of time.
mbed_official 161:09d8213f0000 97 * It is implemented using PIT channel 1, since no prescaler is available,
mbed_official 161:09d8213f0000 98 * some bits are implemented in software.
mbed_official 68:41613245dfd7 99 ******************************************************************************/
mbed_official 161:09d8213f0000 100 static void ticker_isr(void);
mbed_official 73:299c67215126 101
mbed_official 161:09d8213f0000 102 static void ticker_init(void) {
mbed_official 161:09d8213f0000 103 /* Set interrupt handler */
mbed_official 161:09d8213f0000 104 NVIC_SetVector(PIT_TICKER_IRQ, (uint32_t)ticker_isr);
mbed_official 161:09d8213f0000 105 NVIC_EnableIRQ(PIT_TICKER_IRQ);
mbed_official 68:41613245dfd7 106 }
mbed_official 68:41613245dfd7 107
mbed_official 68:41613245dfd7 108 void us_ticker_disable_interrupt(void) {
mbed_official 161:09d8213f0000 109 PIT_TICKER.TCTRL &= ~PIT_TCTRL_TIE_MASK;
mbed_official 68:41613245dfd7 110 }
mbed_official 68:41613245dfd7 111
mbed_official 68:41613245dfd7 112 void us_ticker_clear_interrupt(void) {
mbed_official 68:41613245dfd7 113 // we already clear interrupt in lptmr_isr
mbed_official 68:41613245dfd7 114 }
mbed_official 68:41613245dfd7 115
mbed_official 68:41613245dfd7 116 static uint32_t us_ticker_int_counter = 0;
mbed_official 68:41613245dfd7 117
mbed_official 161:09d8213f0000 118 inline static void ticker_set(uint32_t count) {
mbed_official 161:09d8213f0000 119 PIT_TICKER.TCTRL = 0;
mbed_official 161:09d8213f0000 120 PIT_TICKER.LDVAL = count;
mbed_official 161:09d8213f0000 121 PIT_TICKER.TCTRL = PIT_TCTRL_TIE_MASK | PIT_TCTRL_TEN_MASK;
mbed_official 68:41613245dfd7 122 }
mbed_official 68:41613245dfd7 123
mbed_official 161:09d8213f0000 124 static void ticker_isr(void) {
mbed_official 161:09d8213f0000 125 // Clear IRQ flag
mbed_official 161:09d8213f0000 126 PIT_TICKER.TFLG = 1;
mbed_official 68:41613245dfd7 127
mbed_official 68:41613245dfd7 128 if (us_ticker_int_counter > 0) {
mbed_official 161:09d8213f0000 129 ticker_set(0xFFFFFFFF);
mbed_official 68:41613245dfd7 130 us_ticker_int_counter--;
mbed_official 68:41613245dfd7 131 } else {
mbed_official 161:09d8213f0000 132 // This function is going to disable the interrupts if there are
mbed_official 161:09d8213f0000 133 // no other events in the queue
mbed_official 161:09d8213f0000 134 us_ticker_irq_handler();
mbed_official 68:41613245dfd7 135 }
mbed_official 68:41613245dfd7 136 }
mbed_official 68:41613245dfd7 137
mbed_official 304:89b9c3a9a045 138 void us_ticker_set_interrupt(timestamp_t timestamp) {
mbed_official 304:89b9c3a9a045 139 int delta = (int)((uint32_t)timestamp - us_ticker_read());
mbed_official 68:41613245dfd7 140 if (delta <= 0) {
mbed_official 68:41613245dfd7 141 // This event was in the past:
mbed_official 68:41613245dfd7 142 us_ticker_irq_handler();
mbed_official 68:41613245dfd7 143 return;
mbed_official 68:41613245dfd7 144 }
mbed_official 68:41613245dfd7 145
mbed_official 161:09d8213f0000 146 //Calculate how much falls outside the 32-bit after multiplying with clk_mhz
mbed_official 161:09d8213f0000 147 //We shift twice 16-bit to keep everything within the 32-bit variable
mbed_official 161:09d8213f0000 148 us_ticker_int_counter = (uint32_t)(delta >> 16);
mbed_official 161:09d8213f0000 149 us_ticker_int_counter *= clk_mhz;
mbed_official 161:09d8213f0000 150 us_ticker_int_counter >>= 16;
mbed_official 161:09d8213f0000 151
mbed_official 161:09d8213f0000 152 uint32_t us_ticker_int_remainder = (uint32_t)delta * clk_mhz;
mbed_official 161:09d8213f0000 153 if (us_ticker_int_remainder == 0) {
mbed_official 161:09d8213f0000 154 ticker_set(0xFFFFFFFF);
mbed_official 68:41613245dfd7 155 us_ticker_int_counter--;
mbed_official 68:41613245dfd7 156 } else {
mbed_official 161:09d8213f0000 157 ticker_set(us_ticker_int_remainder);
mbed_official 68:41613245dfd7 158 }
mbed_official 68:41613245dfd7 159 }