Ken Todotani / mbed-src

mbed library sources

Fork of mbed-src by mbed official

targets/hal/TARGET_Freescale/TARGET_KLXX/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:
97:a69e21de83fb 
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
emilmont 10:3bc89ef62ce7 1 /* mbed Microcontroller Library
emilmont 10:3bc89ef62ce7 2 * Copyright (c) 2006-2013 ARM Limited
emilmont 10:3bc89ef62ce7 3 *
emilmont 10:3bc89ef62ce7 4 * Licensed under the Apache License, Version 2.0 (the "License");
emilmont 10:3bc89ef62ce7 5 * you may not use this file except in compliance with the License.
emilmont 10:3bc89ef62ce7 6 * You may obtain a copy of the License at
emilmont 10:3bc89ef62ce7 7 *
emilmont 10:3bc89ef62ce7 8 * http://www.apache.org/licenses/LICENSE-2.0
emilmont 10:3bc89ef62ce7 9 *
emilmont 10:3bc89ef62ce7 10 * Unless required by applicable law or agreed to in writing, software
emilmont 10:3bc89ef62ce7 11 * distributed under the License is distributed on an "AS IS" BASIS,
emilmont 10:3bc89ef62ce7 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
emilmont 10:3bc89ef62ce7 13 * See the License for the specific language governing permissions and
emilmont 10:3bc89ef62ce7 14 * limitations under the License.
emilmont 10:3bc89ef62ce7 15 */
emilmont 10:3bc89ef62ce7 16 #include <stddef.h>
emilmont 10:3bc89ef62ce7 17 #include "us_ticker_api.h"
emilmont 10:3bc89ef62ce7 18 #include "PeripheralNames.h"
mbed_official 72:248c61396e08 19 #include "clk_freqs.h"
emilmont 10:3bc89ef62ce7 20
emilmont 10:3bc89ef62ce7 21 static void pit_init(void);
emilmont 10:3bc89ef62ce7 22 static void lptmr_init(void);
emilmont 10:3bc89ef62ce7 23
emilmont 10:3bc89ef62ce7 24 static int us_ticker_inited = 0;
emilmont 10:3bc89ef62ce7 25
emilmont 10:3bc89ef62ce7 26 void us_ticker_init(void) {
emilmont 10:3bc89ef62ce7 27 if (us_ticker_inited) return;
emilmont 10:3bc89ef62ce7 28 us_ticker_inited = 1;
emilmont 10:3bc89ef62ce7 29
emilmont 10:3bc89ef62ce7 30 pit_init();
emilmont 10:3bc89ef62ce7 31 lptmr_init();
emilmont 10:3bc89ef62ce7 32 }
emilmont 10:3bc89ef62ce7 33
emilmont 10:3bc89ef62ce7 34 /******************************************************************************
emilmont 10:3bc89ef62ce7 35 * Timer for us timing.
emilmont 10:3bc89ef62ce7 36 ******************************************************************************/
emilmont 10:3bc89ef62ce7 37 static void pit_init(void) {
emilmont 10:3bc89ef62ce7 38 SIM->SCGC6 |= SIM_SCGC6_PIT_MASK; // Clock PIT
emilmont 10:3bc89ef62ce7 39 PIT->MCR = 0; // Enable PIT
emilmont 10:3bc89ef62ce7 40
emilmont 10:3bc89ef62ce7 41 // Channel 1
emilmont 10:3bc89ef62ce7 42 PIT->CHANNEL[1].LDVAL = 0xFFFFFFFF;
emilmont 10:3bc89ef62ce7 43 PIT->CHANNEL[1].TCTRL = PIT_TCTRL_CHN_MASK; // Chain to timer 0, disable Interrupts
emilmont 10:3bc89ef62ce7 44 PIT->CHANNEL[1].TCTRL |= PIT_TCTRL_TEN_MASK; // Start timer 1
emilmont 10:3bc89ef62ce7 45
emilmont 10:3bc89ef62ce7 46 // Use channel 0 as a prescaler for channel 1
mbed_official 97:a69e21de83fb 47 PIT->CHANNEL[0].LDVAL = (bus_frequency() + 500000) / 1000000 - 1;
emilmont 10:3bc89ef62ce7 48 PIT->CHANNEL[0].TCTRL = PIT_TCTRL_TEN_MASK; // Start timer 0, disable interrupts
emilmont 10:3bc89ef62ce7 49 }
emilmont 10:3bc89ef62ce7 50
emilmont 10:3bc89ef62ce7 51 uint32_t us_ticker_read() {
emilmont 10:3bc89ef62ce7 52 if (!us_ticker_inited)
emilmont 10:3bc89ef62ce7 53 us_ticker_init();
emilmont 10:3bc89ef62ce7 54
emilmont 10:3bc89ef62ce7 55 // The PIT is a countdown timer
emilmont 10:3bc89ef62ce7 56 return ~(PIT->CHANNEL[1].CVAL);
emilmont 10:3bc89ef62ce7 57 }
emilmont 10:3bc89ef62ce7 58
emilmont 10:3bc89ef62ce7 59 /******************************************************************************
emilmont 10:3bc89ef62ce7 60 * Timer Event
emilmont 10:3bc89ef62ce7 61 *
emilmont 10:3bc89ef62ce7 62 * It schedules interrupts at given (32bit)us interval of time.
emilmont 10:3bc89ef62ce7 63 * It is implemented used the 16bit Low Power Timer that remains powered in all
emilmont 10:3bc89ef62ce7 64 * power modes.
emilmont 10:3bc89ef62ce7 65 ******************************************************************************/
emilmont 10:3bc89ef62ce7 66 static void lptmr_isr(void);
emilmont 10:3bc89ef62ce7 67
emilmont 10:3bc89ef62ce7 68 static void lptmr_init(void) {
emilmont 10:3bc89ef62ce7 69 /* Clock the timer */
emilmont 10:3bc89ef62ce7 70 SIM->SCGC5 |= SIM_SCGC5_LPTMR_MASK;
emilmont 10:3bc89ef62ce7 71
emilmont 10:3bc89ef62ce7 72 /* Reset */
emilmont 10:3bc89ef62ce7 73 LPTMR0->CSR = 0;
emilmont 10:3bc89ef62ce7 74
emilmont 10:3bc89ef62ce7 75 /* Set interrupt handler */
emilmont 10:3bc89ef62ce7 76 NVIC_SetVector(LPTimer_IRQn, (uint32_t)lptmr_isr);
emilmont 10:3bc89ef62ce7 77 NVIC_EnableIRQ(LPTimer_IRQn);
emilmont 10:3bc89ef62ce7 78
emilmont 10:3bc89ef62ce7 79 /* Clock at (1)MHz -> (1)tick/us */
mbed_official 72:248c61396e08 80 /* Check if the external oscillator can be divided to 1MHz */
mbed_official 72:248c61396e08 81 uint32_t extosc = extosc_frequency();
mbed_official 72:248c61396e08 82
mbed_official 72:248c61396e08 83 if (extosc != 0) { //If external oscillator found
mbed_official 72:248c61396e08 84 if (extosc % 1000000u == 0) { //If it is a multiple if 1MHz
mbed_official 72:248c61396e08 85 extosc /= 1000000;
mbed_official 72:248c61396e08 86 if (extosc == 1) { //1MHz, set timerprescaler in bypass mode
mbed_official 72:248c61396e08 87 LPTMR0->PSR = LPTMR_PSR_PCS(3) | LPTMR_PSR_PBYP_MASK;
mbed_official 72:248c61396e08 88 return;
mbed_official 72:248c61396e08 89 } else { //See if we can divide it to 1MHz
mbed_official 72:248c61396e08 90 uint32_t divider = 0;
mbed_official 72:248c61396e08 91 extosc >>= 1;
mbed_official 72:248c61396e08 92 while (1) {
mbed_official 72:248c61396e08 93 if (extosc == 1) {
mbed_official 72:248c61396e08 94 LPTMR0->PSR = LPTMR_PSR_PCS(3) | LPTMR_PSR_PRESCALE(divider);
mbed_official 72:248c61396e08 95 return;
mbed_official 72:248c61396e08 96 }
mbed_official 72:248c61396e08 97 if (extosc % 2 != 0) //If we can't divide by two anymore
mbed_official 72:248c61396e08 98 break;
mbed_official 72:248c61396e08 99 divider++;
mbed_official 72:248c61396e08 100 extosc >>= 1;
mbed_official 72:248c61396e08 101 }
mbed_official 72:248c61396e08 102 }
mbed_official 72:248c61396e08 103 }
mbed_official 72:248c61396e08 104 }
mbed_official 74:847f030b50ee 105 //No suitable external oscillator clock -> Use fast internal oscillator (4MHz / divider)
mbed_official 72:248c61396e08 106 MCG->C1 |= MCG_C1_IRCLKEN_MASK;
mbed_official 72:248c61396e08 107 MCG->C2 |= MCG_C2_IRCS_MASK;
mbed_official 74:847f030b50ee 108 LPTMR0->PSR = LPTMR_PSR_PCS(0);
mbed_official 74:847f030b50ee 109 switch (MCG->SC & MCG_SC_FCRDIV_MASK) {
mbed_official 74:847f030b50ee 110 case MCG_SC_FCRDIV(0): //4MHz
mbed_official 74:847f030b50ee 111 LPTMR0->PSR |= LPTMR_PSR_PRESCALE(1);
mbed_official 74:847f030b50ee 112 break;
mbed_official 74:847f030b50ee 113 case MCG_SC_FCRDIV(1): //2MHz
mbed_official 74:847f030b50ee 114 LPTMR0->PSR |= LPTMR_PSR_PRESCALE(0);
mbed_official 74:847f030b50ee 115 break;
mbed_official 74:847f030b50ee 116 default: //1MHz or anything else, in which case we put it on 1MHz
mbed_official 74:847f030b50ee 117 MCG->SC &= ~MCG_SC_FCRDIV_MASK;
mbed_official 74:847f030b50ee 118 MCG->SC |= MCG_SC_FCRDIV(2);
mbed_official 74:847f030b50ee 119 LPTMR0->PSR |= LPTMR_PSR_PBYP_MASK;
mbed_official 74:847f030b50ee 120 }
mbed_official 72:248c61396e08 121
emilmont 10:3bc89ef62ce7 122 }
emilmont 10:3bc89ef62ce7 123
emilmont 10:3bc89ef62ce7 124 void us_ticker_disable_interrupt(void) {
emilmont 10:3bc89ef62ce7 125 LPTMR0->CSR &= ~LPTMR_CSR_TIE_MASK;
emilmont 10:3bc89ef62ce7 126 }
emilmont 10:3bc89ef62ce7 127
emilmont 10:3bc89ef62ce7 128 void us_ticker_clear_interrupt(void) {
emilmont 10:3bc89ef62ce7 129 // we already clear interrupt in lptmr_isr
emilmont 10:3bc89ef62ce7 130 }
emilmont 10:3bc89ef62ce7 131
emilmont 10:3bc89ef62ce7 132 static uint32_t us_ticker_int_counter = 0;
emilmont 10:3bc89ef62ce7 133 static uint16_t us_ticker_int_remainder = 0;
emilmont 10:3bc89ef62ce7 134
emilmont 10:3bc89ef62ce7 135 static void lptmr_set(unsigned short count) {
emilmont 10:3bc89ef62ce7 136 /* Reset */
emilmont 10:3bc89ef62ce7 137 LPTMR0->CSR = 0;
emilmont 10:3bc89ef62ce7 138
emilmont 10:3bc89ef62ce7 139 /* Set the compare register */
emilmont 10:3bc89ef62ce7 140 LPTMR0->CMR = count;
emilmont 10:3bc89ef62ce7 141
emilmont 10:3bc89ef62ce7 142 /* Enable interrupt */
emilmont 10:3bc89ef62ce7 143 LPTMR0->CSR |= LPTMR_CSR_TIE_MASK;
emilmont 10:3bc89ef62ce7 144
emilmont 10:3bc89ef62ce7 145 /* Start the timer */
emilmont 10:3bc89ef62ce7 146 LPTMR0->CSR |= LPTMR_CSR_TEN_MASK;
emilmont 10:3bc89ef62ce7 147 }
emilmont 10:3bc89ef62ce7 148
emilmont 10:3bc89ef62ce7 149 static void lptmr_isr(void) {
emilmont 10:3bc89ef62ce7 150 // write 1 to TCF to clear the LPT timer compare flag
emilmont 10:3bc89ef62ce7 151 LPTMR0->CSR |= LPTMR_CSR_TCF_MASK;
emilmont 10:3bc89ef62ce7 152
emilmont 10:3bc89ef62ce7 153 if (us_ticker_int_counter > 0) {
emilmont 10:3bc89ef62ce7 154 lptmr_set(0xFFFF);
emilmont 10:3bc89ef62ce7 155 us_ticker_int_counter--;
emilmont 10:3bc89ef62ce7 156
emilmont 10:3bc89ef62ce7 157 } else {
emilmont 10:3bc89ef62ce7 158 if (us_ticker_int_remainder > 0) {
emilmont 10:3bc89ef62ce7 159 lptmr_set(us_ticker_int_remainder);
emilmont 10:3bc89ef62ce7 160 us_ticker_int_remainder = 0;
emilmont 10:3bc89ef62ce7 161
emilmont 10:3bc89ef62ce7 162 } else {
emilmont 10:3bc89ef62ce7 163 // This function is going to disable the interrupts if there are
emilmont 10:3bc89ef62ce7 164 // no other events in the queue
emilmont 10:3bc89ef62ce7 165 us_ticker_irq_handler();
emilmont 10:3bc89ef62ce7 166 }
emilmont 10:3bc89ef62ce7 167 }
emilmont 10:3bc89ef62ce7 168 }
emilmont 10:3bc89ef62ce7 169
mbed_official 304:89b9c3a9a045 170 void us_ticker_set_interrupt(timestamp_t timestamp) {
mbed_official 304:89b9c3a9a045 171 int delta = (int)((uint32_t)timestamp - us_ticker_read());
emilmont 10:3bc89ef62ce7 172 if (delta <= 0) {
emilmont 10:3bc89ef62ce7 173 // This event was in the past:
emilmont 10:3bc89ef62ce7 174 us_ticker_irq_handler();
emilmont 10:3bc89ef62ce7 175 return;
emilmont 10:3bc89ef62ce7 176 }
emilmont 10:3bc89ef62ce7 177
emilmont 10:3bc89ef62ce7 178 us_ticker_int_counter = (uint32_t)(delta >> 16);
emilmont 10:3bc89ef62ce7 179 us_ticker_int_remainder = (uint16_t)(0xFFFF & delta);
emilmont 10:3bc89ef62ce7 180 if (us_ticker_int_counter > 0) {
emilmont 10:3bc89ef62ce7 181 lptmr_set(0xFFFF);
emilmont 10:3bc89ef62ce7 182 us_ticker_int_counter--;
emilmont 10:3bc89ef62ce7 183 } else {
emilmont 10:3bc89ef62ce7 184 lptmr_set(us_ticker_int_remainder);
emilmont 10:3bc89ef62ce7 185 us_ticker_int_remainder = 0;
emilmont 10:3bc89ef62ce7 186 }
emilmont 10:3bc89ef62ce7 187 }