zain aftab / mbed-src2

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targets/hal/TARGET_NORDIC/TARGET_MCU_NRF51822/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:
300:55638feb26a4
Child:
361:56c2a6244bba
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 85:e1a8e879a6a9 1 /* mbed Microcontroller Library
mbed_official 104:a6a92e2e5a92 2 * Copyright (c) 2013 Nordic Semiconductor
mbed_official 85:e1a8e879a6a9 3 *
mbed_official 85:e1a8e879a6a9 4 * Licensed under the Apache License, Version 2.0 (the "License");
mbed_official 85:e1a8e879a6a9 5 * you may not use this file except in compliance with the License.
mbed_official 85:e1a8e879a6a9 6 * You may obtain a copy of the License at
mbed_official 85:e1a8e879a6a9 7 *
mbed_official 85:e1a8e879a6a9 8 * http://www.apache.org/licenses/LICENSE-2.0
mbed_official 85:e1a8e879a6a9 9 *
mbed_official 85:e1a8e879a6a9 10 * Unless required by applicable law or agreed to in writing, software
mbed_official 85:e1a8e879a6a9 11 * distributed under the License is distributed on an "AS IS" BASIS,
mbed_official 85:e1a8e879a6a9 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
mbed_official 85:e1a8e879a6a9 13 * See the License for the specific language governing permissions and
mbed_official 85:e1a8e879a6a9 14 * limitations under the License.
mbed_official 85:e1a8e879a6a9 15 */
mbed_official 85:e1a8e879a6a9 16 #include <stddef.h>
mbed_official 85:e1a8e879a6a9 17 #include "us_ticker_api.h"
mbed_official 85:e1a8e879a6a9 18 #include "cmsis.h"
mbed_official 85:e1a8e879a6a9 19 #include "PeripheralNames.h"
mbed_official 304:89b9c3a9a045 20 #include "app_timer.h"
mbed_official 127:ce7cebc0511f 21
mbed_official 304:89b9c3a9a045 22 static bool us_ticker_inited = false;
mbed_official 304:89b9c3a9a045 23 static volatile bool us_ticker_appTimerRunning = false;
mbed_official 304:89b9c3a9a045 24 static app_timer_id_t us_ticker_appTimerID = TIMER_NULL;
mbed_official 300:55638feb26a4 25
mbed_official 300:55638feb26a4 26 void us_ticker_init(void)
mbed_official 300:55638feb26a4 27 {
mbed_official 304:89b9c3a9a045 28 if (us_ticker_inited) {
mbed_official 85:e1a8e879a6a9 29 return;
mbed_official 85:e1a8e879a6a9 30 }
mbed_official 300:55638feb26a4 31
mbed_official 304:89b9c3a9a045 32 APP_TIMER_INIT(0 /*CFG_TIMER_PRESCALER*/ , 1 /*CFG_TIMER_MAX_INSTANCE*/, 1 /*CFG_TIMER_OPERATION_QUEUE_SIZE*/, false /*CFG_SCHEDULER_ENABLE*/);
mbed_official 300:55638feb26a4 33
mbed_official 304:89b9c3a9a045 34 us_ticker_inited = true;
mbed_official 85:e1a8e879a6a9 35 }
mbed_official 85:e1a8e879a6a9 36
mbed_official 300:55638feb26a4 37 uint32_t us_ticker_read()
mbed_official 300:55638feb26a4 38 {
mbed_official 304:89b9c3a9a045 39 if (!us_ticker_inited) {
mbed_official 304:89b9c3a9a045 40 us_ticker_init();
mbed_official 304:89b9c3a9a045 41 }
mbed_official 304:89b9c3a9a045 42
mbed_official 304:89b9c3a9a045 43 timestamp_t value;
mbed_official 304:89b9c3a9a045 44 app_timer_cnt_get(&value); /* This returns the RTC counter (which is fed by the 32khz crystal clock source) */
mbed_official 304:89b9c3a9a045 45 return (uint32_t)((value * 1000000) / APP_TIMER_CLOCK_FREQ); /* Return a pseudo microsecond counter value.
mbed_official 304:89b9c3a9a045 46 * This is only as precise as the 32khz low-freq
mbed_official 304:89b9c3a9a045 47 * clock source, but could be adequate.*/
mbed_official 304:89b9c3a9a045 48 }
mbed_official 304:89b9c3a9a045 49
mbed_official 304:89b9c3a9a045 50 /* An adaptor to interface us_ticker_irq_handler with the app_timer callback.
mbed_official 304:89b9c3a9a045 51 * Needed because the irq_handler() doesn't take any parameter.*/
mbed_official 304:89b9c3a9a045 52 static void us_ticker_app_timer_callback(void *context)
mbed_official 304:89b9c3a9a045 53 {
mbed_official 304:89b9c3a9a045 54 us_ticker_appTimerRunning = false;
mbed_official 304:89b9c3a9a045 55 us_ticker_irq_handler();
mbed_official 304:89b9c3a9a045 56 }
mbed_official 304:89b9c3a9a045 57
mbed_official 304:89b9c3a9a045 58 void us_ticker_set_interrupt(timestamp_t timestamp)
mbed_official 304:89b9c3a9a045 59 {
mbed_official 304:89b9c3a9a045 60 if (!us_ticker_inited) {
mbed_official 85:e1a8e879a6a9 61 us_ticker_init();
mbed_official 85:e1a8e879a6a9 62 }
mbed_official 300:55638feb26a4 63
mbed_official 304:89b9c3a9a045 64 if (us_ticker_appTimerID == TIMER_NULL) {
mbed_official 304:89b9c3a9a045 65 if (app_timer_create(&us_ticker_appTimerID, APP_TIMER_MODE_SINGLE_SHOT, us_ticker_app_timer_callback) != NRF_SUCCESS) {
mbed_official 304:89b9c3a9a045 66 /* placeholder to do something to recover from error */
mbed_official 304:89b9c3a9a045 67 return;
mbed_official 304:89b9c3a9a045 68 }
mbed_official 300:55638feb26a4 69 }
mbed_official 85:e1a8e879a6a9 70
mbed_official 304:89b9c3a9a045 71 if (us_ticker_appTimerRunning) {
mbed_official 304:89b9c3a9a045 72 return;
mbed_official 300:55638feb26a4 73 }
mbed_official 300:55638feb26a4 74
mbed_official 304:89b9c3a9a045 75 timestamp_t currentCounter64;
mbed_official 304:89b9c3a9a045 76 app_timer_cnt_get(&currentCounter64);
mbed_official 304:89b9c3a9a045 77 uint32_t currentCounter = currentCounter64 & MAX_RTC_COUNTER_VAL;
mbed_official 304:89b9c3a9a045 78 uint32_t targetCounter = ((uint32_t)((timestamp * (uint64_t)APP_TIMER_CLOCK_FREQ) / 1000000) + 1) & MAX_RTC_COUNTER_VAL;
mbed_official 304:89b9c3a9a045 79 uint32_t ticksToCount = (targetCounter >= currentCounter) ?
mbed_official 304:89b9c3a9a045 80 (targetCounter - currentCounter) : (MAX_RTC_COUNTER_VAL + 1) - (currentCounter - targetCounter);
mbed_official 304:89b9c3a9a045 81 if (ticksToCount > 0) {
mbed_official 304:89b9c3a9a045 82 uint32_t rc;
mbed_official 304:89b9c3a9a045 83 rc = app_timer_start(us_ticker_appTimerID, ticksToCount, NULL /*p_context*/);
mbed_official 304:89b9c3a9a045 84 if (rc != NRF_SUCCESS) {
mbed_official 304:89b9c3a9a045 85 /* placeholder to do something to recover from error */
mbed_official 304:89b9c3a9a045 86 return;
mbed_official 300:55638feb26a4 87 }
mbed_official 304:89b9c3a9a045 88 us_ticker_appTimerRunning = true;
mbed_official 300:55638feb26a4 89 }
mbed_official 85:e1a8e879a6a9 90 }
mbed_official 85:e1a8e879a6a9 91
mbed_official 300:55638feb26a4 92 void us_ticker_disable_interrupt(void)
mbed_official 300:55638feb26a4 93 {
mbed_official 304:89b9c3a9a045 94 if (us_ticker_appTimerRunning) {
mbed_official 304:89b9c3a9a045 95 app_timer_stop(us_ticker_appTimerID);
mbed_official 304:89b9c3a9a045 96 }
mbed_official 85:e1a8e879a6a9 97 }
mbed_official 300:55638feb26a4 98
mbed_official 300:55638feb26a4 99 void us_ticker_clear_interrupt(void)
mbed_official 300:55638feb26a4 100 {
mbed_official 304:89b9c3a9a045 101 if (us_ticker_appTimerRunning) {
mbed_official 304:89b9c3a9a045 102 app_timer_stop(us_ticker_appTimerID);
mbed_official 304:89b9c3a9a045 103 }
mbed_official 85:e1a8e879a6a9 104 }