Lancaster University / mbed-src

Lancaster University's (short term!) clone of mbed-src for micro:bit. This is a copy of the github branch https://github.com/lancaster-university/mbed-classic

Fork of mbed-src by mbed official

common/Timer.cpp@641:be9b2017785a, 2016-07-13 (annotated)

Committer:
LancasterUniversity
Date:
Wed Jul 13 12:52:54 2016 +0100
Revision:
641:be9b2017785a
Parent:
547:88c982c8f758 
Synchronized with git rev 1fb8ab4c

Author: James Devine

mbed-classic: BUGFIX for timer when using wait_ms from interrupt context



Previously if a user used wait[_ms,_us] in interrupt context the device would

hang indefinitely. This was due to incrementing overflowCount from

interrupt context only.



This meant that if a user used wait[_ms,_us] in an ISR with

the same or greater interrupt priority, it would result in an infinite

loop as the overflowCount variable would never be incremented, and

wait[_ms,_us] would never return.



This patch simply applies a better solution for the race condition

mentioned in the previous commit. It instead disables the timer1

interrupt and increments the overflowCount variable, preventing

the race condition whilst supporting wait[_ms,_us] in interrupt

context.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
bogdanm 13:0645d8841f51 1 /* mbed Microcontroller Library
bogdanm 13:0645d8841f51 2 * Copyright (c) 2006-2013 ARM Limited
bogdanm 13:0645d8841f51 3 *
bogdanm 13:0645d8841f51 4 * Licensed under the Apache License, Version 2.0 (the "License");
bogdanm 13:0645d8841f51 5 * you may not use this file except in compliance with the License.
bogdanm 13:0645d8841f51 6 * You may obtain a copy of the License at
bogdanm 13:0645d8841f51 7 *
bogdanm 13:0645d8841f51 8 * http://www.apache.org/licenses/LICENSE-2.0
bogdanm 13:0645d8841f51 9 *
bogdanm 13:0645d8841f51 10 * Unless required by applicable law or agreed to in writing, software
bogdanm 13:0645d8841f51 11 * distributed under the License is distributed on an "AS IS" BASIS,
bogdanm 13:0645d8841f51 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
bogdanm 13:0645d8841f51 13 * See the License for the specific language governing permissions and
bogdanm 13:0645d8841f51 14 * limitations under the License.
bogdanm 13:0645d8841f51 15 */
bogdanm 13:0645d8841f51 16 #include "Timer.h"
mbed_official 525:c320967f86b9 17 #include "ticker_api.h"
bogdanm 13:0645d8841f51 18 #include "us_ticker_api.h"
bogdanm 13:0645d8841f51 19
bogdanm 13:0645d8841f51 20 namespace mbed {
bogdanm 13:0645d8841f51 21
mbed_official 525:c320967f86b9 22 Timer::Timer() : _running(), _start(), _time(), _ticker_data(get_us_ticker_data()) {
mbed_official 525:c320967f86b9 23 reset();
mbed_official 525:c320967f86b9 24 }
mbed_official 525:c320967f86b9 25
mbed_official 547:88c982c8f758 26 Timer::Timer(const ticker_data_t *data) : _running(), _start(), _time(), _ticker_data(data) {
bogdanm 13:0645d8841f51 27 reset();
bogdanm 13:0645d8841f51 28 }
bogdanm 13:0645d8841f51 29
bogdanm 13:0645d8841f51 30 void Timer::start() {
mbed_official 358:9d7ef901f004 31 if (!_running) {
mbed_official 525:c320967f86b9 32 _start = ticker_read(_ticker_data);
mbed_official 358:9d7ef901f004 33 _running = 1;
mbed_official 358:9d7ef901f004 34 }
bogdanm 13:0645d8841f51 35 }
bogdanm 13:0645d8841f51 36
bogdanm 13:0645d8841f51 37 void Timer::stop() {
bogdanm 13:0645d8841f51 38 _time += slicetime();
bogdanm 13:0645d8841f51 39 _running = 0;
bogdanm 13:0645d8841f51 40 }
bogdanm 13:0645d8841f51 41
bogdanm 13:0645d8841f51 42 int Timer::read_us() {
bogdanm 13:0645d8841f51 43 return _time + slicetime();
bogdanm 13:0645d8841f51 44 }
bogdanm 13:0645d8841f51 45
bogdanm 13:0645d8841f51 46 float Timer::read() {
bogdanm 13:0645d8841f51 47 return (float)read_us() / 1000000.0f;
bogdanm 13:0645d8841f51 48 }
bogdanm 13:0645d8841f51 49
bogdanm 13:0645d8841f51 50 int Timer::read_ms() {
bogdanm 13:0645d8841f51 51 return read_us() / 1000;
bogdanm 13:0645d8841f51 52 }
bogdanm 13:0645d8841f51 53
bogdanm 13:0645d8841f51 54 int Timer::slicetime() {
bogdanm 13:0645d8841f51 55 if (_running) {
mbed_official 525:c320967f86b9 56 return ticker_read(_ticker_data) - _start;
bogdanm 13:0645d8841f51 57 } else {
bogdanm 13:0645d8841f51 58 return 0;
bogdanm 13:0645d8841f51 59 }
bogdanm 13:0645d8841f51 60 }
bogdanm 13:0645d8841f51 61
bogdanm 13:0645d8841f51 62 void Timer::reset() {
mbed_official 525:c320967f86b9 63 _start = ticker_read(_ticker_data);
bogdanm 13:0645d8841f51 64 _time = 0;
bogdanm 13:0645d8841f51 65 }
bogdanm 13:0645d8841f51 66
bogdanm 13:0645d8841f51 67 #ifdef MBED_OPERATORS
bogdanm 13:0645d8841f51 68 Timer::operator float() {
bogdanm 13:0645d8841f51 69 return read();
bogdanm 13:0645d8841f51 70 }
bogdanm 13:0645d8841f51 71 #endif
bogdanm 13:0645d8841f51 72
bogdanm 13:0645d8841f51 73 } // namespace mbed