tmk_core/tool/mbed/mbed-sdk/libraries/mbed/common/us_ticker_api.c

   1 /* mbed Microcontroller Library
   2  * Copyright (c) 2006-2013 ARM Limited
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 #include <stddef.h>
  17 #include "us_ticker_api.h"
  18 #include "cmsis.h"
  19
  20 static ticker_event_handler event_handler;
  21 static ticker_event_t *head = NULL;
  22
  23 void us_ticker_set_handler(ticker_event_handler handler) {
  24     us_ticker_init();
  25
  26     event_handler = handler;
  27 }
  28
  29 void us_ticker_irq_handler(void) {
  30     us_ticker_clear_interrupt();
  31
  32     /* Go through all the pending TimerEvents */
  33     while (1) {
  34         if (head == NULL) {
  35             // There are no more TimerEvents left, so disable matches.
  36             us_ticker_disable_interrupt();
  37             return;
  38         }
  39
  40         if ((int)(head->timestamp - us_ticker_read()) <= 0) {
  41             // This event was in the past:
  42             //      point to the following one and execute its handler
  43             ticker_event_t *p = head;
  44             head = head->next;
  45             if (event_handler != NULL) {
  46                 event_handler(p->id); // NOTE: the handler can set new events
  47             }
  48             /* Note: We continue back to examining the head because calling the
  49              * event handler may have altered the chain of pending events. */
  50         } else {
  51             // This event and the following ones in the list are in the future:
  52             //      set it as next interrupt and return
  53             us_ticker_set_interrupt(head->timestamp);
  54             return;
  55         }
  56     }
  57 }
  58
  59 void us_ticker_insert_event(ticker_event_t *obj, timestamp_t timestamp, uint32_t id) {
  60     /* disable interrupts for the duration of the function */
  61     __disable_irq();
  62
  63     // initialise our data
  64     obj->timestamp = timestamp;
  65     obj->id = id;
  66
  67     /* Go through the list until we either reach the end, or find
  68        an element this should come before (which is possibly the
  69        head). */
  70     ticker_event_t *prev = NULL, *p = head;
  71     while (p != NULL) {
  72         /* check if we come before p */
  73         if ((int)(timestamp - p->timestamp) < 0) {
  74             break;
  75         }
  76         /* go to the next element */
  77         prev = p;
  78         p = p->next;
  79     }
  80
  81     /* if we're at the end p will be NULL, which is correct */
  82     obj->next = p;
  83
  84     /* if prev is NULL we're at the head */
  85     if (prev == NULL) {
  86         head = obj;
  87         us_ticker_set_interrupt(timestamp);
  88     } else {
  89         prev->next = obj;
  90     }
  91
  92     __enable_irq();
  93 }
  94
  95 void us_ticker_remove_event(ticker_event_t *obj) {
  96     __disable_irq();
  97
  98     // remove this object from the list
  99     if (head == obj) {
 100         // first in the list, so just drop me
 101         head = obj->next;
 102         if (head == NULL) {
 103             us_ticker_disable_interrupt();
 104         } else {
 105             us_ticker_set_interrupt(head->timestamp);
 106         }
 107     } else {
 108         // find the object before me, then drop me
 109         ticker_event_t* p = head;
 110         while (p != NULL) {
 111             if (p->next == obj) {
 112                 p->next = obj->next;
 113                 break;
 114             }
 115             p = p->next;
 116         }
 117     }
 118
 119     __enable_irq();
 120 }
 121
 122 int us_ticker_get_next_timestamp(timestamp_t *timestamp) {
 123     int ret = 0;
 124
 125     /* if head is NULL, there are no pending events */
 126     __disable_irq();
 127     if (head != NULL) {
 128         *timestamp = head->timestamp;
 129         ret = 1;
 130     }
 131     __enable_irq();
 132
 133     return ret;
 134 }