mbed_ticker_api.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2015 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #include <stddef.h>
00017 #include "hal/ticker_api.h"
00018 #include "platform/mbed_critical.h"
00019 
00020 void ticker_set_handler(const ticker_data_t *const data, ticker_event_handler handler) {
00021     data->interface->init();
00022 
00023     data->queue->event_handler = handler;
00024 }
00025 
00026 void ticker_irq_handler(const ticker_data_t *const data) {
00027     data->interface->clear_interrupt();
00028 
00029     /* Go through all the pending TimerEvents */
00030     while (1) {
00031         if (data->queue->head == NULL) {
00032             // There are no more TimerEvents left, so disable matches.
00033             data->interface->disable_interrupt();
00034             return;
00035         }
00036 
00037         if ((int)(data->queue->head->timestamp - data->interface->read()) <= 0) {
00038             // This event was in the past:
00039             //      point to the following one and execute its handler
00040             ticker_event_t *p = data->queue->head;
00041             data->queue->head = data->queue->head->next;
00042             if (data->queue->event_handler != NULL) {
00043                 (*data->queue->event_handler)(p->id); // NOTE: the handler can set new events
00044             }
00045             /* Note: We continue back to examining the head because calling the
00046              * event handler may have altered the chain of pending events. */
00047         } else {
00048             // This event and the following ones in the list are in the future:
00049             //      set it as next interrupt and return
00050             data->interface->set_interrupt(data->queue->head->timestamp);
00051             return;
00052         }
00053     }
00054 }
00055 
00056 void ticker_insert_event(const ticker_data_t *const data, ticker_event_t *obj, timestamp_t timestamp, uint32_t id) {
00057     /* disable interrupts for the duration of the function */
00058     core_util_critical_section_enter();
00059 
00060     // initialise our data
00061     obj->timestamp = timestamp;
00062     obj->id = id;
00063 
00064     /* Go through the list until we either reach the end, or find
00065        an element this should come before (which is possibly the
00066        head). */
00067     ticker_event_t *prev = NULL, *p = data->queue->head;
00068     while (p != NULL) {
00069         /* check if we come before p */
00070         if ((int)(timestamp - p->timestamp) < 0) {
00071             break;
00072         }
00073         /* go to the next element */
00074         prev = p;
00075         p = p->next;
00076     }
00077     
00078     /* if we're at the end p will be NULL, which is correct */
00079     obj->next = p;
00080 
00081     /* if prev is NULL we're at the head */
00082     if (prev == NULL) {
00083         data->queue->head = obj;
00084         data->interface->set_interrupt(timestamp);
00085     } else {
00086         prev->next = obj;
00087     }
00088 
00089     core_util_critical_section_exit();
00090 }
00091 
00092 void ticker_remove_event(const ticker_data_t *const data, ticker_event_t *obj) {
00093     core_util_critical_section_enter();
00094 
00095     // remove this object from the list
00096     if (data->queue->head == obj) {
00097         // first in the list, so just drop me
00098         data->queue->head = obj->next;
00099         if (data->queue->head == NULL) {
00100             data->interface->disable_interrupt();
00101         } else {
00102             data->interface->set_interrupt(data->queue->head->timestamp);
00103         }
00104     } else {
00105         // find the object before me, then drop me
00106         ticker_event_t* p = data->queue->head;
00107         while (p != NULL) {
00108             if (p->next == obj) {
00109                 p->next = obj->next;
00110                 break;
00111             }
00112             p = p->next;
00113         }
00114     }
00115 
00116     core_util_critical_section_exit();
00117 }
00118 
00119 timestamp_t ticker_read(const ticker_data_t *const data)
00120 {
00121     return data->interface->read();
00122 }
00123 
00124 int ticker_get_next_timestamp(const ticker_data_t *const data, timestamp_t *timestamp)
00125 {
00126     int ret = 0;
00127 
00128     /* if head is NULL, there are no pending events */
00129     core_util_critical_section_enter();
00130     if (data->queue->head != NULL) {
00131         *timestamp = data->queue->head->timestamp;
00132         ret = 1;
00133     }
00134     core_util_critical_section_exit();
00135 
00136     return ret;
00137 }