arm_hal_timer.cpp

00001 /*
00002  * Copyright (c) 2016 ARM Limited, All Rights Reserved
00003  */
00004 
00005 // Include before mbed.h to properly get UINT*_C()
00006 #include "ns_types.h"
00007 
00008 #include "mbed.h"
00009 #include "platform/arm_hal_timer.h"
00010 #include "platform/arm_hal_interrupt.h"
00011 #include <mbed_assert.h>
00012 
00013 static Timer timer;
00014 static Timeout timeout;
00015 static EventQueue *equeue;
00016 static uint32_t due;
00017 static void (*arm_hal_callback)(void);
00018 
00019 // Called once at boot
00020 void platform_timer_enable(void)
00021 {
00022     equeue = mbed_highprio_event_queue();
00023     MBED_ASSERT(equeue != NULL);
00024 }
00025 
00026 // Actually cancels a timer, not the opposite of enable
00027 void platform_timer_disable(void)
00028 {
00029     timeout.detach();
00030 }
00031 
00032 // Not called while running, fortunately
00033 void platform_timer_set_cb(void (*new_fp)(void))
00034 {
00035     arm_hal_callback = new_fp;
00036 }
00037 
00038 static void timer_callback(void)
00039 {
00040     due = 0;
00041     equeue->call(arm_hal_callback);
00042 }
00043 
00044 // This is called from inside platform_enter_critical - IRQs can't happen
00045 void platform_timer_start(uint16_t slots)
00046 {
00047     timer.reset();
00048     due = slots * UINT32_C(50);
00049     timeout.attach_us(timer_callback, due);
00050 }
00051 
00052 // This is called from inside platform_enter_critical - IRQs can't happen
00053 uint16_t platform_timer_get_remaining_slots(void)
00054 {
00055     uint32_t elapsed = timer.read_us();
00056     if (elapsed < due) {
00057         return (uint16_t) ((due - elapsed) / 50);
00058     } else {
00059         return 0;
00060     }
00061 }
00062