tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_STM/TARGET_STM32F4XX/us_ticker.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 "PeripheralNames.h"
  19
  20 #define US_TICKER_TIMER TIM2
  21 #define US_TICKER_TIMER_IRQn TIM2_IRQn
  22
  23 int us_ticker_inited = 0;
  24
  25 void us_ticker_init(void) {
  26     if (us_ticker_inited) return;
  27     us_ticker_inited = 1;
  28
  29     RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;
  30
  31     uint32_t PCLK = SystemCoreClock / 4;
  32
  33     uint32_t prescale = PCLK / 1000000; // default to 1MHz (1 us ticks)
  34     US_TICKER_TIMER->PSC = prescale - 1;
  35     US_TICKER_TIMER->CR1 |= TIM_CR1_CEN;
  36     // Trigger an update - this needs to happen after the counter is enabled.
  37     US_TICKER_TIMER->EGR |= TIM_EGR_UG;
  38
  39     NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
  40     NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
  41 }
  42
  43 uint32_t us_ticker_read() {
  44     if (!us_ticker_inited)
  45         us_ticker_init();
  46
  47     return US_TICKER_TIMER->CNT;
  48 }
  49
  50 void us_ticker_set_interrupt(timestamp_t timestamp) {
  51     // set match value
  52     US_TICKER_TIMER->CCR1 = (uint32_t)timestamp;
  53     // enable compare interrupt
  54     US_TICKER_TIMER->DIER |= TIM_DIER_CC1IE;
  55 }
  56
  57 void us_ticker_disable_interrupt(void) {
  58     US_TICKER_TIMER->DIER &= ~TIM_DIER_CC1IE;
  59 }
  60
  61 void us_ticker_clear_interrupt(void) {
  62     US_TICKER_TIMER->SR &= ~TIM_SR_CC1IF;
  63 }