1 /* mbed Microcontroller Library
2 * Copyright (c) 2006-2013 ARM Limited
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 #include "us_ticker_api.h"
18 #include "PeripheralNames.h"
20 #define US_TICKER_TIMER TIM2
21 #define US_TICKER_TIMER_IRQn TIM2_IRQn
23 int us_ticker_inited = 0;
25 void us_ticker_init(void) {
26 if (us_ticker_inited) return;
29 RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;
31 uint32_t PCLK = SystemCoreClock / 4;
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;
39 NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
40 NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
43 uint32_t us_ticker_read() {
44 if (!us_ticker_inited)
47 return US_TICKER_TIMER->CNT;
50 void us_ticker_set_interrupt(timestamp_t timestamp) {
52 US_TICKER_TIMER->CCR1 = (uint32_t)timestamp;
53 // enable compare interrupt
54 US_TICKER_TIMER->DIER |= TIM_DIER_CC1IE;
57 void us_ticker_disable_interrupt(void) {
58 US_TICKER_TIMER->DIER &= ~TIM_DIER_CC1IE;
61 void us_ticker_clear_interrupt(void) {
62 US_TICKER_TIMER->SR &= ~TIM_SR_CC1IF;