mirror of https://github.com/ARMmbed/mbed-os.git
84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
/* mbed Microcontroller Library
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* Copyright (c) 2006-2013 ARM Limited
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <stddef.h>
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#include "us_ticker_api.h"
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#include "PeripheralNames.h"
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#include "mbed_critical.h"
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#define US_TICKER_TIMER_IRQn SCT3_IRQn
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int us_ticker_inited = 0;
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void us_ticker_init(void) {
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if (us_ticker_inited)
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return;
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us_ticker_inited = 1;
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// Enable the SCT3 clock
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LPC_SYSCON->SYSAHBCLKCTRL1 |= (1 << 5);
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// Clear peripheral reset the SCT3
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LPC_SYSCON->PRESETCTRL1 |= (1 << 5);
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LPC_SYSCON->PRESETCTRL1 &= ~(1 << 5);
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// Configure SCT3 as a 1MHz 32-bit counter with no auto limiting or match reload
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char sctClkDiv = ((SystemCoreClock + 1000000 - 1) / 1000000) - 1;
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LPC_SCT3->CONFIG = (1 << 7) | (1 << 0);
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LPC_SCT3->CTRL = (sctClkDiv << 5) | (1 << 3) | (1 << 2);
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// Configure SCT3 event 0 to fire on match register 0
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LPC_SCT3->EV0_STATE = (1 << 0);
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LPC_SCT3->EV0_CTRL = (0x1 << 12);
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// Start SCT3
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LPC_SCT3->CTRL &= ~(1 << 2);
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// Set SCT3 interrupt vector
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NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
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NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
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}
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uint32_t us_ticker_read() {
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if (!us_ticker_inited)
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us_ticker_init();
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// Return SCT3 count value
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return LPC_SCT3->COUNT;
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}
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void us_ticker_set_interrupt(timestamp_t timestamp) {
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// Set SCT3 match register 0 (critical section)
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core_util_critical_section_enter();
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LPC_SCT3->CTRL |= (1 << 2);
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LPC_SCT3->MATCH0 = (uint32_t)timestamp;
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LPC_SCT3->CTRL &= ~(1 << 2);
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core_util_critical_section_exit();
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// Enable interrupt on SCT3 event 0
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LPC_SCT3->EVEN = (1 << 0);
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}
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void us_ticker_disable_interrupt(void) {
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// Disable interrupt on SCT3 event 0
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LPC_SCT3->EVEN = 0;
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}
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void us_ticker_clear_interrupt(void) {
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// Clear SCT3 event 0 interrupt flag
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LPC_SCT3->EVFLAG = (1 << 0);
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}
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