Ken Todotani / mbed-src

mbed library sources

Fork of mbed-src by mbed official

targets/hal/TARGET_NXP/TARGET_LPC81X/us_ticker.c@304:89b9c3a9a045, 2014-08-29 (annotated)

Committer:
mbed_official
Date:
Fri Aug 29 17:15:07 2014 +0100
Revision:
304:89b9c3a9a045
Parent:
46:bebbbd80dd87 
Synchronized with git revision 734f365d7da26ef199751f4b0d91611479b495ea



Full URL: https://github.com/mbedmicro/mbed/commit/734f365d7da26ef199751f4b0d91611479b495ea/



1. timestamp_t as an abstraction for time values managed by

   Ticker. Using uint64_t for timestamp_t allows a wraparound-free

   Ticker. This change forces us to update the definitions of usTicker

   for all platforms; but the changes beyond nRF51822 aren't major.



2. reduce power consumption on the nRF51822 by removing the need for

   the high-frequency processor timer; and reimplementing it using the

   RTC.



I've also replaced high-frequency clock with low-frequency external

clock during system startup of the nRF51822. This brings a major win

in power consumption.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mbed_official 46:bebbbd80dd87 1 /* mbed Microcontroller Library
mbed_official 46:bebbbd80dd87 2 * Copyright (c) 2006-2013 ARM Limited
mbed_official 46:bebbbd80dd87 3 *
mbed_official 46:bebbbd80dd87 4 * Licensed under the Apache License, Version 2.0 (the "License");
mbed_official 46:bebbbd80dd87 5 * you may not use this file except in compliance with the License.
mbed_official 46:bebbbd80dd87 6 * You may obtain a copy of the License at
mbed_official 46:bebbbd80dd87 7 *
mbed_official 46:bebbbd80dd87 8 * http://www.apache.org/licenses/LICENSE-2.0
mbed_official 46:bebbbd80dd87 9 *
mbed_official 46:bebbbd80dd87 10 * Unless required by applicable law or agreed to in writing, software
mbed_official 46:bebbbd80dd87 11 * distributed under the License is distributed on an "AS IS" BASIS,
mbed_official 46:bebbbd80dd87 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
mbed_official 46:bebbbd80dd87 13 * See the License for the specific language governing permissions and
mbed_official 46:bebbbd80dd87 14 * limitations under the License.
mbed_official 46:bebbbd80dd87 15 */
mbed_official 46:bebbbd80dd87 16 #include <stddef.h>
mbed_official 46:bebbbd80dd87 17 #include "us_ticker_api.h"
mbed_official 46:bebbbd80dd87 18 #include "PeripheralNames.h"
mbed_official 46:bebbbd80dd87 19
mbed_official 46:bebbbd80dd87 20 #define US_TICKER_TIMER_IRQn SCT_IRQn
mbed_official 46:bebbbd80dd87 21
mbed_official 46:bebbbd80dd87 22 int us_ticker_inited = 0;
mbed_official 46:bebbbd80dd87 23
mbed_official 46:bebbbd80dd87 24 void us_ticker_init(void) {
mbed_official 46:bebbbd80dd87 25 if (us_ticker_inited) return;
mbed_official 46:bebbbd80dd87 26 us_ticker_inited = 1;
mbed_official 46:bebbbd80dd87 27
mbed_official 46:bebbbd80dd87 28 // Enable the SCT clock
mbed_official 46:bebbbd80dd87 29 LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 8);
mbed_official 46:bebbbd80dd87 30
mbed_official 46:bebbbd80dd87 31 // Clear peripheral reset the SCT:
mbed_official 46:bebbbd80dd87 32 LPC_SYSCON->PRESETCTRL |= (1 << 8);
mbed_official 46:bebbbd80dd87 33
mbed_official 46:bebbbd80dd87 34 // Unified counter (32 bits)
mbed_official 46:bebbbd80dd87 35 LPC_SCT->CONFIG |= 1;
mbed_official 46:bebbbd80dd87 36
mbed_official 46:bebbbd80dd87 37 // halt and clear the counter
mbed_official 46:bebbbd80dd87 38 LPC_SCT->CTRL_L |= (1 << 2) | (1 << 3);
mbed_official 46:bebbbd80dd87 39
mbed_official 46:bebbbd80dd87 40 // System Clock (12)MHz -> us_ticker (1)MHz
mbed_official 46:bebbbd80dd87 41 LPC_SCT->CTRL_L |= ((SystemCoreClock/1000000 - 1) << 5);
mbed_official 46:bebbbd80dd87 42
mbed_official 46:bebbbd80dd87 43 // unhalt the counter:
mbed_official 46:bebbbd80dd87 44 // - clearing bit 2 of the CTRL register
mbed_official 46:bebbbd80dd87 45 LPC_SCT->CTRL_L &= ~(1 << 2);
mbed_official 46:bebbbd80dd87 46
mbed_official 46:bebbbd80dd87 47 NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
mbed_official 46:bebbbd80dd87 48 NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
mbed_official 46:bebbbd80dd87 49 }
mbed_official 46:bebbbd80dd87 50
mbed_official 46:bebbbd80dd87 51 uint32_t us_ticker_read() {
mbed_official 46:bebbbd80dd87 52 if (!us_ticker_inited)
mbed_official 46:bebbbd80dd87 53 us_ticker_init();
mbed_official 46:bebbbd80dd87 54
mbed_official 46:bebbbd80dd87 55 return LPC_SCT->COUNT_U;
mbed_official 46:bebbbd80dd87 56 }
mbed_official 46:bebbbd80dd87 57
mbed_official 304:89b9c3a9a045 58 void us_ticker_set_interrupt(timestamp_t timestamp) {
mbed_official 46:bebbbd80dd87 59 // halt the counter:
mbed_official 46:bebbbd80dd87 60 // - setting bit 2 of the CTRL register
mbed_official 46:bebbbd80dd87 61 LPC_SCT->CTRL_L |= (1 << 2);
mbed_official 46:bebbbd80dd87 62
mbed_official 46:bebbbd80dd87 63 // set timestamp in compare register
mbed_official 304:89b9c3a9a045 64 LPC_SCT->MATCH[0].U = (uint32_t)timestamp;
mbed_official 46:bebbbd80dd87 65
mbed_official 46:bebbbd80dd87 66 // unhalt the counter:
mbed_official 46:bebbbd80dd87 67 // - clearing bit 2 of the CTRL register
mbed_official 46:bebbbd80dd87 68 LPC_SCT->CTRL_L &= ~(1 << 2);
mbed_official 46:bebbbd80dd87 69
mbed_official 46:bebbbd80dd87 70 // if events are not enabled, enable them
mbed_official 46:bebbbd80dd87 71 if (!(LPC_SCT->EVEN & 0x01)) {
mbed_official 46:bebbbd80dd87 72
mbed_official 46:bebbbd80dd87 73 // comb mode = match only
mbed_official 46:bebbbd80dd87 74 LPC_SCT->EVENT[0].CTRL = (1 << 12);
mbed_official 46:bebbbd80dd87 75
mbed_official 46:bebbbd80dd87 76 // ref manual:
mbed_official 46:bebbbd80dd87 77 // In simple applications that do not
mbed_official 46:bebbbd80dd87 78 // use states, write 0x01 to this
mbed_official 46:bebbbd80dd87 79 // register to enable an event
mbed_official 46:bebbbd80dd87 80 LPC_SCT->EVENT[0].STATE |= 0x1;
mbed_official 46:bebbbd80dd87 81
mbed_official 46:bebbbd80dd87 82 // enable events
mbed_official 46:bebbbd80dd87 83 LPC_SCT->EVEN |= 0x1;
mbed_official 46:bebbbd80dd87 84 }
mbed_official 46:bebbbd80dd87 85 }
mbed_official 46:bebbbd80dd87 86
mbed_official 46:bebbbd80dd87 87 void us_ticker_disable_interrupt(void) {
mbed_official 46:bebbbd80dd87 88 LPC_SCT->EVEN &= ~1;
mbed_official 46:bebbbd80dd87 89 }
mbed_official 46:bebbbd80dd87 90
mbed_official 46:bebbbd80dd87 91 void us_ticker_clear_interrupt(void) {
mbed_official 46:bebbbd80dd87 92 LPC_SCT->EVFLAG = 1;
mbed_official 46:bebbbd80dd87 93 }