Umar Naeem / mbed-dev

mbed library sources. Supersedes mbed-src.

Fork of mbed-dev by Umar Naeem

targets/TARGET_NXP/TARGET_LPC82X/us_ticker.c@165:2dd56e6daeec, 2017-05-23 (annotated)

Committer:
ranaumarnaeem
Date:
Tue May 23 12:54:50 2017 +0000
Revision:
165:2dd56e6daeec
Parent:
149:156823d33999 
jhjg

Who changed what in which revision?

UserRevisionLine numberNew contents of line
<> 144:ef7eb2e8f9f7 1 /* mbed Microcontroller Library
<> 144:ef7eb2e8f9f7 2 * Copyright (c) 2006-2013 ARM Limited
<> 144:ef7eb2e8f9f7 3 *
<> 144:ef7eb2e8f9f7 4 * Licensed under the Apache License, Version 2.0 (the "License");
<> 144:ef7eb2e8f9f7 5 * you may not use this file except in compliance with the License.
<> 144:ef7eb2e8f9f7 6 * You may obtain a copy of the License at
<> 144:ef7eb2e8f9f7 7 *
<> 144:ef7eb2e8f9f7 8 * http://www.apache.org/licenses/LICENSE-2.0
<> 144:ef7eb2e8f9f7 9 *
<> 144:ef7eb2e8f9f7 10 * Unless required by applicable law or agreed to in writing, software
<> 144:ef7eb2e8f9f7 11 * distributed under the License is distributed on an "AS IS" BASIS,
<> 144:ef7eb2e8f9f7 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
<> 144:ef7eb2e8f9f7 13 * See the License for the specific language governing permissions and
<> 144:ef7eb2e8f9f7 14 * limitations under the License.
<> 144:ef7eb2e8f9f7 15 */
<> 144:ef7eb2e8f9f7 16 #include <stddef.h>
<> 144:ef7eb2e8f9f7 17 #include "us_ticker_api.h"
<> 144:ef7eb2e8f9f7 18 #include "PeripheralNames.h"
<> 144:ef7eb2e8f9f7 19
<> 144:ef7eb2e8f9f7 20 static int us_ticker_inited = 0;
<> 144:ef7eb2e8f9f7 21 int MRT_Clock_MHz;
<> 144:ef7eb2e8f9f7 22 unsigned int ticker_fullcount_us;
<> 144:ef7eb2e8f9f7 23 unsigned long int ticker_expired_count_us = 0;
<> 144:ef7eb2e8f9f7 24
<> 144:ef7eb2e8f9f7 25 #define US_TICKER_TIMER_IRQn MRT_IRQn
<> 144:ef7eb2e8f9f7 26
<> 144:ef7eb2e8f9f7 27 void us_ticker_init(void) {
<> 144:ef7eb2e8f9f7 28
<> 144:ef7eb2e8f9f7 29 if (us_ticker_inited)
<> 144:ef7eb2e8f9f7 30 return;
<> 144:ef7eb2e8f9f7 31
<> 144:ef7eb2e8f9f7 32 us_ticker_inited = 1;
<> 144:ef7eb2e8f9f7 33
<> 144:ef7eb2e8f9f7 34 // Calculate MRT clock value (MRT has no prescaler)
<> 144:ef7eb2e8f9f7 35 MRT_Clock_MHz = (SystemCoreClock / 1000000);
<> 144:ef7eb2e8f9f7 36 // Calculate fullcounter value in us (MRT has 31 bits and clock is 30MHz)
<> 144:ef7eb2e8f9f7 37 ticker_fullcount_us = 0x80000000UL/MRT_Clock_MHz;
<> 144:ef7eb2e8f9f7 38
<> 144:ef7eb2e8f9f7 39 // Enable the MRT clock
<> 144:ef7eb2e8f9f7 40 LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 10);
<> 144:ef7eb2e8f9f7 41
<> 144:ef7eb2e8f9f7 42 // Clear peripheral reset the MRT
<> 144:ef7eb2e8f9f7 43 LPC_SYSCON->PRESETCTRL |= (1 << 7);
<> 144:ef7eb2e8f9f7 44
<> 144:ef7eb2e8f9f7 45 // Force load interval value (Bit 0-30 is interval value, Bit 31 is Force Load bit)
<> 144:ef7eb2e8f9f7 46 LPC_MRT->INTVAL0 = 0xFFFFFFFFUL;
<> 144:ef7eb2e8f9f7 47 // Enable Ch0 interrupt, Mode 0 is Repeat Interrupt
<> 144:ef7eb2e8f9f7 48 LPC_MRT->CTRL0 = (0x0 << 1) | (0x1 << 0);
<> 144:ef7eb2e8f9f7 49
<> 144:ef7eb2e8f9f7 50 // Force load interval value (Bit 0-30 is interval value, Bit 31 is Force Load bit)
<> 144:ef7eb2e8f9f7 51 LPC_MRT->INTVAL1 = 0x80000000UL;
<> 144:ef7eb2e8f9f7 52 // Disable ch1 interrupt, Mode 0 is Repeat Interrupt
<> 144:ef7eb2e8f9f7 53 LPC_MRT->CTRL1 = (0x0 << 1) | (0x0 << 0);
<> 144:ef7eb2e8f9f7 54
<> 144:ef7eb2e8f9f7 55 // Set MRT interrupt vector
<> 144:ef7eb2e8f9f7 56 NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
<> 144:ef7eb2e8f9f7 57 NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
<> 144:ef7eb2e8f9f7 58 }
<> 144:ef7eb2e8f9f7 59
<> 144:ef7eb2e8f9f7 60 //TIMER0 is used for us ticker and timers (Timer, wait(), wait_us() etc)
<> 144:ef7eb2e8f9f7 61 uint32_t us_ticker_read() {
<> 144:ef7eb2e8f9f7 62
<> 144:ef7eb2e8f9f7 63 if (!us_ticker_inited)
<> 144:ef7eb2e8f9f7 64 us_ticker_init();
<> 144:ef7eb2e8f9f7 65
<> 144:ef7eb2e8f9f7 66 // Generate ticker value
<> 144:ef7eb2e8f9f7 67 // MRT source clock is SystemCoreClock (30MHz) and MRT is a 31-bit countdown timer
<> 144:ef7eb2e8f9f7 68 // Calculate expected value using number of expired times to mimic a 32bit timer @ 1 MHz
<> 144:ef7eb2e8f9f7 69 return (0x7FFFFFFFUL - LPC_MRT->TIMER0)/MRT_Clock_MHz + ticker_expired_count_us;
<> 144:ef7eb2e8f9f7 70 }
<> 144:ef7eb2e8f9f7 71
<> 144:ef7eb2e8f9f7 72 //TIMER1 is used for Timestamped interrupts (Ticker(), Timeout())
<> 144:ef7eb2e8f9f7 73 void us_ticker_set_interrupt(timestamp_t timestamp) {
<> 144:ef7eb2e8f9f7 74
<> 144:ef7eb2e8f9f7 75 // MRT source clock is SystemCoreClock (30MHz) and MRT is a 31-bit countdown timer
<> 144:ef7eb2e8f9f7 76 // Force load interval value (Bit 0-30 is interval value, Bit 31 is Force Load bit)
<> 144:ef7eb2e8f9f7 77 // Note: The MRT has less counter headroom available than the typical mbed 32bit timer @ 1 MHz.
<> 144:ef7eb2e8f9f7 78 // The calculated counter interval until the next timestamp will be truncated and an
<> 144:ef7eb2e8f9f7 79 // 'early' interrupt will be generated in case the max required count interval exceeds
<> 144:ef7eb2e8f9f7 80 // the available 31 bits space. However, the mbed us_ticker interrupt handler will
<> 144:ef7eb2e8f9f7 81 // check current time against the next scheduled timestamp and simply re-issue the
<> 144:ef7eb2e8f9f7 82 // same interrupt again when needed. The calculated counter interval will now be smaller.
<> 144:ef7eb2e8f9f7 83 LPC_MRT->INTVAL1 = (((timestamp - us_ticker_read()) * MRT_Clock_MHz) | 0x80000000UL);
<> 144:ef7eb2e8f9f7 84
<> 144:ef7eb2e8f9f7 85 // Enable interrupt
<> 144:ef7eb2e8f9f7 86 LPC_MRT->CTRL1 |= 1;
<> 144:ef7eb2e8f9f7 87 }
<> 144:ef7eb2e8f9f7 88
<> 144:ef7eb2e8f9f7 89 //Disable Timestamped interrupts triggered by TIMER1
<> 144:ef7eb2e8f9f7 90 void us_ticker_disable_interrupt() {
<> 144:ef7eb2e8f9f7 91 //Timer1 for Timestamped interrupts (31 bits downcounter @ SystemCoreClock)
<> 144:ef7eb2e8f9f7 92 LPC_MRT->CTRL1 &= ~1;
<> 144:ef7eb2e8f9f7 93 }
<> 144:ef7eb2e8f9f7 94
<> 144:ef7eb2e8f9f7 95 void us_ticker_clear_interrupt() {
<> 144:ef7eb2e8f9f7 96
<> 144:ef7eb2e8f9f7 97 //Timer1 for Timestamped interrupts (31 bits downcounter @ SystemCoreClock)
<> 144:ef7eb2e8f9f7 98 if (LPC_MRT->STAT1 & 1)
<> 144:ef7eb2e8f9f7 99 LPC_MRT->STAT1 = 1;
<> 144:ef7eb2e8f9f7 100
<> 144:ef7eb2e8f9f7 101 //Timer0 for us counter (31 bits downcounter @ SystemCoreClock)
<> 144:ef7eb2e8f9f7 102 if (LPC_MRT->STAT0 & 1) {
<> 144:ef7eb2e8f9f7 103 LPC_MRT->STAT0 = 1;
<> 144:ef7eb2e8f9f7 104 ticker_expired_count_us += ticker_fullcount_us;
<> 144:ef7eb2e8f9f7 105 }
<> 144:ef7eb2e8f9f7 106 }