Forked mbed-dev as I use an 20 pins stm32F042 and not the 32 pins version
Fork of mbed-dev by
targets/TARGET_NXP/TARGET_LPC82X/us_ticker.c
- Committer:
- <>
- Date:
- 2016-10-28
- Revision:
- 149:156823d33999
- Parent:
- targets/hal/TARGET_NXP/TARGET_LPC82X/us_ticker.c@ 144:ef7eb2e8f9f7
File content as of revision 149:156823d33999:
/* mbed Microcontroller Library * Copyright (c) 2006-2013 ARM Limited * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #include <stddef.h> #include "us_ticker_api.h" #include "PeripheralNames.h" static int us_ticker_inited = 0; int MRT_Clock_MHz; unsigned int ticker_fullcount_us; unsigned long int ticker_expired_count_us = 0; #define US_TICKER_TIMER_IRQn MRT_IRQn void us_ticker_init(void) { if (us_ticker_inited) return; us_ticker_inited = 1; // Calculate MRT clock value (MRT has no prescaler) MRT_Clock_MHz = (SystemCoreClock / 1000000); // Calculate fullcounter value in us (MRT has 31 bits and clock is 30MHz) ticker_fullcount_us = 0x80000000UL/MRT_Clock_MHz; // Enable the MRT clock LPC_SYSCON->SYSAHBCLKCTRL |= (1 << 10); // Clear peripheral reset the MRT LPC_SYSCON->PRESETCTRL |= (1 << 7); // Force load interval value (Bit 0-30 is interval value, Bit 31 is Force Load bit) LPC_MRT->INTVAL0 = 0xFFFFFFFFUL; // Enable Ch0 interrupt, Mode 0 is Repeat Interrupt LPC_MRT->CTRL0 = (0x0 << 1) | (0x1 << 0); // Force load interval value (Bit 0-30 is interval value, Bit 31 is Force Load bit) LPC_MRT->INTVAL1 = 0x80000000UL; // Disable ch1 interrupt, Mode 0 is Repeat Interrupt LPC_MRT->CTRL1 = (0x0 << 1) | (0x0 << 0); // Set MRT interrupt vector NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler); NVIC_EnableIRQ(US_TICKER_TIMER_IRQn); } //TIMER0 is used for us ticker and timers (Timer, wait(), wait_us() etc) uint32_t us_ticker_read() { if (!us_ticker_inited) us_ticker_init(); // Generate ticker value // MRT source clock is SystemCoreClock (30MHz) and MRT is a 31-bit countdown timer // Calculate expected value using number of expired times to mimic a 32bit timer @ 1 MHz return (0x7FFFFFFFUL - LPC_MRT->TIMER0)/MRT_Clock_MHz + ticker_expired_count_us; } //TIMER1 is used for Timestamped interrupts (Ticker(), Timeout()) void us_ticker_set_interrupt(timestamp_t timestamp) { // MRT source clock is SystemCoreClock (30MHz) and MRT is a 31-bit countdown timer // Force load interval value (Bit 0-30 is interval value, Bit 31 is Force Load bit) // Note: The MRT has less counter headroom available than the typical mbed 32bit timer @ 1 MHz. // The calculated counter interval until the next timestamp will be truncated and an // 'early' interrupt will be generated in case the max required count interval exceeds // the available 31 bits space. However, the mbed us_ticker interrupt handler will // check current time against the next scheduled timestamp and simply re-issue the // same interrupt again when needed. The calculated counter interval will now be smaller. LPC_MRT->INTVAL1 = (((timestamp - us_ticker_read()) * MRT_Clock_MHz) | 0x80000000UL); // Enable interrupt LPC_MRT->CTRL1 |= 1; } //Disable Timestamped interrupts triggered by TIMER1 void us_ticker_disable_interrupt() { //Timer1 for Timestamped interrupts (31 bits downcounter @ SystemCoreClock) LPC_MRT->CTRL1 &= ~1; } void us_ticker_clear_interrupt() { //Timer1 for Timestamped interrupts (31 bits downcounter @ SystemCoreClock) if (LPC_MRT->STAT1 & 1) LPC_MRT->STAT1 = 1; //Timer0 for us counter (31 bits downcounter @ SystemCoreClock) if (LPC_MRT->STAT0 & 1) { LPC_MRT->STAT0 = 1; ticker_expired_count_us += ticker_fullcount_us; } }