133 lines
3.3 KiB
C
133 lines
3.3 KiB
C
/*
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Copyright (c) 2015 Arduino LLC. All right reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "delay.h"
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#include "Arduino.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** Tick Counter united by ms */
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static volatile uint32_t _ulTickCount=0 ;
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unsigned long millis( void )
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{
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// todo: ensure no interrupts
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return _ulTickCount ;
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}
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// Interrupt-compatible version of micros
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// Theory: repeatedly take readings of SysTick counter, millis counter and SysTick interrupt pending flag.
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// When it appears that millis counter and pending is stable and SysTick hasn't rolled over, use these
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// values to calculate micros. If there is a pending SysTick, add one to the millis counter in the calculation.
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unsigned long micros( void )
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{
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uint32_t ticks, ticks2;
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uint32_t pend, pend2;
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uint32_t count, count2;
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ticks2 = SysTick->VAL;
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pend2 = !!(SCB->ICSR & SCB_ICSR_PENDSTSET_Msk) ;
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count2 = _ulTickCount ;
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do
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{
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ticks=ticks2;
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pend=pend2;
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count=count2;
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ticks2 = SysTick->VAL;
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pend2 = !!(SCB->ICSR & SCB_ICSR_PENDSTSET_Msk) ;
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count2 = _ulTickCount ;
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} while ((pend != pend2) || (count != count2) || (ticks < ticks2));
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return ((count+pend) * 1000) + (((SysTick->LOAD - ticks)*(1048576/(VARIANT_MCK/1000000)))>>20) ;
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// this is an optimization to turn a runtime division into two compile-time divisions and
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// a runtime multiplication and shift, saving a few cycles
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}
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#ifdef __SAMD51__
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/*
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* On SAMD51, use the (32bit) cycle count maintained by the DWT unit,
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* and count exact number of cycles elapsed, rather than guessing how
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* many cycles a loop takes, which is dangerous in the presence of
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* cache. The overhead of the call and internal code is "about" 20
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* cycles. (at 120MHz, that's about 1/6 us)
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*/
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void delayMicroseconds(unsigned int us)
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{
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uint32_t start, elapsed;
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uint32_t count;
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if (us == 0)
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return;
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count = us * (VARIANT_MCK / 1000000) - 20; // convert us to cycles.
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start = DWT->CYCCNT; //CYCCNT is 32bits, takes 37s or so to wrap.
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while (1) {
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elapsed = DWT->CYCCNT - start;
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if (elapsed >= count)
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return;
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}
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}
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#endif
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void delay( unsigned long ms )
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{
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if (ms == 0)
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{
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return;
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}
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uint32_t start = micros();
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while (ms > 0)
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{
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yield();
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while (ms > 0 && (micros() - start) >= 1000)
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{
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ms--;
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start += 1000;
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}
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}
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}
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#include "Reset.h" // for tickReset()
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void SysTick_DefaultHandler(void)
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{
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// Increment tick count each ms
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_ulTickCount++;
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tickReset();
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}
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#if defined(USE_TINYUSB)
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// run TinyUSB background task when yield()
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void yield(void)
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{
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TinyUSB_Device_Task();
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TinyUSB_Device_FlushCDC();
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}
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#endif
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#ifdef __cplusplus
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}
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#endif
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