1 /* 2 * Copyright (c) 2015, Freescale Semiconductor, Inc. 3 * Copyright 2016-2017 NXP 4 * All rights reserved. 5 * 6 * SPDX-License-Identifier: BSD-3-Clause 7 */ 8 9 /*! \file driver_systick.c 10 \brief Encapsulates the ARM sysTick counter, which is used for benchmarking 11 */ 12 13 #include "sensor_fusion.h" 14 #include "drivers.h" 15 16 // SysTick register definitions based on CMSIS definitions for same 17 #define SYST_CSR SysTick->CTRL // SysTick Control & Status Register 18 #define SYST_RVR SysTick->LOAD // SysTick Reload Value Register 19 #define SYST_CVR SysTick->VAL // SysTick Current Value Register 20 21 // ARM-core specific function that enables the ARM systick timer on Kinetis uCs. 22 // this is purely for algorithm benchmarking and can either be deleted or re-written for use on other uCs. 23 // the systick clock frequency for each uC are defined as CORE_SYSTICK_HZ in types.h. 24 25 // the timer is 24 bit so allows measurement of intervals up to 2^24/CORE_SYSTICK_HZ secs=0.35s for a 48MHz uC. ARM_systick_enable(void)26void ARM_systick_enable(void) 27 { 28 SYST_CSR = 0x5u; // enable systick from internal clock 29 SYST_RVR = 0x00FFFFFFu; // set reload to maximum 24 bit value 30 return; 31 } 32 33 // ARM-core specific function to store the current systick timer ticks for benchmarking ARM_systick_start_ticks(int32 * pstart)34void ARM_systick_start_ticks(int32 *pstart) 35 { 36 // store the 24 bit systick timer 37 *pstart = SYST_CVR & 0x00FFFFFF; 38 39 return; 40 } 41 42 // ARM-core specific function to compute the elapsed systick timer ticks for benchmarking ARM_systick_elapsed_ticks(int32 start_ticks)43int32 ARM_systick_elapsed_ticks(int32 start_ticks) 44 { 45 int32 elapsed_ticks; 46 47 // subtract the stored start ticks and check for wraparound down through zero 48 elapsed_ticks = start_ticks - (SYST_CVR & 0x00FFFFFF); 49 if (elapsed_ticks < 0) elapsed_ticks += SYST_RVR; 50 51 return elapsed_ticks; 52 } 53 ARM_systick_delay_ms(uint32 iSystemCoreClock,uint32 delay_ms)54void ARM_systick_delay_ms(uint32 iSystemCoreClock, uint32 delay_ms) 55 { 56 int32 istart_ticks; // start ticks on entry 57 int32 ielapsed_ticks; // elapsed ticks 58 int16 i; // loop counter 59 60 // loop for requested number of ms 61 for (i = 0; i < delay_ms; i++) 62 { 63 // loop until 1ms has elapsed 64 ARM_systick_start_ticks(&istart_ticks); 65 do 66 { 67 ielapsed_ticks = ARM_systick_elapsed_ticks(istart_ticks); 68 } while (ielapsed_ticks < iSystemCoreClock / 1000); 69 } 70 71 return; 72 } 73
