/** ****************************************************************************** * @addtogroup PIOS PIOS Core hardware abstraction layer * @{ * @addtogroup PIOS_DELAY Delay Functions * @brief PiOS Delay functionality * @{ * * @file pios_delay.c * @author Michael Smith Copyright (C) 2011 * @brief Delay Functions * - Provides a micro-second granular delay using the CPU * cycle counter. * @see The GNU Public License (GPL) Version 3 * *****************************************************************************/ /* * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #include <pios.h> #include <stm32f0xx_rcc.h> #include <stm32f0xx_tim.h> #ifdef PIOS_INCLUDE_DELAY /* these should be defined by CMSIS, but they aren't */ #define DELAY_COUNTER (TIM2->CNT) /** * Initialises the Timer used by PIOS_DELAY functions. * * \return always zero (success) */ int32_t PIOS_DELAY_Init(void) { // unfortunately F0 does not allow access to DWT and CoreDebug functionality from CPU side // thus we are going to use timer3 for timing measurement RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE); const TIM_TimeBaseInitTypeDef timerInit = { .TIM_Prescaler = (48000000 / 1000000), .TIM_ClockDivision = TIM_CKD_DIV1, .TIM_CounterMode = TIM_CounterMode_Up, .TIM_Period = 0xFFFFFFFF, .TIM_RepetitionCounter = 0x0000, }; // Stop timer TIM_Cmd(TIM2, DISABLE); // Configure timebase and internal clock TIM_TimeBaseInit(TIM2, (TIM_TimeBaseInitTypeDef *)&timerInit); TIM_InternalClockConfig(TIM2); TIM_SetCounter(TIM2, 0); TIM_Cmd(TIM2, ENABLE); return 0; } /** * Waits for a specific number of uS * * Example:<BR> * \code * // Wait for 500 uS * PIOS_DELAY_Wait_uS(500); * \endcode * \param[in] uS delay * \return < 0 on errors */ int32_t PIOS_DELAY_WaituS(uint32_t uS) { uint32_t last_count = DELAY_COUNTER; while (DELAY_COUNTER - last_count <= uS) { ; } /* No error */ return 0; } /** * Waits for a specific number of mS * * Example:<BR> * \code * // Wait for 500 mS * PIOS_DELAY_Wait_mS(500); * \endcode * \param[in] mS delay * \return < 0 on errors */ int32_t PIOS_DELAY_WaitmS(uint32_t mS) { while (mS--) { PIOS_DELAY_WaituS(1000); } /* No error */ return 0; } /** * @brief Query the Delay timer for the current uS * @return A microsecond value */ uint32_t PIOS_DELAY_GetuS(void) { return DELAY_COUNTER; } /** * @brief Calculate time in microseconds since a previous time * @param[in] t previous time * @return time in us since previous time t. */ uint32_t PIOS_DELAY_GetuSSince(uint32_t t) { return DELAY_COUNTER - t; } /** * @brief Get the raw delay timer, useful for timing * @return Unitless value (uint32 wrap around) */ uint32_t PIOS_DELAY_GetRaw() { return DELAY_COUNTER; } /** * @brief Compare to raw times to and convert to us * @return A microsecond value */ uint32_t PIOS_DELAY_DiffuS(uint32_t raw) { uint32_t diff = PIOS_DELAY_GetRaw() - raw; return diff; } #endif /* PIOS_INCLUDE_DELAY */ /** * @} * @} */