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LibrePilot/flight/pios/stm32f0x/pios_delay.c

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/**
******************************************************************************
* @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 */
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#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
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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)
{
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uint32_t diff = PIOS_DELAY_GetRaw() - raw;
return diff;
}
#endif /* PIOS_INCLUDE_DELAY */
/**
* @}
* @}
*/