Driver for STM32F4 SPI2, with locking mechanism for concurrent access
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Silvano Seva
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/***************************************************************************
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* Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
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* Niccolò Izzo IU2KIN *
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* Frederik Saraci IU2NRO *
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* Silvano Seva IU2KWO *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 3 of the License, or *
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* (at your option) any later version. *
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* *
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* This program 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. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, see <http://www.gnu.org/licenses/> *
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***************************************************************************/
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#include "SPI2.h"
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#include <pthread.h>
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#include <stm32f4xx.h>
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pthread_mutex_t mutex;
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void spi2_init()
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{
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RCC->APB1ENR |= RCC_APB1ENR_SPI2EN;
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__DSB();
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SPI2->CR1 = SPI_CR1_SSM /* Software managment of nCS */
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| SPI_CR1_SSI /* Force internal nCS */
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| SPI_CR1_BR_2 /* Fclock: 42MHz/32 = 1.3MHz */
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| SPI_CR1_MSTR /* Master mode */
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| SPI_CR1_SPE; /* Enable peripheral */
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pthread_mutex_init(&mutex, NULL);
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}
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void spi2_terminate()
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{
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RCC->APB1ENR &= ~RCC_APB1ENR_SPI2EN;
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__DSB();
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pthread_mutex_destroy(&mutex);
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}
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uint8_t spi2_sendRecv(const uint8_t val)
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{
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SPI2->DR = val;
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while((SPI2->SR & SPI_SR_RXNE) == 0) ;
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return SPI2->DR;
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}
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bool spi2_lockDevice()
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{
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if(pthread_mutex_trylock(&mutex) == 0)
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{
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return true;
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}
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return false;
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}
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void spi2_lockDeviceBlocking()
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{
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pthread_mutex_lock(&mutex);
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}
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void spi2_releaseDevice()
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{
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pthread_mutex_unlock(&mutex);
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}
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@ -0,0 +1,69 @@
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/***************************************************************************
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* Copyright (C) 2021 by Federico Amedeo Izzo IU2NUO, *
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* Niccolò Izzo IU2KIN *
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* Frederik Saraci IU2NRO *
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* Silvano Seva IU2KWO *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 3 of the License, or *
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* (at your option) any later version. *
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* *
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* This program 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. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, see <http://www.gnu.org/licenses/> *
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***************************************************************************/
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#ifndef SPI2_H
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#define SPI2_H
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#include <stdint.h>
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#include <stddef.h>
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#include <stdbool.h>
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/**
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* Initialise SPI2 peripheral with a bus clock frequency of ~1.3MHz.
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* NOTE: this driver does not configure the SPI GPIOs, which have to be put in
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* alternate mode by application code.
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*/
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void spi2_init();
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/**
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* Shut down SPI2 peripheral.
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* NOTE: is left to application code to change the operating mode of the SPI
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* GPIOs
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*/
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void spi2_terminate();
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/**
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* Exchange one byte over the SPI bus.
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* @param val: transmitted byte.
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* @return incoming byte from slave device.
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*/
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uint8_t spi2_sendRecv(const uint8_t val);
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/**
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* Acquire exclusive ownership on the SPI peripheral by locking an internal
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* mutex. This function is nonblocking and returs true if mutex has been
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* successfully locked by the caller.
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* @return true if device has been locked.
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*/
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bool spi2_lockDevice();
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/**
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* Acquire exclusive ownership on the SPI peripheral by locking an internal
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* mutex. In case mutex is already locked, this function blocks the execution
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* flow until it becomes free again.
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*/
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void spi2_lockDeviceBlocking();
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/**
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* Release exclusive ownership on the SPI peripheral.
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*/
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void spi2_releaseDevice();
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#endif /* SPI2_H */
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