SPI: driver for devices with user-provided bus transfer function
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Silvano Seva
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/***************************************************************************
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* Copyright (C) 2024 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 <errno.h>
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#include "spi_custom.h"
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int spiCustom_transfer(const struct spiDevice *dev, const void *txBuf,
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void *rxBuf, const size_t size)
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{
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const struct spiCustomDevice *spiDev = (const struct spiCustomDevice *) dev;
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const uint8_t *txData = (const uint8_t *) txBuf;
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uint8_t *rxData = (uint8_t *) rxBuf;
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if(spiDev->spiFunc == NULL)
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return -EIO;
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// Send only
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if(rxBuf == NULL)
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{
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for(size_t i = 0; i < size; i++)
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spiDev->spiFunc(dev->priv, txData[i]);
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return 0;
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}
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// Receive only
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if(txBuf == NULL)
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{
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for(size_t i = 0; i < size; i++)
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rxData[i] = spiDev->spiFunc(dev->priv, 0x00);
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return 0;
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}
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// Transmit and receive, only symmetric transfer is supported
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for(size_t i = 0; i < size; i++)
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rxData[i] = spiDev->spiFunc(dev->priv, txData[i]);
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return 0;
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}
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@ -0,0 +1,89 @@
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/***************************************************************************
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* Copyright (C) 2024 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 SPI_CUSTOM_H
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#define SPI_CUSTOM_H
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#include <peripherals/spi.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* This module allows to create an SPI device with a custom implementation of
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* the bus transfer function. An example usage is to create an SPI device using
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* an high-performance bitbanging routine.
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*/
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/**
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* Transfer single byte on the SPI bus.
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*
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* @param dev: SPI device handle.
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* @param tx: byte to be sent.
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* @return byte received from remote device.
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*/
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typedef uint8_t (*spi_func)(const void *priv, uint8_t tx);
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/**
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* Implementation of the SPI transfer function.
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*
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* @param dev: SPI device handle.
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* @param txBuf: pointer to TX buffer, can be NULL.
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* @param rxBuf: pointer to RX buffer, can be NULL.
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* @param size: number of bytes to transfer.
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* @return zero on success, a negative error code otherwise.
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*/
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int spiCustom_transfer(const struct spiDevice *dev, const void *txBuf,
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void *rxBuf, const size_t size);
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/**
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* Custom SPI device descriptor.
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*/
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struct spiCustomDevice
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{
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spi_transfer_impl transfer; ///< Device-specific implementation of the SPI transfer function
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const void *priv; ///< Pointer to device driver private data
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pthread_mutex_t *mutex; ///< Pointer to mutex for exclusive access
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spi_func spiFunc; ///< Pointer to driver configuration data.
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};
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/**
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* Instantiate a custom SPI device.
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*
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* @param name: device name.
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* @param impl: user-provided implementation of the single byte transfer function.
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* @param args: pointer to user-defined arguments.
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* @param mutx: pointer to mutex, or NULL.
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*/
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#define SPI_CUSTOM_DEVICE_DEFINE(name, impl, args, mutx) \
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const struct spiCustomDevice name = \
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{ \
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.transfer = spiCustom_transfer, \
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.priv = args, \
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.mutex = mutx, \
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.spiFunc = impl \
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};
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#ifdef __cplusplus
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}
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#endif
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#endif /* SPI_CUSTOM_H */
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