Standard interface for I2C peripherals (MCU side)

openrtx/include/peripherals/i2c.h

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+/***************************************************************************
+ *   Copyright (C) 2024 by Federico Amedeo Izzo IU2NUO,                    *
+ *                         Niccolò Izzo IU2KIN                             *
+ *                         Frederik Saraci IU2NRO                          *
+ *                         Silvano Seva IU2KWO                             *
+ *                                                                         *
+ *   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, see <http://www.gnu.org/licenses/>   *
+ ***************************************************************************/
+
+#ifndef I2C_H
+#define I2C_H
+
+#include <stdint.h>
+#include <pthread.h>
+#include <stdbool.h>
+
+/**
+ * Enumeration type for I2C bus speeds
+ */
+enum I2CSpeed
+{
+    I2C_SPEED_LOW = 0,  ///< Generic, implementation-specific, low speed
+    I2C_SPEED_100kHz,   ///< Standard I2C speed
+    I2C_SPEED_400kHz,   ///< Fast I2C speed
+    I2C_SPEED_1MHz      ///< Fast Plus I2C speed
+};
+
+struct i2cDevice;
+
+/**
+ * I2C driver API.
+ */
+struct i2cApi
+{
+    /**
+     * Perform a read operation on an I2C device.
+     *
+     * @param dev: pointer to the device managing the bus.
+     * @param addr: 7-bit address of the remote peripheral.
+     * @param data: pointer to the destination buffer for data read.
+     * @param len: number of bytes to read.
+     * @param stop: set to true to send a stop condition at the end of the transfer.
+     * @return zero on success, a negative error code otherwise.
+     */
+    int (*read)(const struct i2cDevice *dev, const uint8_t addr, void *data,
+                const size_t len, const bool stop);
+
+    /**
+     * Perform a write operation on an I2C device.
+     *
+     * @param dev: pointer to the device managing the bus.
+     * @param addr: 7-bit address of the remote peripheral.
+     * @param data: data to be written.
+     * @param len: number of bytes to read.
+     * @param stop: set to true to send a stop condition at the end of the transfer.
+     * @return zero on success, a negative error code otherwise.
+     */
+    int (*write)(const struct i2cDevice *dev, const uint8_t addr,
+                 const void *data, const size_t len, const bool stop);
+};
+
+/**
+ * I2C peripheral descriptor.
+ */
+struct i2cDevice
+{
+    const struct i2cApi   *driver;     ///< Driver API
+    const void            *periph;     ///< Underlying hardware peripheral
+    const pthread_mutex_t *mutex;      ///< Mutex for exclusive access
+};
+
+
+/**
+ * Acquire exclusive ownership on an I2C peripheral.
+ *
+ * @param dev: pointer to peripheral descriptor.
+ * @return zero on success, a negative error code on failure.
+ */
+static inline int i2c_acquire(const struct i2cDevice *dev)
+{
+    if(dev->mutex == NULL)
+        return 0;
+
+    return pthread_mutex_lock((pthread_mutex_t *) dev->mutex);
+}
+
+/**
+ * Attempt to acquire exclusive ownership on an I2C peripheral.
+ *
+ * @param dev: pointer to peripheral descriptor.
+ * @return zero on success, a negative error code on failure.
+ */
+static inline int i2c_tryAcquire(const struct i2cDevice *dev)
+{
+    if(dev->mutex == NULL)
+        return 0;
+
+    return pthread_mutex_trylock((pthread_mutex_t *) dev->mutex);
+}
+
+/**
+ * Release exclusive ownership on an I2C peripheral.
+ *
+ * @param dev: pointer to peripheral descriptor.
+ * @return zero on success, a negative error code on failure.
+ */
+static inline int i2c_release(const struct i2cDevice *dev)
+{
+    if(dev->mutex == NULL)
+        return 0;
+
+    return pthread_mutex_unlock((pthread_mutex_t *) dev->mutex);
+}
+
+/**
+ * Read data from an I2C device connected on the bus managed by the peripheral.
+ *
+ * @param dev: pointer to peripheral descriptor.
+ * @param addr: 7-bit device address.
+ * @param data: pointer to a buffer where to store the received data.
+ * @param len: number of bytes to read.
+ * @param stop: if true, an I2C stop condition is generated at the end of the
+ * transfer.
+ * @return zero on success, a negative error code on failure.
+ */
+static inline int i2c_read(const struct i2cDevice *dev, const uint8_t addr,
+                           void *data, const size_t len, const bool stop)
+{
+    return dev->driver->read(dev, addr, data, len, stop);
+}
+
+/**
+ * Send data to an I2C device connected on the bus managed by the peripheral.
+ *
+ * @param dev: pointer to peripheral descriptor.
+ * @param addr: 7-bit device address.
+ * @param data: pointer to the data to be sent.
+ * @param len: number of bytes to send.
+ * @param stop: if true, an I2C stop condition is generated at the end of the
+ * transfer.
+ * @return zero on success, a negative error code on failure.
+ */
+static inline int i2c_write(const struct i2cDevice *dev, const uint8_t addr,
+                            const void *data, const size_t len, const bool stop)
+{
+    return dev->driver->write(dev, addr, data, len, stop);
+}
+
+#endif /* I2C_H */