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RIOT/drivers/include/periph/spi.h

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/*
* Copyright (C) 2014-2016 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @defgroup drivers_periph_spi SPI
* @ingroup drivers_periph
* @brief Low-level SPI peripheral driver
*
* This interface defines an abstraction for using a CPU's hardware SPI units.
* The interface only supports SPI master mode.
*
* As SPI buses can have multiple devices connected to them they are to be
* considered as shared resources. To reflect this, the SPI interface is based
* on a transaction model. This requires that the bus needs to be acquired
* before usage and released afterwards, using the `spi_acquire()` and the
* `spi_release()` functions.
*
* This interface supports both software and hardware chip select lines. This is
* reflected by the cpi_cs_t type, which overloads the gpio_t type with platform
* specific values for defining platform dependent hardware chip select lines.
*
* Some devices have however very uncommon requirements on the usage and the
* timings of their chip select line. For those cases this interface allows to
* manage the chip select line manually from the user code (e.g. by calling
* gpio_set/clear explicitly) while deactivating the SPI driver internal chip
* select handling by passing @ref GPIO_UNDEF as CS parameter.
*
* In the time, when the SPI bus is not used, the SPI unit should be in
* low-power mode to save energy.
*
* The SPI unit's initialization is split into 3 parts:
* 1. `spi_init()` should be called once for each SPI unit defined by a board
* during system initialization.
* 2. `spi_init_cs()` should be called during device driver initialization, as
* each chip select pin/line is used uniquely by a specific device, i.e. chip
* select lines are no shared resource.
* 3. `spi_acquire()` needs to be called for each new transaction. This function
* configures the bus with specific parameters (clock, mode) for the duration
* of that transaction.
*
* @{
* @file
* @brief Low-level SPI peripheral driver interface definition
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
*/
#ifndef PERIPH_SPI_H
#define PERIPH_SPI_H
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <limits.h>
#include "periph_cpu.h"
#include "periph_conf.h"
#include "periph/gpio.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief Default SPI device access macro
*/
#ifndef SPI_DEV
#define SPI_DEV(x) (x)
#endif
/**
* @brief Define global value for undefined SPI device
*/
#ifndef SPI_UNDEF
#define SPI_UNDEF (UINT_MAX)
#endif
/**
* @brief Define value for unused CS line
*/
#ifndef SPI_CS_UNDEF
#define SPI_CS_UNDEF (GPIO_UNDEF)
#endif
/**
* @brief Default SPI hardware chip select access macro
*
* Per default, we map all hardware chip select lines to be not defined. If an
* implementation makes use of HW chip select lines, this value needs to be
* overridden by the corresponding CPU.
*/
#ifndef SPI_HWCS
#define SPI_HWCS(x) (SPI_CS_UNDEF)
#endif
/**
* @brief Default type for SPI devices
*/
#ifndef HAVE_SPI_T
typedef unsigned int spi_t;
#endif
/**
* @brief Chip select pin type overlaps with gpio_t so it can be casted to
* this
*/
#ifndef HAVE_SPI_CS_T
typedef gpio_t spi_cs_t;
#endif
/**
* @brief Status codes used by the SPI driver interface
*/
enum {
SPI_OK = 0, /**< everything went as planned */
SPI_NODEV = -1, /**< invalid SPI bus specified */
SPI_NOCS = -2, /**< invalid chip select line specified */
SPI_NOMODE = -3, /**< selected mode is not supported */
SPI_NOCLK = -4 /**< selected clock value is not supported */
};
/**
* @brief Available SPI modes, defining the configuration of clock polarity
* and clock phase
*
* RIOT is using the mode numbers as commonly defined by most vendors
* (https://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus#Mode_numbers):
*
* - MODE_0: CPOL=0, CPHA=0 - The first data bit is sampled by the receiver on
* the first SCK rising SCK edge (this mode is used most often).
* - MODE_1: CPOL=0, CPHA=1 - The first data bit is sampled by the receiver on
* the second rising SCK edge.
* - MODE_2: CPOL=1, CPHA=0 - The first data bit is sampled by the receiver on
* the first falling SCK edge.
* - MODE_3: CPOL=1, CPHA=1 - The first data bit is sampled by the receiver on
* the second falling SCK edge.
*/
#ifndef HAVE_SPI_MODE_T
typedef enum {
SPI_MODE_0 = 0, /**< CPOL=0, CPHA=0 */
SPI_MODE_1, /**< CPOL=0, CPHA=1 */
SPI_MODE_2, /**< CPOL=1, CPHA=0 */
SPI_MODE_3 /**< CPOL=1, CPHA=1 */
} spi_mode_t;
#endif
/**
* @brief Available SPI clock speeds
*
* The actual speed of the bus can vary to some extend, as the combination of
* CPU clock and available prescaler values on certain platforms may not make
* the exact values possible.
*/
#ifndef HAVE_SPI_CLK_T
typedef enum {
SPI_CLK_100KHZ = 0, /**< drive the SPI bus with 100KHz */
SPI_CLK_400KHZ, /**< drive the SPI bus with 400KHz */
SPI_CLK_1MHZ, /**< drive the SPI bus with 1MHz */
SPI_CLK_5MHZ, /**< drive the SPI bus with 5MHz */
SPI_CLK_10MHZ /**< drive the SPI bus with 10MHz */
} spi_clk_t;
#endif
/**
* @brief Basic initialization of the given SPI bus
*
* This function does the basic initialization including pin configuration for
* MISO, MOSI, and CLK pins. After initialization, the given device should be
* in power down state.
*
* This function is intended to be called by the board initialization code
* during system startup to prepare the (shared) SPI device for further usage.
* It uses the board specific initialization parameters as defined in the
* board's `periph_conf.h`.
*
* Errors (e.g. invalid @p bus parameter) are not signaled through a return
* value, but should be signaled using the assert() function internally.
*
* @note This function MUST not be called more than once per bus!
*
* @param[in] bus SPI device to initialize
*/
void spi_init(spi_t bus);
/**
* @brief Initialize the used SPI bus pins, i.e. MISO, MOSI, and CLK
*
*
* After calling spi_init, the pins must be initialized (i.e. spi_init is
* calling this function internally). In normal cases, this function will not be
* used. But there are some devices (e.g. CC110x), that use SPI bus lines also
* for other purposes and need the option to dynamically re-configure one or
* more of the used pins. So they can take control over certain pins and return
* control back to the SPI driver using this function.
*
* The pins used are configured in the board's periph_conf.h.
*
* @param[in] bus SPI device the pins are configure for
*/
void spi_init_pins(spi_t bus);
/**
* @brief Initialize the given chip select pin
*
* The chip select can be any generic GPIO pin (e.g. GPIO_PIN(x,y)), or it can
* be a hardware chip select line. The existence and number of hardware chip
* select lines depends on the underlying platform and the actual pins used for
* hardware chip select lines are defined in the board's `periph_conf.h`.
*
* Define the used chip select line using the @ref SPI_HWCS(x) macro for
* hardware chip select line `x` or the GPIO_PIN(x,y) macro for using any
* GPIO pin for manual chip select.
*
* @param[in] bus SPI device that is used with the given CS line
* @param[in] cs chip select pin to initialize
*
* @return SPI_OK on success
* @return SPI_NODEV on invalid device
* @return SPI_NOCS on invalid CS pin/line
*/
int spi_init_cs(spi_t bus, spi_cs_t cs);
#if defined(MODULE_PERIPH_SPI_GPIO_MODE) || DOXYGEN
/**
* @brief SPI gpio mode
*/
typedef struct {
gpio_mode_t mosi; /**< GPIO mode used for MOSI pin */
gpio_mode_t miso; /**< GPIO mode used for MISO pin */
gpio_mode_t sclk; /**< GPIO mode used for SCLK pin */
} spi_gpio_mode_t;
/**
* @brief Initialize MOSI/MISO/SCLK pins with adapted GPIO modes
*
* @param[in] bus SPI device that is used with the given CS line
* @param[in] mode a struct containing the 3 modes to use on each pin
*
* @return 0 on success
* @return <0 on error
*/
int spi_init_with_gpio_mode(spi_t bus, spi_gpio_mode_t mode);
#endif
/**
* @brief Start a new SPI transaction
*
* Starting a new SPI transaction will get exclusive access to the SPI bus
* and configure it according to the given values. If another SPI transaction
* is active when this function is called, this function will block until the
* other transaction is complete (spi_relase was called).
*
* @note This function expects the @p bus and the @p cs parameters to be
* valid (they are checked in spi_init and spi_init_cs before)
*
* @param[in] bus SPI device to access
* @param[in] cs chip select pin/line to use, set to SPI_CS_UNDEF if chip
* select should not be handled by the SPI driver
* @param[in] mode mode to use for the new transaction
* @param[in] clk bus clock speed to use for the transaction
*
* @return SPI_OK on success
* @return SPI_NOMODE if given mode is not supported
* @return SPI_NOCLK if given clock speed is not supported
*/
int spi_acquire(spi_t bus, spi_cs_t cs, spi_mode_t mode, spi_clk_t clk);
/**
* @brief Finish an ongoing SPI transaction by releasing the given SPI bus
*
* After release, the given SPI bus should be fully powered down until acquired
* again.
*
* @param[in] bus SPI device to release
*/
void spi_release(spi_t bus);
/**
* @brief Transfer one byte on the given SPI bus
*
* @param[in] bus SPI device to use
* @param[in] cs chip select pin/line to use, set to SPI_CS_UNDEF if chip
* select should not be handled by the SPI driver
* @param[in] cont if true, keep device selected after transfer
* @param[in] out byte to send out, set NULL if only receiving
*
* @return the received byte
*/
uint8_t spi_transfer_byte(spi_t bus, spi_cs_t cs, bool cont, uint8_t out);
/**
* @brief Transfer a number bytes using the given SPI bus
*
* @param[in] bus SPI device to use
* @param[in] cs chip select pin/line to use, set to SPI_CS_UNDEF if chip
* select should not be handled by the SPI driver
* @param[in] cont if true, keep device selected after transfer
* @param[in] out buffer to send data from, set NULL if only receiving
* @param[out] in buffer to read into, set NULL if only sending
* @param[in] len number of bytes to transfer
*/
void spi_transfer_bytes(spi_t bus, spi_cs_t cs, bool cont,
const void *out, void *in, size_t len);
/**
* @brief Transfer one byte to/from a given register address
*
* This function is a shortcut function for easier handling of SPI devices that
* implement a register based access scheme.
*
* @param[in] bus SPI device to use
* @param[in] cs chip select pin/line to use, set to SPI_CS_UNDEF if chip
* select should not be handled by the SPI driver
* @param[in] reg register address to transfer data to/from
* @param[in] out byte to send, set NULL if only receiving data
*
* @return value that was read from the given register address
*/
uint8_t spi_transfer_reg(spi_t bus, spi_cs_t cs, uint8_t reg, uint8_t out);
/**
* @brief Transfer a number of bytes to/from a given register address
*
* This function is a shortcut function for easier handling of SPI devices that
* implement a register based access scheme.
*
* @param[in] bus SPI device to use
* @param[in] cs chip select pin/line to use, set to SPI_CS_UNDEF if chip
* select should not be handled by the SPI driver
* @param[in] reg register address to transfer data to/from
* @param[in] out buffer to send data from, set NULL if only receiving
* @param[out] in buffer to read into, set NULL if only sending
* @param[in] len number of bytes to transfer
*/
void spi_transfer_regs(spi_t bus, spi_cs_t cs, uint8_t reg,
const void *out, void *in, size_t len);
#ifdef __cplusplus
}
#endif
#endif /* PERIPH_SPI_H */
/** @} */
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