include/bsp/spi.h

0001 /**
0002  * @file
0003  *
0004  * @ingroup raspberrypi_spi
0005  *
0006  * @brief Raspberry Pi specific SPI definitions.
0007  */
0008
0009 /*
0010  *  Copyright (c) 2014-2015 Andre Marques <andre.lousa.marques at gmail.com>
0011  *
0012  *  The license and distribution terms for this file may be
0013  *  found in the file LICENSE in this distribution or at
0014  *  http://www.rtems.org/license/LICENSE.
0015  */
0016
0017 #ifndef LIBBSP_ARM_RASPBERRYPI_SPI_H
0018 #define LIBBSP_ARM_RASPBERRYPI_SPI_H
0019
0020 #include <rtems/libi2c.h>
0021
0022 #ifdef __cplusplus
0023 extern "C" {
0024 #endif /* __cplusplus */
0025
0026 /**
0027  * @name SPI constants.
0028  *
0029  * @{
0030  */
0031
0032 /**
0033  * @brief GPU processor core clock rate in Hz.
0034  *
0035  * Unless configured otherwise on a "config.txt" file present on the SD card
0036  * the GPU defaults to 250 MHz. Currently only 250 MHz is supported.
0037  */
0038
0039 /* TODO: It would be nice if this value could be probed at startup, probably
0040  *       using the Mailbox interface since the usual way of setting this on
0041  *       the hardware is through a "config.txt" text file on the SD card.
0042  *       Having this setup on the configure.ac script would require changing
0043  *       the same setting on two different places. */
0044 #define GPU_CORE_CLOCK_RATE 250000000
0045
0046 /** @} */
0047
0048 /**
0049  * @name SPI directives.
0050  *
0051  * @{
0052  */
0053
0054 /**
0055  * @brief Setups the Raspberry Pi SPI bus (located on the GPIO header)
0056  *        on the "/dev/spi" device file, and registers the bus on the
0057  *        libi2c API.
0058  *
0059  * @param[in] bidirectional_mode If TRUE sets the SPI bus to use 2-wire SPI,
0060  *                               where the MOSI data line doubles as the
0061  *                               slave out (SO) and slave in (SI) data lines.
0062  *                               If FALSE the bus defaults to the usual
0063  *                               3-wire SPI, with 2 separate data lines
0064  *                               (MOSI and MISO).
0065  *
0066  * @retval Returns libi2c bus number.
0067  * @retval <0 Could not register the bus. See @see rtems_libi2c_register_bus().
0068  */
0069 extern int rpi_spi_init(bool bidirectional_mode);
0070
0071 /** @} */
0072
0073 #ifdef __cplusplus
0074 }
0075 #endif /* __cplusplus */
0076
0077 #endif /* LIBBSP_ARM_RASPBERRYPI_SPI_H */