spi.c

/***********************************************************************************
 * @file        spi.c                                                              *
 * @author      Matt Ricci                                                         *
 * @addtogroup  SPI                                                                *
 * @brief       Implements functions for SPI device interface initialization and   *
 *              communication.                                                     *
 *                                                                                 *
 * @todo        Rewrite initialisation to implement enum check for 8/16 bit mode   *
 *                          and assign approprriate function pointers                                                *
 ***********************************************************************************/
 
#include "spi.h"
 
#include "stddef.h"
 
static void SPI_send8(SPI_t *, uint16_t);
static void SPI_send16(SPI_t *, uint16_t);
 
static void SPI_receive8(SPI_t *, volatile uint16_t *);
static void SPI_receive16(SPI_t *, volatile uint16_t *);
 
static void _SPI_init(SPI_TypeDef *, SPI_Config *);
 
/* =============================================================================== */
SPI_t SPI_init(SPI_TypeDef *interface, SPI_Config *config) {
  // Early return error struct if peripheral is NULL
  if (interface == NULL)
    return (SPI_t){.interface = NULL};
 
  // Initialise SPI struct with interface
  SPI_t spi = {.interface = interface};
 
  // Update config and enable peripheral
  SPI_updateConfig(&spi, config);
 
  // Initialise remaining parameters and methods
  spi.send         = (spi.config.DFF == SPI_DFF8) ? SPI_send8 : SPI_send16;
  spi.receive      = (spi.config.DFF == SPI_DFF8) ? SPI_receive8 : SPI_receive16;
  spi.transmit     = SPI_transmit;
  spi.updateConfig = SPI_updateConfig;
 
  return spi;
}
 
// ALLOW FORMATTING
#ifndef __DOXYGEN__
 
/* =============================================================================== */
static void _SPI_init(SPI_TypeDef *interface, SPI_Config *config) {
  // Wait for any ongoing transactions to finish
  while (interface->SR & SPI_SR_BSY);
 
  // Disable peripheral and update config
  config->SPE    = false;               // Make sure SPE is disabled in config
  interface->CR1 = *(uint16_t *)config; // Update CR1 with configured values
 
  // Re-enable peripheral
  config->SPE    = true;                // Set SPE back to true
  interface->CR1 = *(uint16_t *)config; // Update CR1 with SPE enabled
}
 
#endif
 
/* =============================================================================== */
uint16_t SPI_transmit(SPI_t *spi, uint16_t data) {
  volatile uint16_t response;
  spi->send(spi, data);
  spi->receive(spi, &response);
  while (spi->interface->SR & SPI_SR_BSY);
  return response;
}
 
/* =============================================================================== */
static void SPI_send8(SPI_t *spi, uint16_t data) {
  while (!(spi->interface->SR & SPI_SR_TXE));
  spi->interface->DR = (uint8_t)data;
}
 
static void SPI_send16(SPI_t *spi, uint16_t data) {
  while (!(spi->interface->SR & SPI_SR_TXE));
  spi->interface->DR = data;
}
 
/* =============================================================================== */
static void SPI_receive8(SPI_t *spi, volatile uint16_t *data) {
  while (!(spi->interface->SR & SPI_SR_RXNE));
  *data = (uint8_t)spi->interface->DR;
}
 
/* =============================================================================== */
static void SPI_receive16(SPI_t *spi, volatile uint16_t *data) {
  while (!(spi->interface->SR & SPI_SR_RXNE));
  *data = spi->interface->DR;
}
 
/* =============================================================================== */
void SPI_updateConfig(SPI_t *spi, SPI_Config *config) {
  // Initialise config with default values if passed NULL.
  if (config == NULL) {
    config = &SPI_CONFIG_DEFAULT;
  }
 
  // Update peripheral with new config
  spi->config = *config;
 
  // Initialise SPI registers and enable peripheral
  _SPI_init(spi->interface, config);
}